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MONITORING AND CONTROL TACTICS FOR GRAPE ROOT BORER Vitacea
polistiformis HARRIS (LEPIDOPTERA: SESIIDAE) IN FLORIDA VINEYARDS
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
This document is dedicated to my parents, Robert and Ceil Weihman
I would, foremost, like to thank my major professor, Dr. Oscar E. Liburd, for
accepting me into his program and funding my master's research. I would also like to
thank Dr. Robert McSorley and Dr. Susan Webb for their valued participation in my
research project, the critical review of my thesis, and their availability whenever I needed
assistance. My sincere appreciation also goes out to the Small Fruit and Vegetable IPM
Lab, especially Gisette Seferina, as well as Justin Harbison and David Hoel, for their
assistance with my research. I am especially indebted to Alejandro Arevalo for his
assistance with statistics, and other computer issues-his knowledge, friendliness and
availability are second to none. Many thanks go to the Florida Grape Growers
Association for funding the research. I am especially grateful to all of the grape farmers
who allowed us to work in their vineyards as well as those who collected data for the
project. Their assistance was invaluable. Most of all I thank my parents and family for
their love and support.
TABLE OF CONTENTS
A C K N O W L E D G M E N T S ................................................................................................. iv
LIST OF TABLES ....................................................... ............ .............. .. vii
LIST OF FIGURES .................................................... .......... ................ viii
ABSTRACT ........ .............. ............. ...... ...................... ix
1 IN TRODU CTION ................................................. ...... .................
2 LITER A TU R E REV IEW ............................................................. ....................... 7
L ifecycle ................................................................ . 7
D am age ................................................................ .. ......... ...............11
M o n ito rin g ......................................................................................................12
M anagem ent H history .............................................................13
Resistant Varieties ................................. ........................... ... ...... 13
W e e d C o n tro l ................................................................................................. 14
M o u n d in g ................................................................14
Physical B arriers................................................... 15
B io c o n tro l .................................................................................................1 6
Entomopathogenic Nematodes ........................................... ..................17
M atin g D isru p tio n ......................................................................................... 19
A ttra ct-a n d -K ill ............................................................................................. 2 1
C h e m ic a l ......... ............................... ....................................................2 3
3 STATEWIDE SEASONAL DISTRIBUTION OF GRAPE ROOT BORER (GRB)
IN FLORIDA; AND THE RELATIONSHIP BETWEEN ENVIRONMENTAL
FACTORS AND CULTURAL CONTROL TECHNIQUES
A N D G R B D E N SIT Y .......................................................................................... 27
M materials an d M eth od s ......................................................................................... 2 8
Monitoring ............... ......... ................. 28
Survey ......... ......... ............................. ...............30
Environm ental factors ................. ................................ 31
Cultural conditions ............................................... ................ 32
C hem ical .................................................................................................. 33
Statistical A analysis ...................... .................. ................. ...........34
R e su lts .................................................................................................................... 3 4
M o n ito r ......................................................................................3 4
S u rv e y ..................................................................................................... 3 5
D isc u ssio n .............................................................................................................. 3 6
4 COMPARISON OF TWO TRAPS FOR MONITORING GRAPE ROOT
B O R E R P O PU L A T IO N S ...................................................................................... 55
M materials an d M eth od s .......................................................................................... 56
R e su lts ...........................................................................................5 7
D isc u ssio n .............................................................................................................. 5 8
5 MATING DISRUPTION AND ATTRACT-AND-KILL AS REDUCED-RISK
CONTROL STRATEGIES FOR GRAPE ROOT BORER IN FLORIDA ................65
M materials and M methods ....................................................69
Mating Disruption with Pheromone Twist-Ties ................................................70
Attract-and-K ill w ith Last Call-GRB ...................................... ........... ....70
Chemical Control with Lorsban .............................. ...............71
R e su lts ...........................................................................................7 1
D isc u ssio n .............................................................................................................. 7 2
6 SUMMARY AND CONCLUSIONS ............................................................... 78
L IST O F R E F E R E N C E S .............................................................................................. 82
B IO G R A PH IC A L SK E T C H ........................................................................................ 88
LIST OF TABLES
3-1 Survey questions ...................... .................... .. .. ........... .... ....... 48
3-2 First emergence, and peak emergence for 16 Florida vineyards for
2003 and 2004 by region ............................................................................ .... ... 49
3-3 2003 Grape survey results for 17 vineyards*............. ............................................50
3-4 2004 Grape survey results for 19 vineyards*............. ............................................51
3-5 Point scores for factors influencing GRB infestation severity, 2003 *................52
3-6 Point scores for factors influencing GRB infestation severity, 2004* .....................53
3-7 Correlation coefficients (r) for vineyard factors against log of total GRB
trap catch ......................................................... ................ 54
4-1 GRB trap catch totals for bucket vs. wing traps in 3 vineyards in 2003 and 5
vineyards in 2004 .......................................... ........ .............. .. 64
4-2 Total GRB trap catches, mean + SEM of weekly captures, and frequency
of weeks with zero captures for two trap types for 2003 and 2004. ........................64
5-1 Weekly mean number of grape root borers per trap for mating disruption,
attract-and-kill, Lorsban and untreated control treatments in four Florida
vineyards for 2003 and 2004 .................................. ............... ............... 77
LIST OF FIGURES
3-1 Weekly GRB trap catch for years 2003 and 2004 for four Florida Panhandle
v in ey ard s. ......................................................... ................ 4 1
3-2 Weekly GRB trap catch for years 2003 and 2004 for four North-Central Florida
v in ey ard s. ......................................................... ................ 4 2
3-3 Weekly GRB trap catch for years 2003 and 2004 for four Mid-Florida vineyards. 43
3-4 Weekly GRB trap catch for years 2003 and 2004 for four South Florida
v in ey ard s. ......................................................... ................ 4 4
3-5 Total GRB Trap Catch for 16 Florida Vineyards for the years 2003 & 2004..........45
3-6 Seasonal distribution of GRB in four regions of Florida, with the data from four
vineyards within each region pooled into one graph for the years 2003 and
2 0 04 .................................................................................4 6
3-7 Relationship between log of total trap catch (y) and sum of factor points (x)
for 2003 season ................................................. ................. 47
3-8 Relationship between log of total trap catch (y) and sum of factor points (x)
for 2004 season ................................................. ................. 47
4-1 U nitrap, or U universal M oth Trap.................................... ........................... ......... 62
4-2 W ing-style sticky trap ..................................................................... ...................62
4-3 Graphs show the GRB trap catch for bucket traps and wing traps in vineyards
FV (Alachua County), LV (Putnam County), and BH (Hillsborough County)
for the 2004 season. The vertical lines indicate the date the sticky boards
w ere ch an g ed ...................................................... ................ 6 3
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
MONITORING AND CONTROL TACTICS FOR GRAPE ROOT BORER Vitacea
polistiformis HARRIS (LEPIDOPTERA: SESIIDAE) IN FLORIDA VINEYARDS
Chair: Oscar Liburd
Major Department: Entomology and Nematology
Sixteen vineyards from four grape-growing regions across Florida were evaluated
for presence and severity of grape root borer (GRB), Vitaceapolistiformis Harris
(Lepidoptera:Sessidae), during 2003 and 2004. Grape root borer males were caught in all
vineyards, with heavier concentrations in the northern and southern counties. Grape root
borer began emerging in late June and early July in the Panhandle and southern regions.
In the north central region, emergence occurred in late July and in the central region,
mid-August. Weekly trap catches indicated that peak GRB flights occurred during mid to
late August for the Panhandle region and the second and third week of September for the
north central, central, and southern regions. Wing-style sticky traps were compared with
Universal Moth Traps (Unitraps) in order to determine which trap was more effective for
monitoring GRB activities. The Unitrap caught significantly (P < 0.05) more GRB than
the wing trap. Farmers were surveyed to determine if there was a correlation between
cultural control practices, chemical usage, and environmental conditions and total GRB
trap catch, and the results indicated a strong correlation between a combination of these
factors and the total trap catch in 2003. The results from the 2004 survey showed a
weaker correlation compared with 2003. Mating disruption and attract-and-kill (A&K)
gels were evaluated for control of GRB in Florida vineyards. For mating disruption,
pheromone twist-ties with leopard moth, Zeuzerapyrina L. (Lepidoptera:Cossidae),
pheromone were placed in vines at a rate of 254 per acre. Attract-and-kill gels containing
the GRB pheromone and a pyrethrin were applied to vine trunks at a rate of 45 grams per
acre. These treatments were compared with chlorpyrifos (Lorsban) and an untreated
control in a randomized complete block design. Two wing traps with GRB pheromone
were placed in each treatment to monitor male moth activity and determine levels of trap
shutdown. Complete trap shutdown occurred in the twist-tie section for both 2003 and
2004 suggesting disruption of mating. Both A&K and the twist-tie sections caught
significantly fewer GRB than the Lorsban treatments in 2003. In 2004, significantly
fewer moths were caught in the twist-tie and Lorsban treatments than the A&K and
untreated controls. Both A&K and mating disruption with the leopard moth pheromone
show promise as reduced-risk control strategies for GRB and warrant further study.
There are over 1,000 acres (405 ha) of grapes planted in Florida and this number is
steadily increasing. The grapes are used for fresh fruit, U-pick, jam, juice, and wine.
Florida has 13 registered wineries, producing over $8,000,000 in wine sales
(WineAmerica, 2003). In comparison with other crops, grapes are a relatively small crop
in Florida but have a strong potential for growth. Florida is the third highest wine
consuming state in the nation, and most vineyards have to import grape juice from other
states and countries to keep up with the demand. The Viticulture Advisory Council was
established in 1978 to help develop the viticulture industry in Florida, and annually gives
grants to farmers for increased grape acreage.
The primary grape grown in Florida is the muscadine (Vitis rotundifolia Michx.),
which is native to the southeastern U.S. It is well adapted to Florida conditions and does
not succumb to many diseases or pests. The American bunch grape (Vitis labrusca L) is
also native to the southeastern U. S. It is very susceptible to Pierce's disease and other
pathogens, so disease-resistant hybrids were developed (Euvitis spp.) which are now
widely planted in Florida. Euvitis is the second-most planted grape, and is used mostly
for traditional wines. The European bunch grapes (Vitis vinifera), such as Pinot Noir and
Chardonnay, have not been successfully grown in Florida, due primarily to Pierce's
The most important insect pest of grapes in Florida is the grape root borer, Vitacea
polistiformis (Harris), (Lepidoptera: Sesiidae). Grape root borers (GRB) have been
damaging vineyards in the southeastern U. S. for over 150 years (Mitchell, 1854). In the
last 40 years they have received more attention and research due to the increase in grape
acreage in many Atlantic states. The grape root borer (GRB) does not occur in
California, the principal grape-producing state in the U.S., therefore not much attention
has been afforded it. GRB infestations cause loss of vigor in grapes, serious decreases in
yields, and high vine mortality. Entire vineyards have been destroyed in Missouri (Clark
and Enns, 1964), Arkansas (Attwood and Wylie, 1963), Virginia (Virginia Tech, 2003),
South Carolina (Pollet, 1975), and Florida. In Georgia, damage and control costs totaled
$81,000 in 1997, more than any other insect pest of grapes (University of Georgia
Department of Entomology, 1997). It has been declared the most destructive insect pest
of grapes in Georgia (All et al., 1989), North Carolina (McGiffen and Neunzig, 1985),
Florida (Liburd et al., 2004) and other states.
The GRB is a difficult pest to detect and control because it spends the majority of
its lifecycle underground. It is sequestered inside grape roots, and its damage is not
readily apparent. The exposed roots of an infested vine will show tunnels just under the
cambium filled with a reddish frass and trunk girdling. The adult stage is active for only
about a week (Clark and Enns, 1964) and it is not obvious because of its resemblance to a
paper wasp of the genus Polistes (which is prevalent in summer vineyards). Damage to a
vine may not be apparent for several years. Symptoms include yellowing of leaves,
smaller leaves and berries, reduced shoot growth, dieback of portions of the vine, and
reduced yields. These symptoms occur gradually and may also be the result of other
factors. The most prominent sign of infestation is the accumulation of pupal casings that
persist at the base of vines.
Many strategies for control have been investigated, including mounding, covering
the base of vines with ground cloth, chemical control with Lorsban 4E, and mating
disruption (Olien et al., 1993). Mounding is a technique by which a layer of soil is ridged
over the base of the grape plant and under the trellis in order to prevent the adults from
emerging. Wylie (1972) showed that mounding significantly reduced GRB numbers in
an Arkansas vineyard. Mounding would not be a very effective technique to manage
GRB in muscadine grapes in Florida vineyards because the roots are easily damaged and
the vines are shallowly rooted and would quickly grow roots into the ridge. Also, Florida
has a long GRB season with bimodal emergence peaks. Subsequently, mounding would
control only a small portion of the population. To control GRB effectively using the
mounding technique, vineyards would have to be mounded several times a season and
this would be very labor intensive.
Applying ground cloth under the base of vines is another strategy used to prevent
GRB from emerging from the soil, as well as entering the root zone. This cultural control
method may also not be practical for Florida conditions. Most of the soil in Florida is
primarily loose sand, and mowers would probably dislodge and destroy the ground cloth.
Workers may also damage the ground cloth while pruning and harvesting. Similarly,
harvesting machines could also do damage when picking grapes. It may be effective in
reducing GRB numbers, and may be the best option for organic growers, but it is too
expensive, high maintenance and impractical for the average grape grower.
The conventional method of GRB control involves the use of Lorsban 4E
(chlorpyrifos), although this is not available to the hobbiest, or the unlicensed farmer.
This compound is an organophosphate, which is a class of insecticide targeted by the
Food Quality Protection Act (FQPA) of 1996 to be among the riskiest chemicals used in
agricultural systems (FQPA, 1996). Subsequently, the future use of this compound is not
guaranteed. Also, with the increase in consumer concern over pesticide usage in their
food crops, it is essential that effective IPM strategies be developed to manage GRB with
limited chemical usage. Several studies have shown Lorsban to be ineffective in control
of GRB (Wylie and Johnson, 1978; Adlerz, 1984). Lorsban can only be used once per
season and 35 days pre-harvest, which is well before the peak emergence period, and
after harvest. Since GRB emerge over a long period in Florida, and Lorsban is effective
for roughly four weeks (All et al., 1985), it cannot effectively control GRB population.
The main goal of my research was to find an effective, reduced-risk strategy for
controlling grape root borer in Florida vineyards.
Before initiating control studies, I surveyed the prevalence of GRB in Florida
vineyards to determine if farmers' cultural practices promoted or suppressed GRB
populations. Traps were placed in vineyards from different grape growing regions of
Florida and checked weekly to determine the degree of infestation and to ascertain the
time of peak emergence. Previous research by Webb et al. (1992) and Snow et al. (1991)
demonstrated peak emergence for certain areas of Florida, with longer emergences in the
more southern regions. I wanted to increase the scope of the study and reexamine the
seasonal distribution for the present era. A questionnaire was developed in order to
correlate vineyard management practices, chemical usage, local terrain, and age of
vineyards with GRB infestation levels.
In order to monitor the pest populations most efficiently, I chose to compare
pheromone-baited bucket traps with pheromone-baited wing traps. Researchers have
used both traps, but their effectiveness for catching GRB has never been compared.
In order to develop an effective control tactic for GRB in Florida, I compared the
standard, Lorsban 4E (chlorpyrifos), with the new attract-and-kill technology and with
traditional mating disruption. Mating disruption has proven to be effective in controlling
other sesiid moths, the peachtree borer (Synanthedon exitosa Say) and the lesser
peachtree borer (Synanthedon pictipes Grote and Robinson) (Yonce, 1981). It has also
shown promise for the grape root borer (Johnson and Mayes, 1980; Johnson et al., 1981;
Johnson et al., 1986; Johnson et al., 1991; Webb, 1991; Pearson and Meyer, 1996) and
warrants further investigation.
Attract-and-kill is a relatively new technology whereby insects are lured to a matrix
that contains an attractant (pheromone) and a pesticide, and subsequently killed. This
technology is selective to a target pest and safe for humans and the environment since it
involves significantly less pesticide than traditional chemical treatments (10 g of
pyrethrins per ha for GRB). Attract-and-kill has been effective in controlling codling
moth, Cydiapomonella L. (Ebbinghaus et al., 2001) as well as several other lepidopteran
pests. An attract-and-kill product for grape root borers was developed by IPM Tech
(Portland, OR) called Last Call-GRB. It contains 9% pyrethrins and 0.16% GRB
Grape farmers in Florida presently only have Lorsban to combat GRB damage to
their vineyards. Most of them are not licensed to apply this chemical, which is only
partially effective. The goal of my study is to survey and research the severity of GRB
infestations in vineyards in Florida, delineate the emergence periods, and to investigate
alternative control strategies to Lorsban. This research will show farmers the peak for
GRB emergence so that they will be better able to time their control efforts. I will also
discuss some vineyard management techniques that may help reduce infestation levels,
and give them some alternative reduced-risk strategies for controlling GRB.
The grape root borer (GRB) Vitaceapolistiformis (Harris), (Lepidoptera: Sesiidae)
is a day flying sesiid clearing moth with brown scales on the forewing, and a brown
abdomen with orange or yellow bands. Its flight behavior, buzzing sound, and
appearance resemble the paper wasp (Polistes spp.), with long legs hanging well below
the body. The males are smaller than the heavier females with four tufts of scales
extending beyond the abdomen. Most studies have reported a 2-year life cycle, although
Sarai (1972) suggests a 3-year cycle. Webb and Mortensen (1990) reported a one-year
life cycle in containerized, screen house grape plants in Florida. J.R. Meyer (North
Carloina State University, pers. comm.) also reports a predominantly one-year life cycle
in the southern end of its range. The GRB is native to the eastern United States, ranges
from Vermont across to Minnesota and east of the Mississippi River states, and occurs in
most of Florida from the Panhandle to Miami (All et al., 1987; Snow et al., 1991). They
have not been recorded in some of the major wine growing areas such as the Finger
Lakes region of New York or the southern shores of Lake Erie in New York, Ohio, and
Pennsylvania (Jubb, 1982). Their life cycle is dependent on grapes of the species Vitis,
both wild and cultivated.
The GRB is holometabolous and goes through egg, possibly six larval instars, a
pupal stage, and adult. The adults can emerge over a six-month period in Florida,
compared with < 2 months in northern states. In the southeastern U.S., GRB generally
begin flying in June or early July and continue to emerge until the weather becomes
cooler (<160C) (Snow et al., 1991). In the Florida Panhandle, emergence continues until
October, and in south Florida they can emerge until January (Webb et al., 1992). The
period of emergence may be longer in wet, cool years and shorter in hot dry years (Clark
and Enns, 1964). The grape root borer emergence is characterized by single peaks in the
northern states and variable bimodal peaks in the South (Snow et al., 1991). Prior to peak
emergence, males predominate, but the percentage of females emerging after the peak is
higher. Overall, the sex ratio over the season is about equal (Townsend and Micinski,
Adult GRB live for about eight days (Dutcher and All, 1978a). During this time
they do not feed but spend their time reproducing. The male can mate several times and
the females usually mate once. After the female emerges from her pupal case, she will
alight on a leaf or branch [weeds seem to be the favorite spot for copulation (Sarai,
1972)] and begin calling within about 30 minutes (Dutcher and All, 1978a). The virgin
female calls by lifting her abdomen and extending her pheromone gland/ovipositor,
releasing the pheromone complex (Pearson and Meyer, 1996). Males downwind are
quickly able to locate the female by this distinct chemical signal. With initial contact, the
male will touch the female with his antennae and continue to hover around her. While
hovering parallel to her and in the same direction, the male will bend his abdomen 180
degrees and insert his genitalia, thus joining at the tips of the abdomen. The male then
alights on the substrate facing the opposite direction of the female. Copulation often lasts
for about four hours and usually takes place between 1:00 and 6:00 in the afternoon
(Dutcher and All, 1978a).
The female lays her eggs within 24 hours after mating (Dutcher and All, 1978a).
During daylight hours, the gravid female lays her eggs one at a time, often a few cm
apart, on soil, the trunk, and low grape leaves and branches, but mostly on weeds near the
trunk. These eggs are then shaken down to the soil surface by wind and rain. Initially,
being heavily weighted down, GRB female lays the majority of her eggs around the
nearest trunk. She loosely attaches them with a weak adhesive secretion, and they fall to
the ground shortly thereafter. As she lightens her load, she flies to other vines to spread
her progeny. The female GRB lays an average of 354 eggs, ranging from 122-707
(Dutcher and All, 1979a). The eggs are small (1.0 mm) reddish-brown ovals with one
side convex and the other with a longitudinal groove (Bambara and Neunzig, 1977). In
the field, the eggs incubate for roughly 18.2 days. Egg survivability is 70-85% under
laboratory conditions, but undoubtedly much lower in the field (Clark and Enns, 1964).
As the first instar hatches, it immediately enters the soil in search of grape roots.
Moisture is extremely important at this stage because desiccation of the first larval instars
is a major mortality factor, and therefore dry months often result in smaller infestations
(Sarai, 1972). Abiotic factors, such as soil moisture and depth of roots, affect first-instar
mortality. Only 1.5 to 2.7% of the larvae that emerge survive to infest the roots of grape
vines (Dutcher and All, 1978b). The young GRB start feeding on the smaller roots, but
migrate towards the larger roots and crown as they grow. The first-instar is whitish and
only measures between 1.7 and 2.7 mm (Bambara and Neunzig, 1977).
The young larvae continue feeding for the rest of the season and may go through an
obligate diapause during the winter in the colder areas of its range. All et al. (1987)
indicate that in Georgia GRB are quiescent during the winter but may become active if
the soil becomes sufficiently warm. Further research is required to determine its over
wintering mechanisms in Florida.
As the larvae mature they become cream white with brown heads that are
retractable. Larvae have 3 pairs of true legs and 5 pairs of abdominal prolegs. Their
bodies are about 3-4 cm long and are sparsely covered with coarse hairs. They burrow
into the cambium layer of the root system and make tunnels, depositing a reddish-brown
frass behind them, and move in the direction of the crown (Dutcher and All, 1978c). The
more mature larvae are generally found in the larger roots and in the crown. Large
gouge-like wounds are indicative of GRB feeding.
In the early summer of their second year, after 22 months of development, the
mature larvae burrow their way to the top 5 cm of soil and begin spinning their cocoons
(3-4 cm long) of silk, frass, and soil. The cocoons are often attached to a root. The pupal
stage lasts between 26 to 45 days (Sarai, 1972). Grape root borers complete their
development after 1100 degree days, base 100 C (Johnson et al., 1981). The pupa is 1.5
to 2.5 cm in diameter. When the adult is fully developed, the pupa will wiggle 3A of the
way out of the cocoon by spiraling its body with the use of abdominal spikes, and emerge
vertically halfway above the soil. The pupal case then splits in half and the adult emerges
and climbs onto the nearest substrate to dry its wings.
The vast majority (92%) of the cocoons are found within 35 cm of the trunk
(Townsend, 1980). Small larvae are found evenly throughout the root structure and
medium and large larvae are more abundant toward the trunk and larger roots. Most
larvae are found within 5 and 20 cm of the soil surface, but they have also been
discovered as deep as 80 cm (Dutcher and All, 1978c).
The mechanisms that initiate emergence have been a subject of debate. Dutcher
and All (1978d) suggest that it is based on degree-days and the accumulation of berry
sugar (for Concord grapes). The percentage of berry sugar (>5%) correlates to the
development of pupae and percentage of adult emergence. This may be true for Georgia
and other states, but research by Webb et al. (1992) suggests that in Florida, emergence
may relate more to soil temperature and type, rainfall, and timing of changes in
nutritional quality of grape roots.
Grapes root borers attack cultivated muscadine grapes, Vitis rotundifolia Michx.,
American bunch grapes, V labrusca L., European bunch grapes, V. vinifera L., and
hybrid bunch grapes, Euvitis spp. They also live on wild grapes and spread from these
into new vineyards. If an old infested vineyard is nearby, moths populate the new
vineyard starting from the rows nearest to the old vineyard. In one study, the average
yield per vine increased on vine rows progressively farther from the old vineyard
Grape root borers damage vines by girdling the roots, cutting off nutrients and
water transfer from the roots to the rest of the plant. Extensive damage may be done
before symptoms appear. The first symptom of GRB damage is often yellowing and
wilting of the leaves, which may also result from other factors. This is followed by
reduced shoot growth, smaller leaves and berries, loss of vigor, susceptibility to freeze
damage and drought, susceptibility to pathogens, and reduced yields. In some cases,
canes will start to die off and eventually the whole plant succumbs. This may take
several seasons to become obvious. The traditional method of monitoring GRB activity,
besides digging up the vines and inspecting for larvae, is to count the pupal casings under
the vines. Monitoring male GRB with pheromone traps is another method for estimating
Studies by Dutcher and All, (1979b) show that one GRB larva feeding at the crown
can cause as much as 47% decrease in yield in a single vine, and 6 larvae can cause a
100% decrease. Although an economic threshold of 73 larvae per hectare has been
established by Dutcher and All, (1979b), a vine can withstand a high GRB population
with minimum yield loss if GRB are feeding on the lateral roots. Olien et al. (1993)
suggest that a healthy, vigorous vine should be able to grow new roots faster than GRB
can consume them. It is the destruction of the crown that causes severe yield loss and
eventual death. Harris et al. (1994), reported that older vineyards are more severely
infested and younger vines suffer less damage.
The standard trap used for monitoring GRB populations in pheromone and mating
disruption experiments has traditionally been wing-style sticky traps (Johnson et al.,
1986; Johnson et al., 1991; Snow et al., 1987; Snow et al., 1991; Webb, 1991; Webb et
al., 1992). Scientists working on other lepidopteran pests have investigated the
performance of wing traps against Universal Moth Traps (Unitraps) (Great Lakes IPM,
Vestaburg, MI). Shaver et al., (1991) compared Unitraps with 13 other trap types for
monitoring Mexican rice borer (Eoreuma loftini Dyar). In all tests, the Unitrap caught
significantly more moths than the 13 other traps including the wing trap. Schmidt and
Roland (2003) compared Unitraps with wing traps for monitoring populations of forest
tent caterpillars (Malacosoma disstria Hubner). At endemic population levels, the
Unitrap caught twice as many moths as the wing trap. At high population levels, the
wing trap became completely filled with moths and debris and became unusable after a
saturation point of about 20 moths per trap.
The grape root borer has been an elusive pest to control. Traditional control
methods in the early 20th century included scalding the cocoons with hot water, and
hoeing of cocoons to expose them to environmental conditions. It was not until the 1960s
that scientists began looking at more effective strategies.
Resistant varieties have been reported and negated since the early 1900s. It was
first thought that muscadines were resistant to GRB but that was proven to be erroneous.
Later, it was suggested that the Scuppernong variety of muscadines was also resistant to
GRB, but that was proven to be untrue (Wylie, 1972). However, it appears that a few
varieties of muscadines may show a higher degree of resistance. Harris et al. (1994)
found 'Doreen' to be highly resistant to GRB perhaps due the fact that its main roots are
smaller and more numerous, enabling it to tolerate more damage. Earlier, Wylie (1972)
investigated resistance and discovered 10 rootstocks that showed promise. Webb et al.
(1990) concluded that none of the grape rootstocks in their trial were totally resistant but
some varieties were more tolerant. They found that rootstocks that had the Florida
leatherleaf grape, V. \hinieii\ ,i d/ii, in their parentage were significantly less damaged by
GRB. Furthermore, they concluded that the roots of muscadines were often more
damaged by GRB than those of the hybrid bunch grapes, perhaps due to the fact that
muscadines are more shallowly rooted and thus more accessible to the GRB larvae.
Weeds, in general, are important to the grape root borer's lifecycle. They provide
substrate upon which to lay eggs, and are the preferred mating sites for the adults (Sarai,
1972). They also provide cover to the newly emerged adults and create a humid
environment and protection for first larval instars. The egg and first larval instars are the
most vulnerable stages of the GRB lifecycle. Research has shown that over 95% of eggs
and first larval instars are killed before they reach the roots (All et al., 1987). The
mortality of the eggs and first larval instars is due primarily to predation, environmental
extremes, pathogens, and parasites. After they have reached the roots, mortality is under
Mounding is a technique by which a layer of soil is built over the base of the grape
plant and under the trellis. This is done to prevent the adults from emerging. Grape root
borer cocoons are generally found at 3 cm under the soil surface. Sarai (1969) tested
different depths of soil to determine the depth from which the majority of GRB would not
be able to emerge. He found that 100% mortality was achieved at a depth of 7.5 inches.
However, any new larvae making their way to the surface after the soil ridge is placed at
the base of the plant would simply burrow to the top of the ridge. Timing is important
during mounding. The ridge must be placed right before the peak emergence, and since
the majority of GRB emerge within 35 cm from the trunk, the ridges should extend out
about 50 cm from the trellis wire (Dutcher and All, 1979a). In field experiments, Wylie
(1972) found 0 andl4 GRB pupal cases in two mounded test vineyards versus 71 and
134, respectively, in the controls. Later, All et al. (1985) reported 83% control of GRB
by using the mounding technique. Further work showed that, in addition to preventing
adults from emerging, mounding also created a higher rate of juvenile mortality, since the
first larval instars might starve before locating the roots (All et al., 1987). Other research
has shown that mounding not only helps with GRB, but also limits the amount of
herbicide used (Kennedy et al., 1979).
The implementation of a synthetic sheet (as a mulch) may prevent first-instar larvae
from reaching the soil, allowing them to die of desiccation. The use of a soil barrier
would also prevent adults from emerging from the soil.
Yonce (1995) used physical barriers in field studies as a means to control GRB
over a three-year period. In his studies, three different ground cloths (Weed Barrier, an
experimental polypropylene (BASF Corp., Parsippany, NJ), and the standard black
polyethylene) were compared with the control (no barrier) in a randomized block design.
No significant differences were recorded between his barrier treatments. However,
overall, infestations in the barrier treated plots showed 20-81% reduction in larval
numbers compared with the control plots. Larvae were still able to penetrate the fabric,
but it slowed down their progress, increasing the time they were exposed to the air. In
lab experiments, larvae died when exposed to air for 4-5 hours without supplemental
moisture (Townsend, 1980).
Yonce (1995) conducted similar experiments using potted grapes in the
greenhouse. Weed Barrier (a spun fabric) proved to be the most effective ground cloth,
compared with black polyethylene and an experimental polypropylene. This reduced first
larval instar penetration by 42%. In another study, Attwood and Wylie (1963) suggest
that black polyethylene will control adults from emerging by 90% for a 60 cm wide strip
and 100% for a 120 cm wide strip. But for this to be effective, the barrier has to be
installed properly and well maintained. It also has the added benefit of weed prevention,
and thus reduction of herbicide use.
There are a number of organisms that prey on grape root borers. Birds such as barn
swallows, Hirundo rustica erythrogaster Boddaert, mocking birds, Mimus polyglottus L.,
and the great crested flycatcher, Myiarchus crinitus L., have been observed eating GRB
adults (Clark and Enns, 1964). Arthropods such as firefly larvae, Photurispennsylvanica
De Geer, and soldier beetle larvae, Chauliognathuspennsylvanicus De Geer, also feed on
root borers. In a study to determine the types of predators that prey on GRB eggs,
Dutcher and All (1978b) recorded tiger beetles, Cicindellapunctulata (Olivier); ground
beetles, Calosoma sayi (DeJean), Harpaluspennsylvanicus (De Geer), and Calathus sp.,
shore flies, Notiophilus sp., and a staphylinid beetle feeding on GRB eggs. Other natural
enemies include a parasitic braconid wasp, Bracon caulicola (Gaham), which parasitizes
mature GRB larvae within the top 5 cm of soil (Dutcher and All, 1978b). Also, Clark and
Enns (1964) found chalky white GRB specimens in the field, and lab results showed that
the mortality was caused by the insect pathogenic white muscardine fungus, Beauveria
bassiana Balsamo, and green muscardine fungus, Metarrhizium anisopliae Metchnikoff.
These fungi killed GRB both in the field and in the lab (Sarai, 1972). In one vineyard in
Georgia, M. anisopliae killed seven of 12 GRB pupae in one vine (Dutcher and All,
1978b). Two other organisms that attack the pupal stage are Aspergillusflavus Link ex
Fr., a fungal pathogen, and C. pennsylvanicus, a lightning bug (Dutcher and All, 1978b).
The application of predatory nematodes of the genera Heterorhabditis and Steinernema
have also shown some promising results against GRB larvae (Williams et al., 2002).
Dutcher and All (1978b) compared two vineyards, one with regular pesticide
treatments of carbaryl (Sevin) and methyl parathion and an untreated (control) vineyard
to determine the effects of pesticides on naturally occurring biocontrol agents. They
found that egg predation by natural predators and egg hatchability were 11.6% and 25.3%
respectively in the treated vineyard, suggesting that the chemicals may have had an
ovicidal effect. Alternately, egg predation and hatchability were 61.7% and 76.38%
respectively in the vineyard that was not treated with insecticides. The total egg
mortality for the chemical site was 77.45%, compared with 66% in the untreated
vineyard, suggesting that pesticides may have an ovicidal effect. No significant
differences were found with the underground life stages. In the chemical-free vineyard,
survival for each stage was egg 22.6%, first larval instar 2.7%, root established larvae
95.8%, and pupae 92.5%, suggesting that the most vulnerable stages are egg and first
Entomopathogenic nematodes are roundworms that parasitize and infect insects and
arthropods. The nematode enters the insect through a body cavity or in some cases
directly through the body wall and enters the haemocoel. The insect dies as a result of
septicemia induced by Xenorhabdus bacteria, which has a mutualistic relationship with
the nematode, and kills the insect within 24-48 hours (Grewal et al., 1994). A single
GRB host can produce 300,000 to 400,000 nematodes. The infective stage is the third
stage juvenile, the only free living stage of growth, which locates the host and initiates
The idea of using entomopathogenic nematodes to control an insect species was
being discussed as early as 1969 (McGuire and Wylie, 1969). They recognized the
relationship ofNeoaplectana carpocapse (Weiser) (presently Steinernema) with grape
root borer. The first use of this nematode was against peach tree borer. Schmidt and All
(1978) found that the nematode dauer larvae locate their host by sensing excrement and a
chemical gradient around the host through the use of chemoreceptors.
All et al. (1981) made the first attempt at using Steinernema carpocapse to control
GRB. They discovered a strain of Steinernema carpocapse in several Concord grape
vineyards in Georgia but also noted that GRB larvae and pupae mortality was low. All et
al. (1981) reported that naturally occurring populations would not be large enough for
proper control and that introduction of high levels would be needed for effective control.
In laboratory tests, the introduction of 10,000 dauer larvae resulted in 80% mortality of
closed larvae, 76.9% mortality for one-year-old larvae, and 80% mortality for two-year-
old larvae. Nematodes began emerging from infested one and two-year-old larvae within
7-18 days at 210C. The high mortality rates were promising. The disadvantage of this
tactic is that high levels of nematodes are necessary and that GRB larvae had to be placed
near the nematodes for infection to take place. Saunders and All (1985) found that
Steinernema carpocapse was effective in killing first larval instars as they burrowed
down to their primary feeding sites, and that there was an inverse relationship between
GRB density and nematode densities. Steinernema carpocapse nematodes were found to
be the most effective in suppressing GRB activity at 290C and their survival was directly
correlated to soil temperatures (300C) and soil moisture (>79.5% R.H.) at which infective
juveniles lived for 1.5 to 2 years (Gray and Johnson, 1983).
Williams et al. (2002) did laboratory and greenhouse bioassays to determine which
species of nematodes would be most effective against GRB. Their conclusion was that
Heterorhabditis zealandica Poinar (strain XI) showed the most promise in all of the tests.
In the laboratory, H. zealandica produced an 86% infection rate, and in the greenhouse, it
produced a 53% infection rate. At a rate of 60,000 nematodes per plant, 95% mortality
was achieved. H. zealandica can also locate GRB in root pieces, and in one study caused
96% mortality. In the field, when 5 billion H. zealandica per hectare were applied, it
achieved 70% control (Pollock, 2002).
Control of GRB using entomopathogenic nematodes shows great promise and
should be investigated for Florida soils.
To initiate mating, a female grape root borer will emit a pheromone, which is
specific to her species. This is referred to as 'calling', and the male downwind will sense
it and be able to locate her. Mating disruption occurs when an area becomes saturated
with the female sex pheromone. The male, confused, is unable to locate the female and
mating does not take place. Over time, populations will decline. This has successfully
been used to reduce populations of other sesiid moths, for example, the peach tree borer,
Synanthedon exitosa (Say) and the lesser peachtree borer Synanthedonpictipes (Grote
and Robinson) in peach orchards (Yonce, 1981).
The first pheromone used for GRB was the one developed for the peachtree borer,
and the lesser peachtree borer, (Z,Z)-3,13 octadecadienyl acetate (Z,Z-ODDA). Johnson
and Mayes (1980) tested this pheromone and found it to be attractive to GRB. Later,
Johnson and Mayes (1981) evaluated it and found it to be an ineffective monitoring
device, but showing some potential in mating disruption. In further mating disruption
experiments, GRB densities declined twofold faster in plots treated with Z,Z-ODDA
using Hercon laminated dispensers than the check plots (Johnson et al., 1986). In another
experiment, Johnson et al. (1986) caged calling females in a pheromone-saturated
vineyard and also in a non-pheromone saturated vineyard (control). The former attracted
14 males while the latter attracted 127.
Schwartz et al. (1983) analyzed samples of pheromones from female GRB
ovipositor extracts and identified (E,Z)-2,13-ODDA to be the GRB pheromone. They
also acknowledged that there were probably other minor components. Snow et al. (1987)
added 1% (Z, Z)-3,13 octadecadienyl to the pheromone and found that it increased the
capture of GRB males by 3 to 7 times more than by using the major component by itself.
Johnson et al. (1991) applied the new pheromone blend using saturated Shin-Etzu ropes
(Mitsubishi Corporation, Tokyo, Japan) (254 ropes per hectare) in one vineyard and
compared it to an untreated vineyard (control). By counting the pupal skins, they noted a
reduction of 92.7% over a two-year period, whereas the check plot had an increase of
17.2% over the same period.
Webb (1991) compared a pheromone-saturated vineyard with an untreated vineyard
in Florida. The pheromone-treated vineyard produced significantly fewer pupal skins
than the control as well as trap shutdown. Also, 70% of the females caught in the control
plot had mated, whereas, in the pheromone-saturated vineyard, only 11.6% had mated. In
a more recent study, Pearson and Meyer (1996) showed that Shin-Etzu ropes were more
effective than using rubber septa in mating disruption experiments because the chemical
is dispensed over a longer period from the twist ties. Further analysis of the data showed
that in the treated vineyard with a high GRB population, the percent of females mated
was 54%, while in another treated vineyard with a low population density, it was 0%.
They concluded that mating disruption of GRB may only work when the population is
moderate to low.
Attract-and-kill (A&K) is a promising new technique for pest control. This method
employs an attractant and a toxicant. The attractant is a semiochemical, such as a sex
pheromone or a kairomone. The insect is attracted to the pheromone and is killed by the
toxicant. The pesticide in the droplet adheres to the insect cuticle, or is ingested and the
insect dies shortly thereafter, depending on the dosage and the length of exposure. One
of the benefits of using this technique is that it targets the desired insect pests and has less
detrimental effects on beneficial insects. Also, there is no spray drift with attract-and-kill
systems and no pesticide residues are left on the fruit. It is easy to apply and lesser
amounts of pesticides will be used per hectare.
Attract-and-kill treatments have been used successfully to suppress populations of
several lepidopteran pests in different crops: Spodoptera littoralis Boisduval in cotton
(De Souza et al., 1992), Epiphyas postvittana Walker in apples (Brockerhoff and
Suckling, 1999), (Suckling and Brockerhoff, 1999), Cydiapomonella L. in apples
(Ebbinghaus et al., 2001), (Ioiratti and Angeli, 2002), Amyelois transitella Walker in
almonds (Phelan and Baker, 1987), Pectinophora gossypiella Saunders in cotton,
(Haynes et al., 1986), and Plodia interpunctella Hubner in stored foods (Nansen and
Phillips, 2003). Liburd et al. (1999) showed considerable success using a similar attract-
and-kill technique for control of a dipteran pest Rhagoletis sp. in blueberries. Recently,
IPM Technologies, Inc. (Portland, OR) has developed a product called Last Call, which
combines a sex pheromone with a pesticide into a gel matrix for controlling codling moth
C. pomonella. IPM Tech reported that Last Call CM was 2-3 times more effective for
controlling codling moth than a regular spraying program (IPM Tech, 2002).
The primary goal of attract-and-kill is to kill insects before it can mate or cause
damage. However, death is not necessary for attract-and-kill formulations to be effective.
Sublethal effects such as hyperactivity, convulsions, autotomy, and paralysis will result in
the inability of the insect to fly, perceive a mate, or carry out regular behavioral mating
responses and would effectively prevent an individual from procreating (Krupke et al.,
2001). This would, of course, depend on the amount of pesticide encountered and the
length of exposure. Nansen and Phillips (2003) found that >6% permethrin
concentrations killed males within a 24-hour period, which may be sufficient time to find
and court a female. However, in toxicity tests, males encountering the attracticide
containing at least 3% permethrin were visibly affected and unable to perform normal
courtship behavior and copulation. Haynes et al. (1986) showed that pink bollworm
males who survived pesticide exposure for 24 hours were significantly less likely to
locate a pheromone source than unexposed males. In a study by Brockerhoff and
Suckling (1999), male E. postvittana exposed to attracticide were caged with virgin
females; mortality was 100% and no females were impregnated.
In addition to knockdown, impaired mating performance, and death, another
mechanism by which attract-and-kill controls pests may be traditional mating disruption.
Suckling and Brockerhoff (1999) compared treatments of no pheromone, A&K and caged
A&K droplets for E. postvittana. Trap catches in the A&K treatment were reduced by
95% compared to the control. In the caged attracticide treatment, trap catches were
reduced by 63% compared with the control, indicating that the A&K droplets may have a
mating disruption effect. When Krupke et al. (2001) compared treatments of attracticide
in different dosages (50, 100, 200, and 500 drops per ha.) for C. pomonella, they found a
dramatic reduction in the trap-catch in the treatments of 500 drops per ha compared with
other treatments, which may be the direct result of more point sources of pheromone per
Attract-and-kill may be more attractive to male GRB than the calling females.
Krupke et al., 2001 found this to be true for codling moths with Last Call CM.
Brockerhoff and Suckling (1999) also found that attracticide droplets could be more
attractive than calling females when the percentage of pheromones in the gel matrix is
higher than that of the female moth. On the other hand, it has been suggested that the
pesticide in the attract-and-kill formulation may hinder its attractiveness to male moths.
Studies of several moths indicate that there is no significant repellency in the attracticide
where pesticide is added to the matrix (De Souza et al., 1992), (Haynes et al., 1986),
(Phelan and Baker, 1987), (Suckling and Brockerhoff, 1999). Pyrethroids have a low
vapor pressure and may not be detectable until after contact.
These studies indicate that the attract-and-kill technology can perform equally or
better than chemical control. However, like mating disruption, attracticides suffer some
of the same setbacks: high pest selectivity, inverse density dependence, and immigration
of gravid females.
All and Dutcher (1977) tested 25 pesticides (contact, systemic and fumigant) using
several rates and application methods and found that only soil injection of fumigants near
the trunk base and under the trellis wire were effective in suppressing populations of
GRB. The chemicals that caused the highest mortality were ethylene dibromide (EDB)
and ethylene dichloride (EDC) when used with a pressure flow injection device.
The most vulnerable stage of the GRB was found to be first larval instar, as they
begin to burrow into the soil in search of grape roots. All et al. (1982) proposed the use
of Lorsban 4E (chlorpyrifos) (Dow Chemical U.S.A., Midland, MI) as a residual barrier
to intercept and kill the young GRB larvae as they enter the soil. This treatment provided
a 100% mortality rate to first instars for 21 days. Gas Liquid Chromatography (GLC)
analysis of soils treated with Lorsban showed that over 90% of chlorpyrifos was retained
in the 0-3 cm layer of the soil and that Lorsban maintains its toxicity in the soil for four
weeks (half life=3 weeks) (All et al., 1985).
Adlerz (1984) compared the use of fumigating with EDC and using chlorpyrifos
(Lorsban) as a soil drench. These treatments were found to be effective for muscadine
grapes but Lorsban was not effective for bunch grapes. Muscadines are shallow rooting
vines and a drench of Lorsban will reach many roots and the GRB living in them.
Research since then has focused on Lorsban since EDC and EDB are no longer registered
The use of Lorsban as a soil drench is not only effective on the first larval instars,
but it also reduces egg hatchability. However, Lorsban had no effect on the pupae or the
emerging adults (Wylie, 1972), though lab experiments proved it to be toxic to adult male
moths. Several contact insecticides have also been tested and proved to be lethal to adult
root borers, but the use of contact insecticides in vineyards would probably have little
effect on the overall population (All et al., 1985).
Currently, Lorsban 4E is recommended at 1.06 L to 378 L of water to treat 200
vines (All et al., 1987). For best results, treatments should be concentrated around the
base of the vine and under the trellis, and the area to be treated should be weed-free. One
of the problems with Lorsban is that it can only be used once per growing season and it
has a 35-day pre-harvest interval. Lorsban cannot control a heavy infestation, but it can
be used to prevent a large population from establishing. All et al. (1989) suggests
monitoring the vineyard for pupal casings. When 5 or more pupal cases are found per
100 vines, then Lorsban should be used the following year. This should be repeated until
pupal cases are at the 2% level.
It is difficult to manage GRB in Florida with Lorsban since adults fly 4 to 6 months
with two major peak emergence times. The recommended application can only kill a
small percentage of the total population. Another problem is that peak emergence
coincides with harvest in many parts of Florida; subsequently, Lorsban cannot be applied
at that time (Webb et al., 1992).
Chlorpyrifos may be taken off the market soon due to regulations resulting from the
1996 Food Quality Protection Act (FQPA, 1996). With the increased grape acreage in
Florida, increased public interest in organic foods, and the fact that Florida is the third
highest wine drinking state, there is great potential for increased grape production.
However, before growers increase their production, effective tactics must be developed to
manage GRB. Since the future for Lorsban is threatened and growers are reluctant to use
pesticides, special efforts must be made to develop an integrated approach for control of
GRB. In Georgia, our nearest neighbor, GRB accounted for 80% of all control cost and
damage losses due to arthropod pests in grapes in 1997 (University of Georgia
Department of Entomology, 1997). Certainly, effective reduced-risk strategies are
needed as an alternative to chemical treatment with Lorsban.
STATEWIDE SEASONAL DISTRIBUTION OF GRAPE ROOT BORER (GRB) IN
FLORIDA; AND THE RELATIONSHIP BETWEEN ENVIRONMENTAL FACTORS
AND CULTURAL CONTROL TECHNIQUES AND GRB DENSITY
Grape growing is a small but increasingly important part of the Florida economy
and grape acreage has increased significantly over the past several years. Florida is the
third highest wine consuming state in the United States, and visiting wineries for wine
tasting is an increasingly popular tourist activity. The largest insect deterrent to grape
(Vitis sp.) growing in the southeastern United States is the grape root borer (GRB),
Vitaceapolistiformis (Harris); (Lepidoptera: Sesiidae). It has devastated vineyards in
several states (Olien et al., 1993) including Florida (S.Webb, University of Florida, pers.
comm.). Large infestations can also weaken plants and reduce yields. The only feasible
control method currently being used is soil drenching with chlorpyrifos (Lorsban 4E). In
order for this insecticide to be effective, it must be applied during the peak emergence
period of GRB. Unfortunately, the peak emergence for GRB coincides with the period of
grape ripening for muscadines and pre-harvest interval regulations forbid Lorsban
application at these times. Although Lorsban is not highly effective in Florida, it is the
only chemical listed for control (Adlerz, 1984). Therefore, research must be done to
develop alternative methods of control for GRB. Understanding the seasonal distribution
patterns of GRB as well as the environmental factors regulating populations will be
important when developing management programs.
Snow et al. (1991) investigated the seasonal distribution of GRB and found that, in
Florida, GRB generally begin to emerge in June. Emergence continues throughout the
season until the onset of colder temperatures. Peak emergence was generally bimodal,
and sometimes had several modes. Later work by Webb et al. (1992) explored the
seasonal distribution of GRB in Florida on a larger scale, with nine vineyards, instead of
four, and corroborated the earlier findings.
In order to detect any changes that may have occurred in GRB flight patterns over a
10-year period (1993-2004), populations of GRB were monitored in the major grape-
growing regions of Florida during 2003 and 2004. In addition, a survey was conducted to
examine the relationships between population densities of GRB, environmental factors,
and cultural management techniques to determine if there are any correlations among
these factors. To do this, a survey was compiled that included age and size of vineyard,
proximity to wild grape populations, soil characteristics, as well as irrigation techniques,
weed maintenance, and chemical usage. Information was obtained on rainfall and
temperatures for the areas monitored.
Specific objectives for this research were to monitor vineyards for GRB in four
distinct regions of Florida for two years. Weekly trap catches would reveal seasonal
distribution patterns and peak emergence for GRB. Total trap catch would indicate
vineyards or regions with severe infestations. Another objective was to correlate GRB
trap catches with environmental factors and cultural control techniques in order to
ascertain if there was a relationship between certain factors or sets of factors and GRB
Materials and Methods
Pheromone monitoring of GRB was carried out in 16 vineyards in 2003 and 18
vineyards in 2004, representing four distinct regions of Florida. During 2003, sixteen
privately owned vineyards were chosen in four areas: the Panhandle (including 1
vineyard each in Washington, Calhoun, Leon, and Jefferson counties), north-central
Florida (1 vineyard in Alachua County and 3 vineyards in Putnam County), mid-Florida
(4 vineyards in Lake County), and south Florida (including 1 vineyard in Hillsborough
County, 2 in Manatee County, and 1 in Highlands County) for 2003. During 2004, two
additional vineyards in north-central Florida, one in Putnam and one in Alachua counties,
were added to the study. Vineyards were chosen based on the diversity of environmental
conditions, age, and cultural practices, and included abandoned plantings, organic farms,
mechanized modern farms and U-pick vineyards. Another important criterion in
choosing vineyards was to find farmers who were willing to cooperate with research
Four green Universal Moth Traps (Great Lakes IPM, Vestaburg, MI) baited with
female GRB pheromone (99% (E,Z)- 2,13 octadecadienyl acetate, 1% (Z,Z)- 3,13
octadecadienyl acetate) (1 mg of pheromone per septa) (Great Lakes IPM, Vestaburg,
MI) were placed in each vineyard. Traps were distributed evenly throughout each
vineyard, at least 30 m apart. A rubber septum with the female GRB pheromone was
deposited into each cage and attached at the top of each trap. Pheromone lures were
changed once per season, at the midpoint of the GRB emergence period for the specific
region (approximately 2 months). A Vaportape (Hercon Environmental, Emigsville, PA)
treated with 2,2-dichlorovinyl dimethyl phosphate was affixed to the bottom of each trap
within the bucket to kill the GRB as they became entrapped. Traps were hung from the
trellis wire about 1 to 1.5 m above the ground near a vine.
Monitoring began in June each year because Webb et al. (1992) demonstrated that
the first emergence of GRB in the regions in which we were trapping began in June or
later. Trap contents were collected weekly into labeled plastic resealable bags.
Specimens were brought back to the lab for analysis. The number of GRB, along with
other insects collected in each trap, was recorded each week. Traps were continuously
monitored until no more borers were caught. Average weekly trap catch for each
vineyard was plotted on a graph in order to display the emergence pattern for the season.
A list of questions was asked of each grape grower participating in the survey.
Questions included biological information, environmental conditions, and management
strategies, as well as general information. These questions (Table 3-1) were designed to
ascertain which conditions or cultural techniques might influence population densities of
GRB. Growers were interviewed at the end of the growing season for 2003 and 2004,
respectively. Other information obtained included weekly precipitation, average ground
temperature, and average solar radiation. This information was obtained from weather
stations closest to each vineyard from the Florida Automated Weather Network.
From these questions, certain factors were chosen to be further studied based on
whether they might favor the development of GRB or hinder its survival, based on
previous literature. The answers to these questions were then awarded numerical values
or points. Factors that favored GRB were given a positive rating, factors that had no
effect were rated neutral (0), and factors that hindered development or led to death were
given negative ratings. The ratings for each factor differed depending on the degree to
which the factor can potentially affect the GRB life cycle.
Previous literature has suggested conditions in which GRB thrive and rankings
were determined based on this (All et al., 1982; All et al., 1985; All et al., 1987; Clark
and Enns, 1964; Dutcher and All, 1978b; Dutcher and All, 1979a; Harris et al., 1994;
Sarai, 1972; Townsend, 1980). Older vineyards often have higher GRB populations (All
et al., 1987) and points were awarded on a scale of 0 5 (based on age) as follows: 2
years and under (0 points), 3 4 (1 point), 5 6 (2 points), 7 8 (3 points), 9 14 (4
points), and 15 and higher (5 points).
Larger vineyards can support higher populations and points for size were awarded
on a scale of 1 5 as follows: less than 1.2 ha (1 point), 1.3 3.1 ha (2 points), 3.2 6.0
ha (3 points), 6.1 8.4 ha (4 points), and 8.5 ha and over (5 points). GRB also feed and
over winter in wild grapes which are prevalent in forested areas in Florida; therefore
scores were assigned from 0 to 5 based on the distance of the vineyard to forests
containing wild grapes: 5 points if the vineyard was surrounded by forests and bordered
at a 10 m distance, 4 points if forests were within 100 m, 3 points if large forested areas
were within 500 m, 2 points if some forests occurred at least 1 km away, 1 point if forests
were within a 5 km radius, and 0 points if there were not any forests in the area.
It was beyond the scope of this study to analyze the soil of each vineyard so I
judged the soil characteristic and rated it on a scale of -3 to 3 based on tilth: coarse dry
sand (-3), very dry sand (-2), dry sand (-1), sand (0), sandy loam (1), loam (2), and wet
Hot dry situations can cause mortality in newly emerged larvae as they enter the
soil to find roots (All et al., 1987; Dutcher and All, 1978b; Harris et al., 1994; Sarai,
1972). Thus, soil characteristics such as low moisture retention, as well as high ground
surface temperature, high solar radiation, and low precipitation do not favor GRB
development, and received negative ratings. Wet, cool conditions in moisture retentive
soil favor GRB and were positively rated. Weather data were obtained from the Florida
Automated Weather Network (University of Florida IFAS Extension Florida Automated
Weather Network, 2004). For the average weekly precipitation: < 3.28 cm (-3 points),
3.29 3.80 cm (-2 points), 3.81 4.31 cm (-1 points), 4.32 4.81 cm (0 points), 4.82 -
5.32 cm (1 point), 5.33 5.83 cm (2 points), and > 5.84 cm (3 points). For average
ground temperature (AGT) points were awarded as follows: <26.50C (3 points), 26.6 -
27.1C (2 points), 27.2 27.70C (1 point), 27.8 28.30C (0 points), 28.4 28.90C (-1
point), 29.0 29.50C (-2 points), and > 29.60C (-3 points). Average solar radiation (ASR)
(w/m2) was rated as follows: < 159 w/m2 ( 3 points) 160 169 w/m2 (2 points), 170 -
179 w/m2 (1 point), 180 189 w/m2 (0 points), 190 199 w/m2 (-1 point), 200 209
w/m2 (-2 points), and > 210 w/m2 (-3 points).
Cultural conditions can also affect GRB populations. There are several methods
for irrigating vineyards in Florida: drip irrigation, maxi-jets, overhead sprinklers and no
irrigation system. Drip irrigation was given 5 points because it maintains the soil
moisture near the base of the vines and favors GRB, mixed use of drip and maxi-jet
irrigation was given 4 points, and maxi-jets alone 3 points. Overhead sprinklers that wet
the soil for shorter periods of time than the other systems was awarded 2 points. No
irrigation system was given -5 points.
Previous research by Harris et al. (1994) suggests that weed control is one of the
main cultural practices that farmers can implement to reduce GRB numbers in their
vineyards. Weedy conditions offer first instar larvae cooler, more humid environments
that favor survival. In addition, weeds provide oviposition sites for female GRB and
protection for eggs. Taking a visual survey of the vineyards throughout the season, I
rated the vineyards from -5 to 5 based on the percentage of weed coverage: 5 (100%), 4
(85%), 3 (70%), 2 (55%), 1(40%), 0 (25%), -1(20%), -2 (15%), -3 (10%), -4 (5%), -5
The effect that mass-trapping has on GRB is unknown. However, if many males
are taken out of the breeding pool, it will have an effect on subsequent generations.
Negative numbers were awarded to vineyards that had trapped males the previous year
and -5 points were given for having trapped the entire season. Some vineyards began
trapping late in the season and these were awarded partial points based on the duration of
trapping during GRB flight period.
Since Lorsban is the only chemical listed for control of GRB, -5 points were
awarded for its use, and 0 for no use. Partial credit was given if farmers applied the
Lorsban to portions of their vineyards. The effects of other chemicals such as herbicides,
other insecticides, and fungicides on GRB abundance have not been studied. Since most
of the GRB life cycle occurs underground, and since the adults live for only seven days,
my assumption is that these other chemicals have little direct effect on GRB abundance.
However, it is possible that predators in the system could be killed by wide scale
applications of these pesticides, so I rated their overall effect as positive, favoring the
GRB. Chemical points were awarded per application as follows: insecticides (2 points),
herbicides (1 point) and fungicides (Ipoint). These points were then added together for
all applications and rated on a scale of 0 5: no chemicals used (0 points), 1 3 chemical
points (1 point), 4 5 chemical points (2 points), 6 9 chemical points (3 points), 10 14
chemical points (4 points), and 15+ chemical points (5 points).
These ratings were added together to achieve a cumulative score called the sum of
factors, representing the effects of these factors working together. Correlation coefficients
were calculated between the logarithm of total trap catch and the sum of factors as well as
each individual factor. A linear regression was conducted on the sum of factors (SAS
Total grape root borer trap catch per week for the two years of study, 2003 and
2004, is represented in Figures 3-1 (Florida Panhandle), 3-2 (north-central Florida), 3-3
(central Florida), and 3-4 (southern Florida). The timing of the peaks of emergence
generally coincided for vineyards within the same region. Table 3-2 shows the first
emergence and peak emergence of GRB for each vineyard for the entire season for the
years 2003 and 2004. Figure 3-5 shows the total GRB trap catches for all 16 vineyards
for 2003 and 2004. Activity began the earliest, late June early July, in the northernmost
area of Florida and the southern region. GRB emerged in the north-central region in mid
to late July, and in mid-August for the mid-Florida region. GRB peak flight occurred in
the Panhandle in mid to late August for both 2003 and 2004, except for two vineyards
whose peaks occurred in early September in 2004 (Figure 3-1). For the north-central
region of Florida, peak flight occurred in the second week of September in 2003 and the
beginning of October in 2004 (Figure 3-2). In the mid-Florida region (Lake County),
peak flight mostly occurred in the third week of September (Figure 3-3). In the southern
region, GRB emergence peaked in the second and third week of September at the
vineyards nearer to the coast and on the first week of October at the inland vineyard
(vineyard BH). For 2004, the peaks occurred from late August to mid-September, with
the inland peak slightly later than the coastal peaks (vineyards BH, OM, RF) on the third
week of September (Figure 3-4). When data from the 4 vineyards in each region were
pooled into one graph for both 2003 and 2004, some interesting regional trends were
apparent (Figure 3-6). Adult GRB activity lasted for about 3 /2 months in the Panhandle
region, 4 months in North-central Florida, 3-3.5 months in mid-Florida, and 5-5.5 months
in the southern region.
Trap catches varied among vineyards and were relatively high for certain
vineyards, and quite small for others (Table 3-2). However, there was large variation in
characteristics among vineyards, including differences in size and age, and thus it is
difficult to compare totals. Lower numbers of GRB were caught in 2004 compared with
2003, but this reduction was not significantly different.
Results of the survey are shown in Table 3-3 (2003) and Table 3-4 (2004). Tables
3-5 (2003) and 3-6 (2004) represent the graded points for the answers to the survey and
the weather information for the year.
Correlations were performed between trap counts and each of the individual factors
for 2003 and 2004 (Table 3-7). During 2003, the sum of all factors had the highest r (r=
0.774) and was the most significant variable for the 2003 survey (P < 0.01). The
regression equation is log(total GRB trap catch) = 1.049 + 0.0903 x (sum of factors).
The SEM for the intercept is 0.25 and the SEM for the slope is 0.02. The regression line
for the linear regression between the sum of factor points and the log of the total season's
trap catch is shown in Figure 3-7. Trap catch also showed a significant (P < 0.05)
correlation with vineyard age.
In 2004, trap catch showed the strongest correlation with age (r = 0.539; P < 0.05).
Again, the sum of factors showed a significant correlation (r = 0.510; P < 0.05). Trap
catch also showed significant correlation with soil type (r = 0.458; P < 0.05). The linear
equation for the correlation for the sum of factors and the total GRB trap catch in 2004 is
log(totl GRB trap catch) = 1.736 + 0.0483 x (sum of factors). The SEM for the intercept
is 0.22 and the SEM for the slope is 0.02. Figure 3-8 shows the regression line for the
linear regression between the sum of factors and the square root of the total trap catch for
The results of the monitoring experiments indicate that GRB were present in all of
the vineyards studied. Variations in climate, size, age, and cultural practices made it
difficult to draw overall conclusions. However, the results were useful in showing the
general emergence patterns and peak flight activities for GRB in these four regions of
Florida. Overall, the results show that GRB begin emerging in late June/early July in the
Panhandle and southern region of the state, but emergence is later for the north-central
and central regions. The peak flights occur in late August in the Panhandle and generally
occur around mid to late September for the rest of the state. Previous research suggested
that GRB peaks were bimodal in the southern end of the GRB range (Snow et al., 1991).
Most of the peaks from this study have been single, however, a few bimodal peaks
occurred. This could be attributed to weather conditions as opposed to a true 'two-phase'
emergence. The differences between my study and earlier published information may be
due to the use of bucket traps for monitoring currently versus the wing traps used in
previous work. I often had weekly trap catch numbers from 40 to 70 per trap with highs
in the 150-170 range during peak emergence. Wing traps are incapable of capturing this
volume of moths.
The Panhandle had the highest GRB trap catch during the two years of the study.
This may be due to a richer, more moisture-retentive soil than that found lower in the
peninsula (based on information from this study). There was a slight reduction in
regional total trap catches from 2003 to 2004 as well as total GRB trap catch from 6185
in 2003 to 4781 in 2004. The number of GRB decreased in 11 of the 17 vineyards
monitored. However, vineyards would have to be monitored over a longer period of time
to show definite trends over multiple years.
The results of my trapping study will help farmers to learn the emergence time for
GRB in their region, and as a result, to optimize the timing of their Lorsban application,
and any subsequent chemicals that may be listed for the control of GRB in grapes. This
study also gives the relative emergence dates and emergence periods, so that farmers will
know when to begin monitoring, and for how long. In the Panhandle, the GRB peak
coincides with the grape harvest around the third and fourth week of August. If farmers
were to apply Lorsban 35 days pre-harvest, they would only be able to affect a small
percentage of the GRB population. This study shows that it would be best to apply
Lorsban directly after harvest in order to maximize the potential number of GRB to be
killed, and affect subsequent generations. This is also true for the three more southern
regions. Peaks mostly occur 1 to 2 weeks after grape harvest, also around the third and
fourth weeks of August, so Lorsban applications would be best timed after harvest.
Bunch grapes are ready for harvest at the end of June and throughout July,
depending on the region. The application of Lorsban will be best timed after harvest and
slightly after the peak GRB emergence for that area.
Certain factors and conditions, when combined, can favor the development of GRB
and result in high potential GRB populations. Previous work has explored the life cycle
of the GRB and has postulated that the implementation of certain cultural control
techniques can affect the GRB population. Some of the factors are uncontrollable such as
rainfall, solar radiation, and temperature, as well as age and size of vineyard. Other
factors need to be considered before choosing the vineyard site such as soil conditions
and proximity to forests where wild grapes occur. The survey results show that an
integrated approach incorporating various control strategies may be able to lower GRB
Cultural control practices such as irrigation, weed management, and chemical usage
can be adjusted. The most common and probably most effective method of irrigating
vineyards is by drip irrigation. Drip irrigation favors GRB more than other methods
since it maintains moist conditions near the root zones, for longer periods of time than
other systems. This is a reasonable assumption, although the effect that drip systems
have compared with other irrigation systems on GRB development has not been
explored. Drip irrigation is probably the most efficient system for grape production and
it is unlikely that farmers would choose a different system.
Keeping the areas under the vine clean, especially following peak GRB activity is
the primary cultural control technique over which farmers have direct control. Most
farmers control weeds with regular, scheduled applications of Round-Up (glyphosate).
With a weed-free soil surface at the base of vines, first larval instars are exposed to
predation and or desiccation from environmental extremes (Townsend, 1980). It also
exposes recently emerged adults and limits the hidden areas in which to lay eggs.
The effects of chemical usage in vineyards are unclear. There is a great body of
research that demonstrates the importance of natural enemies in controlling and
stabilizing pest species (Price, 1997). In this study, it was assumed that a high degree of
chemical usage would negatively impact the natural enemy population and favor GRB.
Also, predators are present in each vineyard ecosystem that feed on GRB (Clark and
Enns, 1964; Dutcher and All, 1978b). Based on these assumptions, the conclusion is that
heavy use of pesticides favor GRB. Unlike bunch grapes, muscadine grapes are native to
this area and thus are well adapted to many of the insects, fungi, and other pathogens that
occur in Florida. Chemical inputs are not entirely necessary, and muscadine farmers
could probably reduce or eliminate their chemical usage without harming their yields.
Growers of bunch grapes are more reliant on fungicides and other chemicals than are
farmers who grow muscadines. In a thoroughly integrated IPM system for bunch grapes,
fungicide use could probably be reduced and alternative, reduced-risk pesticides
Lorsban (chlorpyrifos) is currently the only chemical listed for use against GRB in
grapes in Florida. When applied, Lorsban has a half-life of 3 weeks, and thus can only
kill GRB for 3 weeks of the 3-5 month GRB emergence period. Although Lorsban, by
itself, is an ineffective control strategy for GRB, it can be a part of a successful IPM
program to reduce GRB populations, especially when its use is appropriately timed.
The survey shows that many factors working together can contribute to the success
or detriment of GRB. The correlation analyses showed a high correlation between the
sum of factors and the total GRB trap catch. This indicates that there is predictability in
the degree of GRB infestation and this knowledge can help farmers to realize what size
infestations to expect, and some of the control measures they can implement to help
reduce GRB damage. In addition, the age of the vineyard as well as the soil type could
individually have a significant effect on GRB populations.
S 150 2004
GRB Weekly Trap Catch
Vineyard TH 2003 & 2004
250 GRB Weekly Trap Catch
00j Vineyard HV 2003 & 2004
Ca 100 /
GRB Weekly Trap Catch
Vineyard AM 2003 & 2004
250 GRB Weekly Trap Catch
200 Vineyard LB 2003 & 2004
Figure 3-1. Weekly GRB trap catch for years 2003 and 2004 for four Florida Panhandle
250 2003 GRB Weekly Trap Catch
S 250 Vineyard GV 2003 & 2004
GRB Weekly Trap Catch
Vineyard MM 2003 & 2004
GRB Weekly Trap Catch
S 20Vineyard CM 2003 & 2004
S 50 -
GRB Weekly Trap Catch
250 Vineyard SV 2003 & 2004
0 -1-- --- I I
Figure 3-2. Weekly GRB trap catch for years 2003 and 2004 for four North-Central
GRB Weekly Trap Catch
Vineyard GE 2003 & 2004
NV V IfV VC 40 > ?> ^> F& ^ 9 o
GRB Weekly Trap Catch
Vineyard LR 2003 & 2004
V 1" 'J p' cj~ t.&' q~ 'b6 c (5 9O
GRB Weekly Trap Catch
Vineyard OB 2003 & 2004
i ^,' 2K ^c cj K B' b' c j 'r '
GRB Weekly Trap Catch
Vineyard PR 2003 & 2004
Figure 3-3. Weekly GRB trap catch for years 2003 and 2004 for four Mid-Florida
S250 2003 GRB Weekly Trap Catch
20 Vineyard BH 2003 & 2004
NV. !&Y VY V5 '?
GRB Weekly Trap Catch
250 Vineyard OM 2003 & 2004
3C~3\~3 ~3 ,~3 ,p~4o~~JB 0(Q 00 ;"` ;A A~c
B~o ~ c .4 69
'L Iv, 11 h
GRB Weekly Trap Catch
Vineyard RF 2003 & 2004
GRB Weekly Trap Catch
S250 Vineyard HS 2003 & 2004
,e ,^ .^ .^ ^> ac 9c9 c g p^ P6-
Figure 3-4. Weekly GRB trap catch for years 2003 and 2004 for four South Florida
-- -- ~ C
I I F
I FL -F
Figure 3-5. Total GRB Trap Catch for 16 Florida Vineyards for the years 2003 & 2004
TH HV AM LB SV CM MM GV GE OB PR LR BH OM RF HS
600 Florida Panhandle Vineyards
500 -2003 -
600 Central Florida Vineyards
3 500 -2003 -
O 400 2004
600 Central Florida Vineyards
U 500 2003
) 400 2004
600 Southern Florida Vineyards
o 400 7004
Figure 3-6. Seasonal distribution of GRB in four regions of Florida, with the data from
four vineyards within each region pooled into one graph for the years 2003
y = 0.0903x + 1.0495
r2 = 0.6295
P = 0.0001
Sum of factor points
Figure 3-7. Relationship between log of total trap catch (y) and sum of factor points (x)
for 2003 season.
P = 0.0260
0 2 4 6 8 10 12 14 16 18 20
Sum of factor points
Figure 3-8. Relationship between log of total trap catch (y) and sum of factor points (x)
for 2004 season.
Table 3-1. Survey questions
1. How many acres of grapes?
2. What varieties are planted? What percentage of muscadine vs. bunch grapes are
3. How old is the vineyard?
4. How many vines were replaced (or died) this year?
5. What were the yields this year?
6. What chemicals were used (application rates and times)?
7. What types of irrigation systems are used?
8. How are the weeds maintained?
9. How is the proximate land being used?
10. What other crops are grown?
11. Do you monitor for pests? By what method?
12. What grape pests have you seen? What ones do you consider a problem?
13. Do you use any cultural pest control techniques?
14. Soil type and pH?
15. When did you harvest?
16. Grape use (wine, u-pick, grape products, table)?
Table 3-2. First emergence, and peak emergence for 16 Florida vineyards for 2003 and
2004 by region
Panhandle TH Jun 25 Jul 2 Aug 20 Aug 20
HV Jun 25 Jul 2 Aug 13 Aug 27
AM Jul 2 Jul 2 Aug 27 Sep 3
LB Jun 18 Jul 2 Aug 27 Sep 3
North-central GV Jul 23 Jul 23 Sepl0 Oct 1
MM Jul 16 Jul 2 Sep 10 Oct 1
CM Aug 13 Jul 30 Sep 10 Oct 1
SV Jul 30 Jul 30 Aug 27 Sep 10
Central GE Aug 13 Aug 27 Sep 10 Oct 1
OB Aug 27 Jul 9 Sep 10 Sep 24
PR Aug 6 Sep 4 Sep 24 Sep 24
LR Aug 13 Jul 1 Sep 24 Sep 24
< Jul 2
< Jun 18
(<) indicates that GRB were caught the first week of monitoring and may have emerged
sooner than data indicates.
Table 3-3. 2003 Grape survey results for 17 vineyards*
# of % musca-
Size varie- bunch dine
Vineyard (ha) AEe ties grapes grapes
3.2 11 12
2.0 10 10
8.1 19 100
4.0 11 16
1.6 18 4
1.4 22 15
3.6 25 13
1.1 8 15
2.0 4 10
1.4 16 15
4.0 6 2
.1 13 1
26.7 18 10
4.0 6 4
1.0 4 2
4.0 13 10
to wild Soil
Weekly Weed Lorsba
Rainfall AGT ASR Irrigation coverage used
3.05 27.74 184 M, D 20% Y
3.05 27.74 184 D 0% N
4.17 26.26 188 D 20% N
4.17 26.26 188 M, D 5% N
4.70 26.52 183 O 5% N
3.30 28.74 155
3.30 28.74 155
3.30 28.74 155 I
4.17 26.70 191
3.00 27.70 184
3.96 28.02 204
3.96 28.02 204
3.96 28.02 204
5.56 27.56 206
5.56 27.56 206
5.56 27.56 206
D 10% Y(1/4)
3 19 o
HS 4.2 6 20 0% 100% 500m Sand 4.37 29.49 193 D 15% N 16 139
Average weekly rainfall is in cm. AGT is average ground temperature (C). ASR is average solar radiation (w/m2). The methods of irrigation used are
M= microjets, D= drip, 0= Overhead sprinklers, and N=none. Lorsban was either used that year (Y) or not (N) and fractions are awarded for partial coverage.
Chemical usage (see text) is a set of points awarded for each variety of pesticides used in that specific vineyard per treatment. GRB trap catch is the total number
of GRB caught per vineyard per season
Table 3-4. 2004 Grape survey results for 19 vineyards*
yard (ha) Age
TH 3.2 12
# of % bunch
wild grapes Soil types Average AGT ASR Irrigation
Loam 3.45 28.58 193
loam 3.45 28.58 193
Loam 4.55 26.67 202
Loam 4.55 26.67 202
Sand 4.70 27.1 189
Dry sand 5.59 28.35 174
10m sand 5.59 28.35 174
100m Dry sand 5.59 28.35 174
500m Dry sand 5.21 26.94 193
% Weed Lorsban Chemical GRB trap
coverage used usage catch
M, D 20%
Y 10 289
N 70% N
M, D 25% N
D 10% Y (1/4)
GE I 1.4 17
15 5% 95%
sand 5.00 28.27 192
N 0 104
5km sand 4.11 28.5 214
10m Sand 4.11 28.5 214
1km Dry sand 4.11 28.5 214
100m Loam 5.92 27.33 216
100m Sand 5.92 27.33 216
1km Wet loam 5.92 27.33 216
500m Sand 5.28 29.73 192
500m Sand 5.59 28.35 174
LV 1.2 32
4 0% 100%
5.59 28.35 174
0 10% N 3 313
*Average weekly rainfall is in cm. AGT is average ground temperature (C). ASR is average solar radiation (\ 11- ). The methods of irrigation used are
M= microjets, D= drip, 0= Overhead sprinklers, and N=none. Lorsban was either used that year (Y) or not (N), and fractions are awarded for partial coverage.
Chemical usage (see text) is a set of points awarded for each variety of pesticides used in that specific vineyard per treatment. GRB trap catch is the total number
of GRB caught per vineyard per season.
Table 3-5. Point scores for factors influencing GRB infestation severity, 2003*
distance to Soil Rainfall Weed Lorsban Chemical
Vineyards Age Size wild grapes type average AGT ASR Irrigation coverage used usage
0-5 1-5 0-5 -3-+3 -3-+3 -3-+3 -3-+3 -3-+3 -5-+5 -5-0 0-5
4 2 -3
3 1 -3
3 2 -1
3 2 -1
4 0 0
5 -1 -2
5 -2 -2
4 -1 -2
3 -1 -1
4 -2 -3
1 -2 -1
4 0 -1
-5 4 0
0 5 0
0 5 0
0 0 0
0 2 0
0 0 -2
0 0 -2
0 2 -2
-1 1 -2
0 0 0
0 1 0
0 0 0
0 5 0
0 1 0
0 2 0
0 4 0
0 5 0
*Each of 17 vineyards was rated for each factor category (from Table 3-1) using the scale ranges shown below the category title. The sum of factors is the total
score for each vineyard of all factor points added together. GRB trap catch is the total number of GRB caught per vineyard in 2003 and Sqrt GRB trap catch is
the square root of the total GRB trap catch.
Table 3-6. Point scores for factors influencing GRB infestation severity, 2004*
distance Soil Weekly
to wild type Rainfall Weed
Vineyards Age Size grapes average AGT ASR Irrigation coverage
5 15 05 +3 +3 +3 +3 +5 +5
0-5 1-5 0-5 +3 -3-+3 -3-+3 -3-+3 -5-+5 -5-+5
Lorsban Chemical previous
used usage year
-5-0 0-5 -5-0
Sum of trap Sqrt GRB
factors catch trap catch
*Each of 19 vineyards was rated for each factor category (from Table 3-2) using the scale ranges shown below the category title. The sum of factors is the total
score for each vineyard of all factor points added together. GRB trap catch is the total number of GRB caught per vineyard in 2004 and Sqrt GRB trap catch is
the square root of the total GRB trap catch.
Table 3-7. Correlation coefficients (r) for vineyard factors against log of total GRB trap catch.
Factors 2003 2004
r P-value Significance r P-value Significance
** P< 0.01 ** P< 0.01
*P < 0.05 *P < 0.05
n.s. = not significant n.s. = not significant
Age 0.533 .0276 0.539 .0172 *
Size 0.409 .1033 n.s. 0.187 .4438 n.s.
Distance to wild grapes 0.300 .2415 n.s. 0.219 .3678 n.s.
Soil type 0.467 .5860 n.s. 0.463 .0459 *
Weekly rainfall average 0.085 .7453 n.s. 0.179 .4623 n.s.
AGT 0.346 .1736 n.s. 0.014 .9596 n.s.
ASR 0.157 .5483 n.s. 0.151 .5385 n.s.
Irrigation 0.190 .4647 n.s. 0.010 .9657 n.s.
Weed coverage 0.115 .6611 n.s. 0.059 .8107 n.s.
Lorsban used 0.175 .5019 n.s. 0.020 .9637 n.s.
Chemical usage 0.298 .2457 n.s. 0.121 .6214 n.s.
Trapped previous year 0.280 .2769 n.s. 0.225 .3545 n.s.
Sum of factors 0.794 .0001 ** 0.509 .0260 *
COMPARISON OF TWO TRAPS FOR MONITORING GRAPE ROOT BORER
The grape root borer (GRB) Vitaceapolistiformis (Harris), (Lepidoptera: Sesiidae)
is the most important pest of grapes (Vitis sp.) in Florida (Liburd et al., 2004). Grape root
borers were first noticed as pests of cultivated grapes in the southeastern U.S. in 1854
(Mitchell, 1854). The larvae bore into the roots of grapevines and eventually cut off the
flow of the phloem and xylem. One to three larvae can seriously weaken the vine and
cause lowered yields. Six larvae can kill the vine, especially if they are feeding in the
crown (Dutcher and All, 1979b). Entire vineyards have been wiped out in many
Southeastern states (Olien, 1993), including Florida (S.Webb, University of Florida, pers.
comm.). The overall effects of their continued feeding on vines is not well understood,
but the weakening of the plant makes it more susceptible to freeze damage, drought, and
Several studies have focused their efforts on understanding the GRB lifecycle and
explored the potential for non-chemical control tactics. Trapping with pheromone-baited
traps has been an important tool in these studies. The discovery of sesiid sex pheromone
and more specifically GRB pheromone in the 1980s has helped advance our knowledge
of GRB greatly (Snow et al., 1987). The seasonal distribution of GRB has been widely
studied using pheromone-baited traps. The traditional trap has been the wing-style sticky
trap. This trap has been used for monitoring in all the previous pheromone and mating
disruption studies of GRB (Johnson et al., 1986; Johnson et al., 1991; Snow et al., 1987;
Snow et al., 1991; Webb, 1991; Webb et al., 1992).
The problem with wing-style sticky traps is that they become inundated with
insects and debris and need to be replaced on a regular basis in order for them to be
effective. Researchers working with other lepidopteran pests have found great success
with Universal Moth Traps (Unitraps) (Great Lakes IPM, Vestaburg, MI). These two
trap styles have been compared in studies with other lepidopteran pests, and in each
study, the Unitrap caught significantly more moths (Shaver et al., 1991; Schmidt and
The purpose of this study was to compare the effectiveness of wing-style sticky
traps with Unitraps for monitoring GRB populations in order to find the most practical
use by farmers..
Materials and Methods
This study was carried out in three sites in 2003 and expanded to five sites in 2004.
In 2003, traps were placed in three vineyards representing different area of Florida: the
Panhandle (vineyard HV) (Calhoun County), mid-Florida (vineyard OB) (Lake County),
and the south Florida (vineyard BH) (Hillsborough County). For 2004, two vineyards in
the north-central region in Putnam County (vineyard LV) and Alachua County (vineyard
FV) were added to the original three locations.
The two traps compared for this experiment were Unitraps (Figure 4-1) and wing-
style sticky traps (Figure 4-2). Both traps were baited with GRB pheromone, 99% (E,Z)-
2,13 octadecadienyl acetate and 1% (Z, Z)-3,13 octadecadienyl acetate (Great Lakes
IPM, Vestaburg, MI). Pheromone lures were changed once per season, after 8 weeks.
A Unitrap, or Universal Moth Trap, (Great Lakes IPM, Vestaburg, MI) is a plastic
bucket trap (all green) with a central lure cage containing the pheromone septa hanging at
the top, and a slippery tunnel that guides the captured moth into a lower chamber (Figure
4-1). The moth is trapped within and killed by a Vaportape (Hercon Environmental,
Emigsville, PA) treated with 2,2-dichlorovinyl dimethyl phosphate. Wing-style sticky
traps (IPM Tech, Portland, OR) are waxed paper traps with a sticky lower board (Figure
4-2). A rubber pheromone septum was placed in the center of the sticky board. Boards
were changed at six-week intervals. Both traps were hung from the trellis wires at
roughly 1.5 m above the ground, and spaced at least 30 m apart. Traps were set out at the
beginning of the GRB emergence period for each region, late June for the Panhandle and
south and early July for central regions.
In order to compare traps, 2 Unitraps and 2 wing-style traps were placed in each
vineyard in a randomized complete block design with three vineyards in 2003 and five
vineyards in 2004. Trap catches were counted and recorded weekly for the entire
emergence periods. For 2003, each of 3 vineyards had two treatments (two traps each)
with 18 weekly samples. For 2004, each of 5 vineyards had two treatments (two traps
each) with 16 weekly samples. Total number of GRB weekly captures was analyzed
using analysis of variance (ANOVA) and differences were evaluated by using a paired t-
test (a= 0.05) (SAS Institute, 2004).
For the 2003 emergence GRB period, the total trap catch was 553 (84%) for the
bucket trap and 104 GRB (16%) for wing traps (Table 4-1). Bucket traps caught
significantly more GRB (P < 0.05), five times as many, than the wing trap on a weekly
basis (df= 1, 106; t = 1.99; P = 0.0020) (Table 4-2). In 2004, bucket traps caught 884
GRB (66%) and wing traps caught 455 (34%) (Table 4-1). Bucket traps captured
significantly more GRB per week ( P <0.05), but to a lesser degree than in 2003 (df=
1,158; t = 1.98; P = 0.0392) (Table 4-2). The percentage of zero trap captures was lower
in bucket traps than in wing traps (Table 4-2). Figure 4-3 shows the weekly GRB trap
captures for bucket and wing traps for the three vineyards in the study with the highest
GRB densities. The vertical lines on the second and third graphs in Figure 4-3 indicate
the dates the sticky bottoms of the wing traps were changed. It is evident from the graphs
that the number of trap catches decreases with the age of the sticky board in wing traps.
Bucket traps recovered significantly more GRB than the wing traps over the entire
season. This was true for all individual vineyards except one, (vineyard HV in 2004).
The reason why wing traps caught more GRB than bucket traps on this farm is unknown
but may be due to trap placement.
The poorer performance of the wing traps may be due to the fact that they become
saturated with GRB, other insects, and plant debris over the period of their use. This
reduces the sticky surface and diminishes the effectiveness of the trap over time. This is
shown in Figure 4-3, which shows a decrease in trap captures with each successive week
and an increase in trap captures with each replacement. Also, the wing trap treatments
had higher percentages of zero counts than the Unitraps, with 62.2% and 53.2% of their
weekly counts as zeros, compared with 33.7% and 41.6% respectively for bucket traps.
The weeks with zero counts occurred more often later in the six-week period when the
traps were saturated, rather than earlier when the traps were fresh. When one compares
the number of GRB caught on the first and second week after changing the sticky board
to bucket trap counts, the wing trap caught slightly more insects at these times, although
not significant (P>0.05). This experiment was designed to find a practical way for
farmers to monitor for GRB. Changing sticky boards on a weekly basis is impractical for
most vineyard operations, especially for large acreages, so a 6-week interval was chosen
for sticky board replacement. Some studies suggest that the wing trap may be more
effective at low population densities, but Schmidt and Roland (2003) showed that not to
be true for forest tent caterpillar Malacosoma disstria Hubner. Most importantly, in my
monitoring experiment, I often had weekly trap catch numbers in the bucket traps from
40 to 70 with highs in the 150-170 range during peak emergence and wing traps are
incapable of capturing this volume of moths. The wing trap can be an effective
monitoring device, but it must be changed weekly and changed daily during periods of
high activity. Clearly, the bucket trap is the superior trap for GRB, for use by growers.
Several factors may contribute to the greater effectiveness of bucket traps. Perhaps
the greater success of the bucket trap can be attributed to the more open design. The
pheromone cage at the top allows the plume to be dispensed relatively uninterrupted
whereas the wing trap is closed on two sides, and this may distort the plume structure.
The Unitrap's success may also be attributable to its trapping method. The moths are
trapped within a lower enclosure and killed quickly by the Vaportape. Moths trapped on
sticky boards have greater opportunity to escape via other debris, autotomy, or perhaps
being near the edge.
In addition to its greater efficiency, the bucket trap may be more cost-effective in
the long run. The Unitrap is the more expensive trap initially, at $8.95 per trap (Great
Lakes IPM, Vestaburg, MI), whereas the wing trap is only $2.32 per trap (IPM Tech,
Portland, OR). However, Unitraps are more durable and can be used year after year.
They are easy to assemble and are placed in the field once per season. The frequency at
which the wing traps would have to be changed would make them more expensive than
bucket traps over time. Due to the volume of wing traps needed per season, they would
be far more costly to use, not only due to the price of the traps, but also in labor.
For monitoring purposes, the Unitrap is easier to use and gives a more accurate
insect count as shown by the current data. A saturated sticky board is often difficult to
count; exposure to the elements leads to rapid deterioration. Predators, such as lizards
and frogs, are often observed on the sticky boards, along with partially eaten GRB. Frogs
would often be found living in the wing trap; it is unknown how many of the potentially
trapped insects were consumed. Frogs and other predators were found in the Unitraps
also, but not to the extent of the wing traps, and they were usually killed by the
Vaportape. Jumping spiders, Phidippus regius (Araneae: Salticidae), were the primary
predators found within the bucket traps. They did not affect counts since they left the
dried insect husk of their prey. The only problem with the jumping spiders was that they
would often lay their web-encased eggs at the lower end of the funnel, which would
prevent GRB from getting captured.
The trap used in this study was all green in color. Shaver et al. (1991) caught
significantly more Mexican rice borers Eoreuma loftini (Dyar) with green-yellow-white
traps than with all green. Future studies should focus on trap colors and distance apart.
The results of this comparison of wing traps vs. bucket traps should be useful to
farmers, crop consultants, and scientists. It is concluded that bucket traps were
significantly more efficient at capturing grape root borers in vineyards than traditional
wing-style traps. In addition to their greater efficiency, Unitraps are easier to manage,
less time-consuming, and more cost-effective.
Figure 4-1. Unitrap, or Universal Moth Trap
Figure 4-2. Wing-style sticky trap
GRB Bucket Trap Catch for Vineyards FV, LV, and BH in 2004
4\ )\ ob "?
GRB Wing Trap Catch for Vineyards FV and LV in 2004
GRB Wing Trap Catch for Vineyard BH in 2004
)> ,S ^SZ "SZ > 0 P 0 q s-& &C & & &C,
Figure 4-3. Graphs show the GRB trap catch for bucket traps and wing traps in vineyards
FV (Alachua County), LV (Putnam County), and BH (Hillsborough County)
for the 2004 season. The vertical lines indicate the date the sticky boards were
m mI i
Table 4-1. GRB trap catch totals for bucket vs. wing traps in 3 vineyards in 2003 and 5
vineyards in 2004
Total GRB catch
Vineyard Trap type 2003 2004
HV Bucket 156 32
Wing 25 73
OB Bucket 11 24
Wing 3 0
BH Bucket 386 420
Wing 76 118
FV Bucket -- 211
Wing -- 148
LV Bucket -- 197
Wing -- 116
Totals Bucket 553 884
Wing 104 455
-- indicates vineyards that were not sampled in 2003
Table 4-2. Total GRB trap catches, mean SEM of weekly captures, and frequency of
weeks with zero captures for two trap types for 2003 and 2004.
Trap Catch Weekly mean Zero frequency (%)
Trap type 2003 2004 2003 2004 2003 2004
Bucket 553 884 10.24 2.55 A 11.05 2.33 a 33.7% 41.6%
Wing 104 455 01.93 0.63 B 05.69 1.11 b 62.2% 53.2%
Weekly mean trap catch for 2003 (t = 1.99; df = 1, 106; P = 0.002) and 2004 (t = 0.98; df = 1,158; P =
0.0392) using t-pairwise comparison (a=0.05). Treatments with capital letters represent differences for
2003 and lower-case letters represent differences for 2004.
MATING DISRUPTION AND ATTRACT-AND-KILL AS REDUCED-RISK
CONTROL STRATEGIES FOR GRAPE ROOT BORER IN FLORIDA
In recent years, the public has been getting more concerned over the use of
pesticides. Their concern is not strictly over pesticide residues in their foods, but also
with environmental contamination due to the heavy use of pesticides in agricultural
systems. Today, many farmers are reducing or eliminating the use of chemicals in order
to meet consumers' demands. Furthermore, the Food and Drug Administration, through
several programs including the 1996 Food Quality Protection Act has been phasing out
some of the more dangerous chemicals. New integrated pest management techniques
must be developed to reduce pest populations without the use of traditional pesticides.
The key pest of grapes (Vitis spp.) in Florida is the grape root borer, Vitacea
polistiformis (Harris), (Lepidoptera: Sesiidae) (Liburd et al., 2004). The larvae bore into
the roots and cut off the nutrient flow, and can result in girdling of the vine. In mild
infestations, the vines become weakened and the yields decrease. In severe cases, entire
vineyards are lost (Dutcher and All, 1979b). Traditionally, chlorpyrifos (Lorsban 4E) has
been used as a soil drench to control burrowing larvae and newly emerged adults.
Lorsban is a dangerous organophosphate and is suspected of being carcinogenic (Food
Quality Protection Act, 1996). Previously, the 4E formulation was a restricted pesticide,
and farmers needed an application license in order to use it. Recently, the 4E formulation
was replaced by the safer 75 WG, but many farmers in Florida are uncomfortable using
it, and choose to not use chemical control measures. As a result, GRB have become a
serious threat to the Florida grape industry and feasible, alternative control methods need
to be investigated.
The potential for modifying an insect pest's behavior through the use of
pheromones in order to control its impact on a crop has been investigated widely in the
last 30 years (Carde and Minks, 1995). This approach has great promise in managing
GRB and other lepidopteran pests, especially through the use of mating disruption and
Mating disruption is a control strategy that has been quite successful for other
lepidopteran pests. It was first proved to be successful in controlling cabbage looper
moths- Trichoplusia ni (Hubner) at the University of California-Riverside (Shorey et al.,
1967). Since then, it has been used successfully with pink bollworm Pectinophora
gossypiella (Saunders), oriental fruit moth Grapholita molesta (Busck), tomato pinworm
Keiferia lycopersicella (Walsingham), light brown apple moth Epiphyaspostvittana
(Walker), and the codling moth Cydiapomonella L., as well as others (Carde and Minks,
1995). Among the sesiids, some success has been obtained in mating disruption with the
currant clearing moth Synanthedon tipuliformis (Clerck) (Carde and Minks, 1995), the
peachtree borer Synanthedon exitosa (Say) and the lesser peachtree borer S. pictipes
(Grote and Robinson) (Yonce, 1981).
There is still some debate of how mating disruption works. Bartell (1982)
proposed five mechanisms and suggested that mating disruption occurs most often as a
result of false trail following and sensory fatigue caused by habituation. Both
mechanisms result in sensory fatigue, but the means are different. In sensory adaptation,
as an insect is exposed to a constant source of odor, the output of the insect's olfactory
receptors declines within a few seconds, but is quickly restored once the stimulus is
removed. Habituation occurs in the central nervous system and results in the decline in
the insect's behavioral response to a repeated or prolonged stimulus. The recovery occurs
slowly, beginning many minutes to several hours after the stimulus is removed. Both are
dependent on the concentration of pheromone, and the result of both is sensory fatigue.
False trail following occurs when males lock on to the plume of the lure and expel mating
energy following false leads. Practically, this works by placing many more sources of
pheromone emissions per acre than the probable numbers of naturally occurring females
in the system. The male will spend its mating energies tracking the false females. The
odds are greater that it will find the artificial source more times than the virgin female
and will die before it encounters the female and successfully mates. To be effective, the
potency of the pheromone has to be equal to that of the female, or greater. However,
disruption will most likely occur as a result of several of these mechanisms working at
the same time. Mating disruption shows great potential as a viable control method for
GRB; it is non-harmful to the environment and is permitted by organic growing
Several studies have shown promising results for disruption of mating for grape
root borers. Pearson and Meyer (1996) affixed 254 dispensers per ha in vineyards over
four years and found a significant reduction in mated females compared with untreated
controls: 54% mated in 1988, 0% mated in1989, 0% mated in 1990, and 15.8% mated in
1991. Webb (1991) explored the control of GRB by mating disruption in Florida and
recorded a significant reduction in trap-catch, mated females, and pupal case counts (in
the following two years) compared with the untreated control, indicating a high degree of
In most successful cases, mating disruption employs the target insect's complete
pheromone blend. Some studies suggest that off-blends (partial mixtures or off-ratios)
might, in fact, work better at disruption of mating than the synthetic pheromone that is
most similar to the natural pheromone (Minks and Carde, 1988). The authors suggest
that the mechanism by which off-blends might work is by camouflaging the female
pheromone, rendering it indistinguishable from the background. Another way in which
off-blends may function is by creating a sensory imbalance in which the male becomes
attuned to the more predominant off-blend, and the ratio in the true blend is interpreted as
unnatural (Bartell, 1982).
Before the development of the current GRB pheromone, earlier work with mating
disruption of grape root borer was carried out with the peachtree borer pheromone (Z,Z-
3,13-ODDA). This ingredient is the minor component, or 1% of the current GRB
pheromone which contains 99% E,Z-2,13-ODDA. Mating disruption experiments by
Johnson and Mayes (1980), Johnson et al. (1981), Johnson et al. (1986) were performed
using Z,Z-3,13-ODDA alone and all resulted in significant reduction of GRB. Johnson et
al. (1991) found 99.1% reduced trap-catches for vineyards saturated with E,Z-2,13-
ODDA and 87.5% reduced trap-catches for the Z,Z-3,13-ODDA treatment, as well as
significantly reduced pupal skin counts compared to untreated controls. Pearson and
Meyer (1996) compared the use of single ingredients to the complete blend and
concluded that the individual ingredients were more effective at mating disruption for
GRB than the complete blend.
Attract-and-kill (A&K) is a promising new technology that involves an attractant,
such as a pheromone, and a toxicant. Unlike mating disruption, which functions by
confusing the insect, attract-and-kill technology attracts the insect to a pesticide laden gel
matrix and the insect makes contact with the pesticide (toxicant) before it is killed. The
attracticide droplet contains small amounts of pheromone so that they can attract male
moths rather than cause mating disruption. It has been successfully used on several
lepidopteran species including codling moth (Ebbinghaus et al., 2001), and Oriental fruit
moth (Evenden and McLaughlin, 2004), among others. Recently, IPM Tech (Portland,
OR) developed an attracticide for grape root borer, called Last Call-GRB. This had not
previously been tested under field conditions.
For these reasons, I decided to compare the use of attract-and-kill with traditional
mating disruption for control of the GRB.
Materials and Methods
Four vineyards were chosen for this experiment, one from each of the major grape-
growing areas of Florida: Altha (Panhandle), Palatka (north-central Florida), Fruitland
Park (central Florida), and Lithia (south Florida). Each vineyard was sampled in 2002 to
determine the occurrence of GRB. All vineyards consisted of muscadine grapes (Vitis sp)
and all farmers implemented similar management practices. No other vineyards occurred
within 16 kilometers, but wild grapes were nearby. Each vineyard was divided into four,
one-acre (0.4 ha) treatments: 1) Mating disruption with pheromone twist-ties (Shin-Etsu
Chemical Co. Ltd. Tokyo, Japan), 2) Attract-and-kill with Last Call-GRB, 3) Chemical
control with chlorpyrifos (Lorsban 4E) (Dow AgroSciences LLC, Indianapolis IN), and
an untreated control. Buffer zones between treatments were on average 15 m apart. This
experiment was initiated in the 2003 grape-growing season and repeated for the 2004
season. Grape root borers begin emerging at different times of year for different regions,
so experiments were initiated at different times.
Mating Disruption with Pheromone Twist-Ties
Pheromone twist-ties emitting the leopard moth Zeuzerapyrina L. (Lepidoptera:
Cossidae) pheromone (95% E,Z-2,13-ODDA: 5% E,Z-3,13-ODDA) (70 mg of chemistry
per unit) were applied to one-acre (0.4 ha) treatment plots at a rate of 254 dispensers per
acre (625 per ha), approximately one twist-tie per vine. Because it was possible to cause
mating disruption using individual ingredients, and the fact that the leopard moth Zeuzera
pyrina pheromone contained the major component and it was commercially available and
significantly cheaper, we chose to use an off-blend for our mating disruption experiment.
Leopard moth pheromone shares the same major component with the GRB, although a
smaller percentage (95% rather than 99%), and has a different minor component. This
pheromone has not been tested in GRB mating disruption experiments previously. The
dispensers were evenly distributed throughout the plot, and hung from the vine near the
trellis wire at roughly 1 to 1.5 meters above the ground.
Attract-and-Kill with Last Call-GRB
Last Call-GRB contains 0.16% GRB pheromone, 6.0% pyrethrins (CAS 8003-34-
7), and 93.984% inert ingredients. The rate of application is 1.59 oz per acre (112.5
grams per ha), which is equal to 900 drops per acre (2250 drops per ha) (each drop =
50[l) To achieve a uniform distribution of drops, the 900 drops were divided by the
number of vines per acre in each vineyard. So roughly 2, 3, or 4 drops were applied to
each vine depending on the total number of vines per treatment area. Last Call-GRB
drops were applied through a calibrated hand pump to the trunks of vines. Drops were
distributed on the trunk from 0.5 to 1.5 meters (near the trellis wire) from the ground.
Attract-and-kill was reapplied every 6 weeks for the duration of the season (roughly three
times per season).
Chemical Control with Lorsban
Lorsban 4E (chlorpyrifos) (44.9% a.i.) was applied once per season at the labeled
rate of 1.06 L to 378 L of water to treat 200 vines. It was applied post-harvest, coinciding
to the allowable time (under the pesticide application restrictions) closest to the period of
greatest GRB emergence. In the Panhandle, it was applied 35 days pre-harvest.
Experimental design was a randomized complete block with four replicates. Each
block was a vineyard from a distinct grape-growing region of Florida. Two wing-style
sticky traps were placed in each treatment at least 20 m apart. Trap catches were counted
weekly and recorded from the initiation of the project until the end of the GRB flight
period for each region. Total number of GRB captures was analyzed using analysis of
variance (ANOVA) and differences among means were determined by a Tukey's
multiple comparison procedure (P < 0.05) (SAS Institute, 2004).
In 2003, the mean number of male moths captured in wing traps in the area treated
with mating disruption was significantly (P < 0.05) fewer than the untreated controls and
the Lorsban treatments, and showed no statistical difference from the attract-and-kill
treatment, F = 9.81; df= 3, 264; P < 0.0001 (Table 5-1). Wing traps deployed in the
attract-and-kill areas caught significantly fewer adult male moths than traps deployed in
the Lorsban sections with no differences than the untreated controls. There were no
significant differences (P < 0.05) in trap catches between the Lorsban and the untreated
In 2004, the pheromone twist-tie treatments caught significantly (P < 0.05) fewer
GRB than the attract-and-kill and untreated control sections, and showed no differences
(P < 0.05) from the Lorsban treatments, F= 11.42; df = 3,234; P < 0.0001. There were
no differences between the attract-and-kill and the untreated control sections.
Trap shutdown was used to measure moth activity throughout the vineyard and
consequently, mating disruption success. If the males were not able to locate the female
pheromone in a trap, it is assumed that it would be unlikely for them to find a calling
female. In an experiment by Webb (1990), males were unable to locate caged calling
females in traps in a vineyard saturated with synthetic pheromone. Complete trap
shutdown was achieved in all of the pheromone twist-tie treatments for both years,
indicating that males were unable to orient to the female pheromone source; therefore it is
reasonable to assume that disruption of mating occurred. It should be noted that trap
shutdown alone does not prove that mating disruption has occurred. Previous studies
confirmed mating disruption success in pheromone-saturated vineyards by determining if
males could locate caged calling females, counting pupal skins, production of fertile or
infertile eggs by females caught within the vineyards, and trap shutdown. The mating
disruption study of GRB by Webb (1990) showed a significant degree of mating
disruption by trap shutdown as well as the reduction of pupal skin counts indicating a
correlation between the two. Johnson et al. (1991), and Yonce (1981) also showed a
correlation between reductions of pupal skin counts and trap shutdown.
Mating disruption prevents most mating of GRB moths but it is possible that some
mating may still occur. The greater problem with mating disruption is that this technique
does not prevent immigration of gravid females from nearby wild grapes. A study by
Pearson and Schal (1999) suggests that the female pheromone might attract mated
females from nearby plantings and wild grapes into the treated area. This occurred for
the squash vine borer Melittia cucurbitae Harris; females were attracted in greater
numbers to pheromone saturated plots than to the controls (Pearson, 1995). In field
observations, behavioral responses of calling females were altered in the presence of the
synthetic stimuli, with changes in calling heights, times, and movements, and increased
wing fanning and gland dragging. Johnson et al. (1986) observed gravid females flying
into pheromone treated plots from control plots to oviposit. This behavior was also
observed for the peachtree borer, Synanthedon exitosa Say in a pheromone-saturated
peach orchard (Snow et al., 1985). This perceived intraspecific competition under mating
disruption might cause females to disperse and mate elsewhere, but return to oviposit. It
is unknown what effect immigrating GRB have on treatments, and what proportion they
have in comparison with localized emerging GRB. There was a high degree of variation
between vineyards and it is difficult to draw conclusions. More research is needed on
female response to synthetic pheromone saturated vineyards. Nevertheless, mating
disruption can decrease GRB populations and yearly twist-tie deployments should be able
to reduce infestations below the economic threshold level.
Trap catches in the attract-and-kill (A&K) treatment plots during 2003 were not
significantly different than the twist-tie sections and resulted in trap shutdown. This was
not true in 2004 when traps in the A&K section caught 48% of the total GRB collected,
compared with only 13% in 2003. Why this occurred is unknown, but it is believed that
the producers of A&K failed to include the correct amount of pheromone in the 2004
batch, since there was no difference from the control. Studies are underway to determine
the amount of pheromone that was included in the A&K matrix.
I observed that the A&K drops often deteriorated quite rapidly under Florida
conditions. The protocol called for A&K to be reapplied every 6 weeks. However, I
noticed that many drops were almost dry after 3 weeks and totally missing during the 4th
through 6th week. In a few instances, I observed drops that lasted the entire 6-week
period. The drops that deteriorated within 3-4 weeks were generally more exposed to the
weather than the other drops. During the summer growing season, Florida vineyards
experience powerful storms with pelting rain, plus intense heat and solar radiation, and
these conditions may affect the stability and longevity of the A&K. Attract-and-kill
warrants further investigation to determine the frequency of application under Florida
conditions, and its overall effectiveness.
In 2003, there were no significant differences between the untreated (control) and
the Lorsban-treated sections. The Lorsban treatment was included in the study as a
standard chemical treatment for GRB control. Lorsban primarily controls first instar
larvae as they emerge from eggs and burrow to the roots. It can also reduce the number
of adults as they emerge from their cocoons. During 2004, traps in the vineyards treated
with Lorsban caught significantly fewer GRB than the untreated controls.
LastCall-GRB costs $100 per acre and it requires roughly one hour to treat an acre
and 3-4 applications per season. Depending on the size of the vineyard, this could be
rather labor-intensive. Future studies should evaluate how many drops per acre would
provide effective control. Instead of 900 drops per acre, perhaps the drops (1 drop = 0.05
g) could be consolidated into larger amounts and applied on fewer vines. For example,
1.5 g drops could be applied to 30 vines (= 45 g of A&K).
The results from the pheromone twist-tie treatments suggest a great degree of male
confusion and warrant further investigation as a GRB control tactic. A twist-tie
application rate of 254 units per acre is a large quantity and future studies should focus on
different deployment numbers. It may be important to compare the leopard moth
pheromone to the true GRB blend in further mating disruption studies. This was beyond
the scope of this study, but future studies should also incorporate the counting of pupal
skins as a means to determine GRB reductions from the treatments. Practically, 254
twist-ties per acre may be expensive for farmers ($116/ acre compared with $75/acre for
Lorsban). However, this initial investment may be offset by the premium prices charged
for organic grapes. A smaller deployment may be just as effective, as well as cost-
effective; for instance, 100 twist-ties per acre would cost $45. Mating disruption with
twist-ties is not a labor-intensive control strategy. It takes an average worker 75 minutes
per acre to deploy the twist-ties and the pheromones last the entire season of 150-180
days under average conditions.
Mating disruption with the use of the leopard moth (Zeuzerapyrina) pheromone
may be an effective, reduced-risk strategy for controlling grape root borer, and a good
alternative to conventional chemical control. It will need to be implemented for several
seasons concurrently to reduce moths to acceptable levels and then be implemented again
when populations surpass the economic threshold level (73 larvae per ha). It should be
incorporated into an IPM system that includes good weed management, and reduced
pesticide use. Attract-and-kill technology may also be an effective strategy for GRB
control, but more research is needed.
Table 5-1. Weekly mean number of grape root borers per trap for mating disruption,
attract-and-kill, Lorsban and untreated control treatments in four Florida
vineyards for 2003 and 2004.
Weekly mean trap capture SEM
0.00 + 0 c
1.07 .44 bc
3.07 .73 a
2.49 .62 ba
0.00 0 b
3.50 + .76 a
0.84 + .32 b
3.00 .75 a
Means in columns followed by the same letter are not significantly different (P = 0.05, Tukey's test)
SUMMARY AND CONCLUSIONS
The threat of grape root borer (GRB) Vitaceapolistiformis (Harris), (Lepidoptera:
Sesiidae) is often overlooked or ignored by Florida grape farmers. The damaging life
stage (larval stage) of the GRB occurs underground, and the adult goes unnoticed because
of its resemblance to the common paper wasp. Farmers often attribute reduced yields to
weather conditions or pathogens. The GRB is the most damaging insect pest of grapes
and has the potential to not only reduce yields, but to destroy the entire vineyard.
Presently, chlorpyrifos (Lorsban 4E) is the only chemical control listed for use of
GRB. Several studies have shown Lorsban to be ineffective for control of GRB (Wylie
and Johnson, 1978; Adlerz, 1984). Lorsban can only be applied once per season and is
effective for only 3-4 weeks in the soil, or less (in Florida) due to the volume and
intensity of Florida rainstorms. GRB flight periods last 3-5 12 months in Florida, so
Lorsban would be able to kill only a small part of the GRB population.
Two other control tactics have been recommended in other states: mounding and
use of landscape cloth. These tactics have shown promise in other states, however they
would be impractical in Florida for several reasons. For instance, the act of ridging
mounds under vines and then scraping them off can be destructive to roots, which grow
quickly into the mounded soil in Florida's climate. Landscape cloth would initially be
quite expensive and the cloth would be easily damaged by machinery in our sandy soils.
This study demonstrated the peak flight periods for GRB in 16 vineyards in 4
regions of Florida. Being able to determine peak flight will allow grape-growers to better
time their Lorsban application to coincide with the period of highest GRB emergence.
Lorsban can either be applied 35 day pre-harvest or post harvest. Bunch grapes ripen in
late June and July and peak GRB flight occurs in August and September. However, for
muscadine grapes, the period of highest GRB emergence and grape harvest coincide, and
Lorsban restrictions do not allow it to be applied during harvest. Consequently, this limits
the effect Lorsban can have on the majority of the population. Since Lorsban is most
effective on first instars, a period slightly later than peak emergence would be ideal. Also,
since eggs incubate for roughly two weeks, the best time to apply Lorsban would be two
weeks after peak GRB emergence. Therefore if grape growers insist on using Lorsban,
the best time will be after harvest. This is especially true for wine grapes, which are
harvested all at once. However, an earlier Lorsban application might be more effective
for farmers who run U-pick operations or sell grapes for the fresh-fruit market who often
harvest their grapes over an extended period, up to 8 weeks.
A component of my GRB research was to compare pheromone baited Universal
Moth Traps (Unitraps) with wing-style sticky traps. The results demonstrated that the
Unitraps caught significantly more GRB than the wing traps. Not only were they more
effective, but they are also easier to use and cheaper in the long run. Farmers should
continue to monitor for severity of GRB infestation. Current economic threshold levels
are based on pupal skin counts. New thresholds should be established using a more user-
friendly method of monitoring with Unitraps.
One result of monitoring for two years is that I was able to compare the total trap
catch of 2003 with 2004. The numbers of GRB decreased in 11 of the 17 vineyards and
for total trap catch in each region. Also, I began trapping in 2002 but was only able to
obtain data for late season emergence. This data for the same vineyards in 2003 showed
a reduction in total trap catch for the same periods of time. This information suggests a
trend and that mass-trapping may be a potential strategy for control of GRB. However,
further research is necessary to document this preliminary finding.
The purpose of the survey and analysis was to determine if there was a relationship
between cultural control practices, chemical usage, and environmental conditions with
total GRB trap catch. The results showed a strong correlation for 2003 and suggest that
GRB infestation may be predictable based on vineyard characteristics, farm management
practices, and environmental conditions. Certain factors, including weed control,
pesticide usage, and precipitation may favor the development of GRB. The data also
pointed out that certain cultural control techniques can be implemented in order to
disfavor the development of GRB and limit the potential infestation.
Mating disruption with pheromone twist-ties has been explored by a number of
researchers, all with promising results (Johnson and Mayes, 1980; Johnson et al., 1981;
Johnson et al., 1986; Johnson et al., 1991; Pearson and Meyer, 1996; Webb, 1991).
However, there is no commercial product available to farmers for use in mating
disruption of GRB. Several of the studies have compared the use of the current complete
blend with either the major or minor components (Johnson et al., 1991; Pearson and
Meyer, 1996). My study used an off-blend, the pheromone of the leopard moth Zeuzera
pyrina L. (Lepidoptera:Cossidae), which contains the same major component as the
GRB, to confuse the males of GRB. These treatments achieved complete trap shutdown
and did significantly better than the untreated control and Lorsban in 2003, and the
untreated control and attract-and-kill (A&K) in 2004, suggesting disruption of mating.
Trap shutdown does not prove disruption of mating, and further research is necessary,
that will correlate the effectiveness of the twist-ties with reduced pupal skin counts. If
successful, leopard moth twist-ties must be registered with the EPA for use in vineyards,
and produced commercially.
The attract-and-kill (A&K) treatments gave mixed results. In 2003 trap shutdown
was achieved and there were no differences with the twist-tie treatments. In 2004, A&K
was not significantly different from the untreated control. Based on the 2003 data, A&K
looks promising and warrants further investigation. No one tactic will be sufficient in
controlling GRB. Wild grapes occur quite extensively in Florida, and GRB will always
be immigrating into vineyards from forested areas. An integrated pest management
program is necessary to control GRB in Florida vineyards. This includes good weed
management, good site selection, reduction in chemical usage, as well as the adoption of
reduced-risk pesticides. Farmers need to monitor GRB populations and implement
control strategies under epidemic population densities. These strategies may include the
use of Last Call-GRB (A&K), Lorsban, and the use of pheromone twist-ties for mating
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Scott Weihman was born in Rockford, IL, on May 13, 1967. He began his
academic career in 1985, studying marine biology at the University of the Virgin Islands.
Later, he transferred to Hawaii and earned his BA in environmental studies from the
University of Hawaii in May of 1992. Shortly thereafter, he joined the Peace Corps to
teach sustainable agriculture to farmers in a remote region near the Panama Canal. Scott
has 13 years of horticulture experience and had a successful landscape design business in