f/t ., 5" BIG BEND HORTICULTURAL LABORATORY
Big Bend Hort. Lab. Mimeo Report BBL 67-5 March 10, 1967
OBSERVATION AND CONTROL EXPERIMENTS CONCERNING PEACH TREE
BORER AND LESSER PEACH TREE BORER IN NORTH FLORIDA.
John Van Duyn, Research Associate in Entomology1
The peach tree borer, Sanninoidea exitiosa (Say) and the lesser peach tree
borer Synanthedon pictipes (Grote and Robinson) are two of the more important pests
of peach, Prunus persica east of the Rocky Mountains. Both peach borers are an
important factor in determining the success or failure of commercial peach ventures.
From May 1966 to December 1966 observations and experiments were conducted
concerning S. exitiosa and S. pictipes. All observations were conducted in Jeffer-
son and Madison counties, Florida and experimental plots were located in Jefferson
county, Florida. This paper reports on the biology of both insects and insectic-ido
tests concerning control. Each insect will be discussed separately.
REVIEW OF LITERATURE
Peach Tree Borer Sanninoidea exitiosa (Say) was first described by Say in
1823 and named Aegeria exitiosa. A previous name of Zygaena persicae was given by
Barton in 1805, but no description has been found. The scientific name was changed
eight times before Beutermuller erected the new genus Sanninoidea using exitiosa
(Say) as the species name in 1896.
The peach tree borer overwinters as a larva under the bark of host trees and
begins activity in the spring when the temperature reaches an adequate level.
Peterson (1923) reports that in New Jersey activity and feeding begins when soil
temperatures reach 50 degrees F. or higher and a few larva do not become active
until average soil temperatures reach 60 degrees F.
Pupation may occur early in the spring for some overwintering larva are in the
last instar before hibernating. Pupation is proceeded by the spinning of a dirt,
silk, frass and gum cocoon. An average of 1 day, but as long as 4 days is required
for cocoon construction according to Becker (1918). The upper end of the cocoon
is loosely constructed to allow the pupa to break through when the adult is ready
to emerge (Snapp, 1932).
Becker (1918) reported adult emergence to be in 4 stages which are as follows:
1. A tear forms across the top of the cocoon. Pupa in such cocoons are likely
to emerge that day.
2. The tear across the cocoon widens and the pupa will push approximately
1/3 of the way out. About 20 minutes rest follows.
1Prepare: ih cooperation with Dr. Milledge Murphey, Entomologist, Department of
Entomology, University of Florida, Gainesville.
200 cc 3/10/67
3. With circular, twisting movements the pupa will push itself about 2/3 the
way out of the cocoon. Often pupa will twist completely out of the cocoon in which
case emergence from the pupal skin seems difficult.
4. After a short rest period the adult begins moving forward within the pupal
case. With pressure being applied above the thorax the pupal skin splits. The
top of the thorax pushes out of the pupal case, followed by the head, antenna,
prothoracic legs and finally the whole insect wiggles out.
Say (1823) described the adults as being clear winged moths with the female
slightly larger than the male. The female is very dark steel blue with the except-
ion of the fifth abdominal segment which is bright orange and the metathoracic
wings which have a hyline spot. The male is also steel blue, but not as dark as
the female. Males have several (usually 5) narrow pale yellow abdominal stripes
and the head, thorax and legs may have patches or stripes of yellow setae. Both
mesothoracic and metathoracic wings have a hyline spot.
Unlike the majority of moths peach tree borer adults are active during the
day. Adults do not feed other than taking up small amounts of water and are not
attracted to sugar water or other chemicals simulating nectar (Peterson, 1923).
Soon after emergence the adult female is ready to mate. Males are attracted
to females by a sex attractant and copulation takes place, usually lasting from
45 to 90 minutes as reported by Peterson (1923). Cory (1913) reports that the time
between fertilization and oviposition varies from a few minutes to over 24 hours.
Each egg is played singly and is glued in place by a secretion deposited before and
during egg delivery. Under caged conditions Becker (1918) observed an average of
522 eggs per female whereas Cory (1913) observed 161 to be the maximum number de-
posited by a single female. Peterson (1923) reported an average of 314.5 eggs per
female and 1072 as maximum from a single female. Incubation takes approximately
13 days under warm summer conditions.
Peterson (1923) states that under orchard conditions most eggs hatch during
the night or early morning. Larva exhibit a positive geotropic tendency and prefer
to enter the tree slightly below the ground level (Snapp and Thomas, 1943). Larva
of many sizes may be found in a single tree due to the long egg laying period.
Snapp (1958) reports that adults have been observed as early as April 25 and eggs
in the orchard have been known to hatch as late as December 7 in the Fort Valley,
Georgia region. Larva feed throughout the warm months of the year and emerge when
weather conditions permit. Most areas report one generation a year with the ex-
ception of middle Georgia. Snapp and Thompson (1943) report an average of one and
a partial second generation, but in favorable years two generations may develop
in the Fort Valley, Georgia area.
Lesser Peach Tree Borer The original description of the lesser peach tree
borer was given by Grote and Robinson in 1868 and named Aegeria pictipes. In 1881
Henry Edwards redescribed the insect naming it Aegeria invsitata. Beuternmuller
fixed invsitata as a synonym for pictipes in 1893. Smith in 1890 placed the insect
in the genus Sesia which was later transferred to the genus Synanthedon by Holland
(1903). Synanthedon pictipes (Grote and Robinson) is the present scientific name ;
and is commonly known as the lesser peach tree borer or plum tree borer.
Winter is passed in various stages of larval development under the bark and
in tunnels of host trees. From observations made at Gypsum, Ohio in late November,
King (1917) reported many larva hibernating in deep crevices of their burrows while
others constructed loose silk and frass cells. Larval activity resumes in the
spring in northern latitudes while in the southern states larva may feed on warm
Pupation begins soon after temperatures reach an adequate level. Bobb (1959)
reports that many larva pupate with the approach of warm weather without further
feeding. Pupation may take place in early March in latitudes of Virginia (Bobb,
1959) and eastern Texas (King and Morris, 1959), but is delayed until early or mid
April in latitudes of New York (Smith, 1951), Ohio (King, 1917) and South Dakota
Cocoons are constructed within the burrows close to the wound's edge and are
concealed behind a disk which covers the burrow entrance (King, 1917). The larva
remain within the cocoon from 3 to 6 days before transforming into a pupa (Gilbert-
son, 1934). According to Gilbertson (1934) adult emergence is as follows: The
pupa becomes swollen and active before emergence. Aided by abdominal and anal
spines the pupa wiggles to the anterior of the cocoon. The cocoon wall is cut by
means of a sclerotized structure on the pupa head and forward motion continues until
the pupa projects 1/2 to 2/3 of itself into the open air. A short rest period fol-
lows after which the enclosed moth applies pressure above the thorax and splits the
pupal case. Upon emergence the moth remains inactive for 30 to 40 minutes while
its wings expand and dry.
Mating occurs about an hour after the female emerges and in most cases before
flight (King, 1917). Males are attracted by a sex attractant emitted from glands
on the ovipositor and appear within a few minutes in areas where the insect is
abundant (Bobb, 1956). Males fly over the female striking until union is achieved.
Claspus which are lined with hooks aid the male in holding the female. Copulation
usually lasts from 45 to 60 minutes (King, 1917).
Oviposition occurs soon after mating and females usually confine egg laying to
bright warm days (Girault, 1907). Eggs are deposited 2 to 4 at a time, but may be
played in patches, especially around wounds which seem to stimulate egg laying
(King, 1917). Incubation takes from 7 1/2 to 8 1/2 days under warm conditions
(Girault, 1907) (King, 1917).
Larva begin feeding on cambium and inner bark layers soon after hatching.
Larva from eggs laid in early spring may reach the sixth instar by fall in northern
New York (Smith, 1951) and South Dakota (Gilbertson, 1934) by late summer in Ohio
(King, 1907)carid mid summer in Virginia (Bobb, 1959), Texas (King and Morris, 1956)
and Georgia (Girault, 1907). Thus there is one complete generation in northern
latitudes and two generations in southern latitudes.
Adults of the lesser peach tree borer are dark steel blue with yellow markings
on the thorax, legs and abdomen. Both mesothoracic and metathoracic wings have a
hyline spot. Sex can be determined on the basis of makes having lateral setae on
the antenna and one caudal tuft of setae whereas the female's antennal setae lie
against the segments and the caudal tuft has three sections (King, 1917). Adults
are most active on bright sunny mornings and appear much like wasp when in flight
MATERIALS AND METHODS
Observations Observations were confined to viewing general habits and ex-
tent of damage. No particular schedule was followed nor was there any intense
study of the life history.
A study of the burrowing habits of both insects was made. Area and side of
the tree, length and depth of burrows and miscellaneous characteristics were con-
sidered. Measuring burrow lengths was accomplished by cutting the bark away and
measuring or running a wire into the burrow. Length of larva was also measured.
Lesser peach tree borer emergence was noted from infested trees which initially
had all old pupa cases brushed away. New pupa cases were counted to determine the
number of moths emerged, and all pupa cases were brushed away after each count.
Sixth instar peach tree borer larva which were beginning to construct cocoons
were collected and held to determine the days required to complete the pupa stage.
Records were begun when cocoon construction was complete and ended when moths
Daily maximum and minimum temperature for air and soil at 4 inch depth were
taken at the Big Bend Horticultural Laboratory weather station. Also, old weather
records were furnished by the station.
Control Experimental plots were located at the Big Bend Horticultural Lab-
oratory orchard at Monticello, Florida and in a commercial orchard at Waukeenah,
Florida. The randomized block design was employed with 3 replications and 7 treat-
ments. Each treatment contained 4 trees.
The Big Bend Horticultural plot contained 3 consecutive rows each composing
one block. All trees were 2 year old Maygold peach trees with trunk diameters
ranging from 4 to 5 inches.
At Waukeenah, all three blocks were arranged in a single row which was the
second fow from the bordering woods. The plot was placed near the orchard's edge
in hopes of having a greater number of borers. All treatments were applied to
3 year old Maygold peach trees with trunk diameters from 6 to 8 inches.
Commercial spray programs had been employed at both orchards prior to the be-
ginning of the experiments. At least three weeks time had elapsed from the date of
the last applied commercial spray until the first experimental treatment.
Sprays were applied with a John Bean #200 peach sprayer using the hand gun at
300 p.s.i. Each tree was sprayed thoroughly giving emphasis to the large limbs,
crotch and trunk down to the soil. Sprays were mixed in 25 gallon amounts to save
material. After each treatment the tank was rinsed out thoroughly to avoid mixing
chemicals. Chemicals, rates and number of applications used are given in Tables
I and II.
RESULTS AND DISCUSSION
Observations of Peach Tree Borer In North Florida peach tree borer passes
the winter as a larva and emerges when weather permits. The author feels that in
North Florida activity of all stages is interrupted only by cold spells rather than
the entire cold season. Indeed, if S. exitiosa larva in North Florida is active at
temperatures given by Peterson (1923) in New Jersey (above 50 degrees F.) there is
not a single month in an average year in which larva are totally inactive. In ad-
dition to air and soil temperatures being relatively high, trunk temperatures on .*
bright sunny days range considerably higher than air or soil temperatures. Table
III gives average soil and air temperatures for winters 1964-65 and 1965-66.
Adults have been observed as early as mid March and it is felt that feeding, pupat-
ion and emergence may occur any time when temperatures are adequate.
Observations indicate that adults confine egg laying on the tree trunk from
ground level to approximately 6 inches above the soil. Trees previously infested,
injured or having rough bark are preferred for oviposition.
Larva burrow from approximately 2 inches above the soil to 3 inches below the
soil and sometimes burrow along large surface roots. Burrows are more often verti-
cal than horizontal and average 3 inches in length, but may be as long as 7 or 8
inches. Burrows are generally irregular so accurate average length is difficult to
determine. Larva show no preference as to which side of the trunk is burrowed. On
trees heavily infested most burrows unite and one large common burrow is formed
with larva feeding along the edges. Burrows are usually filled with large amounts
of frass and gum. During periods of wet weather gum will freely exude from the
wound and often covers the ground around the trunk. If a tree is heavily infested
it soon becomes girdled and dies. Most infestations examined contained only 1 or
2 larva, but as many as 7 large and 14 small larva were removed from one wound.
Larva found in the same infestation may vary considerably in length because
egg laying lasts many months. Lengths may range from 1/8 inch for newly hatched
larva to 1 1/2 inches for sixth instar larva. Coloration of the larva is most
commonly milky white, but may be tinted brownish if feeding on dark colored matter.
The larva's legs are not adapted for walking and are little more than small hooks.
The head is heavily scleritized as are plates on the first and last segments of
Cocoons are constructed in the burrow, against the trunk and in the soil next
to the tree. Those cocoons constructed in the soil contain much soil and debris
while those constructed in or on the tree are primarily made of gum and frass. The
majority of the cocoons observed by the author were in the burrows of the tree or
on the outside of the wound. The average length of the pupal stage was 16 days for
5 pupa collected in August. This figure includes time spent in the cocoon by the
larva before it pupated.
Peak emergence took place from mid July until the last of October. Maximum
emergence during this period was in September. Emergence seems to be retarded by
cloudy or rainy weather.
Adults mate soon after emergence and seemingly before they fly. Only three
emergences were observed in the field and all mated within a half hour before they
The female lays her eggs by touching the abodomen to the selected site while in
In North Florida there appears to be two and a partial third generation yearly.
Years which have mild short winters may have three complete generations.
Peach tree borer has been observed infesting Prunus persica, peach and nectarine
and P. serotina, Wild Cherry.
Observations of Lesser Peach Tree Borer The lesser peach tree borer causes
damage similar to that of peach tree borer, but confines its infestations to the
upper trunk, crotch and limbs. Also in appearance lesser peach tree borer closely
resembles the male peach tree borer, but has only 2 abdominal stripes whereas peach
tree borer males have 5 abdominal stripes.
Lesser peach tree borer passes the winter as a larva or pupa and pupate or eme-
rge when temperatures reach an adequate level. In most years uninterrupted activity
probably begins in March. Again the author feels that emergence is sporadic through-
out the winter months and more so than the peach tree borer because of its habitat
and shorter life cycle.
Larva of the lesser peach tree borer closely resembles peach tree borer larva,
but is slightly smaller. Length ranges from 1/8 inch for newly hatched larva to
1 1/4 inches for sixth instar larva,
Burrows are irregular and are generally directed laterally along the limb.
Length of burrows is difficult to determine because burrows are very irregular.
Estimated average length of burrows is approximately 3 inches if elongate and 1 1/2
to 2 inches across if circular shaped. Often many larva may be found in a common
burrow in which case larva work outward from the center of the wound. In late sum-
mer larva, pupa and cocoons may be found in a single wound. It is not uncommon to
find as many as 25 larva in a single wound. Larva may be found in limbs as small
as 1/2 inch in diameter to the largest limbs or trunk. When in small limbs larva
tunnel down the middle whereas in large limbs they mainly remain just under the
Cocoons are made with gum and frass and are usually found in old burrows close
to the entrance. Peak activity periods in 1966 were from May until October with
the highest emergence in August and September. Heavily infested trees may have
numerous pupal cases projecting from old wounds in the late summer. 134 pupal cases
were counted in August from one large tree which had been damaged by machinery.
There appears to be three full generations per year and possibly a partial fourth
Adult lesser peach tree borer are strongly attracted to previously infested
areas or any type of wound. In heavily infested wounds most larva can be classified
into several size groups. Each group appearing to have come from one female or
several females ovipositing approximately at the same time. Seldom are numbers of
the same size larva found except in old wounds indicating that wounds stimulate the
female to lay an increased number of eggs.
Lesser peach tree borer has been observed attacking Prunus persica, peach and
nectarine, P. serotinia, wild cherry and P. augustifolia, wild plum.
Damage The extent of damage in North Florida varies considerably from
orchard to orchard. Orchards which have extensive machinery damage generally have
heavy borer damage. Orchards given intensive care often show as.much or more borer
damage than orchards given mediocre care because of machinery damage. Infestations
of either species left unchecked enhances the problem by increasing the field po-
pulation in the vicinity and borers are attracted to old wounds. If wounds are
continually attacked eventually the trunk or limb is completely girdled.
In collaborating with entomologists working with peaches in the Southeast the
author has noted a growing concern with lesser peach tree borer. In the past peach
tree borer was the more important pest while lesser peach tree borer caused less
damage. Most growers carried on active spray programs against peach tree borer,
but considered lesser peach tree borer incidental. Many research workers dealing
with these insects believe that peach tree borer has become less abundant due to
chemical treatment and is not as important as it once was. Concurrently lesser
peach tree borer has become more tolerant to chemicals and is more numerous today
because spray programs were not directly aimed at the insect and its life cycle is
relatively short. Also, with sprays concentrated around the trunk for peach tree
borer control and in the canopy for plum curculio Conotrachelus nenuphar (Herbst)
control of lesser peach tree borer has most frequently infested the crotch which is
more damaging than limb infestations. At present time lesser peach tree borer is
considered more important than peach tree borer in the Southeast as well as North
Control Practices and Results of Control Experiments Control programs con-
cern cultural practices and chemical control. Peach tree borer control relies
mainly on the use of an effective insecticide applied two or three times from July
to October. Insecticides are applied to the lower two feet of the trunk and the
soil within one foot of the trunk. Also, avoiding machinery damage to the base of
the tree helps prevent peach tree borer infestation.
Cultural practices play an important part of lesser peach tree borer control.
The most common points of attack are infested wounds, bad pruning stubs, large prun-
ing scars, sharp angled crotches, split crotches and broken or scraped limbs.
These favored areas may be eliminated by proper pruning practices and avoiding in-
jury to trees. Chemical treatment for lesser peach tree borer is the same as for
peach tree borer, but sprays are directed to the crotch and scaffold limbs.
The experimental plot at the Big Bend Laboratory was abandoned because of lack
of insects in all treatments including the checks. The Waukeenah plot had few
peach tree borers and a moderate number of lesser peach tree borers. The results
(Table IV) for reduction of peach tree borers is not representative due to lack of
insects in the checks. However, it is felt that lesser peach tree borer results
Three applications of .36% dieldrin and two applications of .09% thiodan
endosulfann) reduced lesser borer 97.1% as compared with the check. The only other
treatment considered effective was two applications of .24% dieldrin which gave
94.8% reduction of lesser peach tree borer over the check.
Chemicals, rates and application dates of insecticide experiments,
Big Bend Horticultural Laboratory Plot
Material Rate per 100 gals. Application Dates
3 lbs. actual
3 lbs. actual
1.5 lbs. actual
0.3 lbs. actual
0.3 Ibs. actual
Chemicals, rates and application dates of insecticide experiments
at Waukeenah, Florida.
Material Rate per 100 gals. Application Dates
3 lbs. actual
2 lbs. actual
0.75 lbs. actual
1.5 Ibs. actual
0.3 Ibs. actual
0.3 lbs. actual
Air and Soil temperatures for winters of 1964-65 and 1965-66.
4" Soil Temperature
Max. Min. Mean
Results of the field control experiment at
Chemical and Dates Mean No. of borers Percent reduction
rate per 100 gal. applied per tree over check
Peach tree Lesser Peach tree Lesser
borer borer borer borer
3 lbs. actual 8/20 .166 .333 81.9* 97.1
2 Ibs. actual 8/31 .666 .583 27.3 94.8
.75 lbs. actual 8/31 .120 .333 91.5 97.1
Ortho 9006 6/29
1.5 Ibs. actual 8/31 .830 9.830 9.1 12.0
0.3 lbs. actual 8/20 ,666 2.830 27.3 74.7
0.3 lbs. actual 7/30 .830 4.250 9.1 62.0
Check .916 11.666
'Figures for reduction of peach tree borer are not accurately representative
because of the low number of these insects in the check trees.
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