INSTITUTE OF FOOD AND
UNIVERSITY OF FLORIDA
A Vegetable Crops Extension Publication
Vegelablc Crops Depalrment 1255 HSPP GCanc\v'illc. FL
32611 Telephone 392-2134
May 15, 1990
I. NOTES OF INTEREST
B. Vegetable Field Day
II. COMMERCIAL VEGETABLES
A. Geminivirus Subcommittee (GVS) II
B. Crop Pollination Pointers
C. Pumpkin Production for the Fall Holidays
D. Maintaining Air Quality in Cold Storage Rooms -
Part 1 Concerns and Symptoms
III. PESTICIDE UPDATE
.I A. Poast (Sethoxydim) Label for Annual Grass Control in
SDry Beans, Succulent Beans, Dry Peas, Succulent Peas.
Kski. B. Knowing Herbicides Used Previous Year.
". IV. VEGETABLE GARDENING
SA. Tomato Leaf Roll
.., Note: Anyone is free to use the information in this newsletter.
Whenever possible, please give credit to the authors. The purpose of
trade names in this publication is solely for the purpose of providing
Si information and does not necessarily constitute a recommendation of
S,^. ^- the product.
The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research,
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I. NOTES OF INTEREST
II. COMMERCIAL VEGETABLES
Saturday, June 9, 1990. Live Oak
Vegetable and Fruit Crops Field Day,
8:30 AM 12:00 Noon, Live Oak AREC.
(Contact Bob or George Hochmuth or Tim
June 9, 1990. Urban Gardening
Harvest Fair. 10:00 AM 2:00 PM.
Duval County Extension office,
Jacksonville. (Contact Jim Stephens).
June 11-15, 1990. 4-H
Horticulture Institute, Camp Ocala.
(Contact Bob Black, Environmental
July 9 August 25, 1990.
Vegetable Crop Production and Marketing.
International USDA Technical Course TC
130-11. (Contact Steve Sargent).
B. Vegetable Field Day.
A mini-field day will be conducted
at the North Florida Research and
Education Center, Quincy on Tuesday,
June 12, 1990. Registration for program
will start at 12:45 p.m. Dr. Phillip Dukes,
Research Pathologist with the USDA
Vegetable Breeding Laboratory,
Charleston, S.C. will be speaking on new
southern pea and sweet potato varieties
that have been released from the USDA
program at Charleston. The program will
also include a seedless watermelon trial
(30 varieties), a standard watermelon trial
(20 varieties) and a tomato variety trial,
Also of interest will be an insecticide
screening trial for thrips and a tomato
spotted wilt virus mapping study.
Interested persons can contact
Stephen Olson at NFREC Quincy at
904/627-9236 for more information.
Over thirty scientists representing
IFAS statewide, the USDA, DPI, and
private enterprise assembled in Bradenton
on May 2 for the second meeting of the
GVS (Vegetarian 90-03). The following is
a brief account of what transpired.
Subcommittee coordinator, Dr.
George Agrios, first asked the group to
report on the present situation. The
group agreed that generally whitefly
populations have been low this spring
(probably due to the Christmas freeze)
and subsequently the incidence of
geminivirus has been low also. Dr.
Charles Melinger (Glades Crop Care)
mentioned that the geminivirus found in
Homestead was attributed to virus
reservoirs that survived the freeze. He
added that whitefly populations are
presently increasing statewide and that
geminivirus will certainly be with us again
Dr. Jim Price (Bradenton)
commented that whiteflies imported on
poinsettia cuttings from California may
add new germplasm to our whitefly bank.
Dr. Phil Stansly (Immokalee) indicated
that the economics of the tomato market
may lead to early abandonment of tomato
fields. This practice will result in severe
geminivirus incidence this fall if the
plants are not quickly and properly
Dr. Ernest Hiebert (Gainesville)
has not identified geminivirus in weed
samples sent to him for testing with the
DNA probe, so an alternate host for the
virus still eludes researchers. However,
he has found that one of the viruses in
our complex can be mechanically
transmitted to Nicotiana edwardsonii (a
tobacco species). This should facilitate
separation of the complex.
The discussion then turned to
ongoing work and future plans. Dr. Jay
Scott (Bradenton) has begun screening for
tomato resistance to the geminivirus(es).
Drs. Gary Simone and Bob McGovern
(Immokalee) will begin a statewide survey
of tomato virus incidence and dynamics.
Dr. Schuster (Bradenton) has been
working with eggplant and okra as
whitefly trap crops, and with Dr. Jim
Kring (Bradenton) will continue work with
colored mulches particularly yellow which
attracts the whitefly, but it's surface
temperature can kill the fly.
University personnel have
submitted grant proposals to the federal
government, the state legislature, and
BARD (Bilateral Agricultural and
Development program with Israel) to ask
for funding to assist in research on
geminivirus problems in vegetables. The
USDA has been encouraging commodity
groups to lobby the federal legislature for
The GVS further adopted the
Tomato Spotted Wilt Virus (TSWV) as a
committee project. Melinger said that
TSWV has been present in north Florida
since 1986 causing vegetable crop losses of
between 0.5 5% annually, but has not
moved deeper into Florida. Dr. Joe
Funderburk (Quincy) has been working
with thrips and TSWV for several years
(see Vegetarian 90-04) and appears to be
a good source of information. Dr. Tom
Kucharek (Gainesville) has begun a survey
of the incidence and dynamics of TSWV
and will be working in cooperation with
Alabama and Georgia to produce a fact
sheet on TSWV. A southern region
information exchange group is forming to
address TSWV and geminivirus. Jay Scott
indicated that Peto Seed Co. in
cooperation with the University of Hawaii
has developed TSWV resistant breeding
lines in tomato and this material may be
forthcoming more rapidly than
geminivirus resistant material.
(Vavrina, Vegetarian 90-05)
B. Crop Pollination Pointers.
Vegetables require large amounts
of pollen to result in optimum seed set
and fruit size and shape. The pollen is
produced in the male organs of the
flowers, the anthers and transferred to a
part of the female organ, the stigma.
Pollen grains "germinate" and a pollen
tube helps deposit the male gametes in
the ovary where they can fertilize the
female gametes. Fertilization results in
seed development and stimulates the fruit
(ovary) to develop.
For some vegetables, snap beans,
peppers, and tomatoes, these processes of
pollination and fertilization take place in
the same flower because both male and
female organs are present in the same
flower. Vibration action, (caused by wind)
serves to move the pollen from the
anthers to the stigma.
Other vegetables, such as sweet
corn, squash, watermelon, cucumbers, and
muskmelons have the male and female
organs separated in different flowers,
usually on the same plant. This
separation of sexual organs requires that
some agent (pollen vector) move the
pollen from the male flower to the female
flower. For corn, wind is the vector.
Insects function as the vector for the
other cucurbit crops and honey bees are
the most efficient of these vectors.
Fruit set, shape, and size in these
cucurbit crops depends on efficient bee
activity in the field. Often this means
moving bee hives into the field to ensure
adequate pollination. The following are a
few pointers to help get the most out of
an investment in honey bee hives.
1. Secure an adequate amount of
hives. Cucurbit crops require about 10
bee visits to each flower to ensure
adequate pollination. Each seed in a
melon or cucumber comes from a separate
pollination. Since the shape and size of
these fruits is related to the number of
properly developed seeds, one can see
that the amount of pollen delivered to a
female flower is important.
Depending on source of
information, the number of bee hives
needed to achieve these high numbers of
flower visits will differ. This is because
size and population of hives will vary from
supplier to supplier. In addition, there is
a good possibility that no one really
knows for sure how many hives are
required. Probably a better rule-of-thumb
would be to base the number of hives on
the number of flowers present in a field.
Recommendations from some sources call
for one bee for every 100 flowers in the
field. Under this system, the number of
hives could be increased as the availability
of pollen and nectar increase. Honey bees
do not pollinate for fun (maybe they do)
but the pollination results from the bee's
activities in gathering food (pollen and
If a muskmelon crop had about
4000 plants per acre and the number of
flowers varied from 5 per plant early in
the season to 80 later, then the minimum
number of bees needed would range from
200 to 3200. In most situations, these
requirements could be more than handled
by one hive of 30,000 bees per acre. One
hive per two acres should more than
adequately fill the need for pollination of
cucurbit crops. This assumes that a large
proportion of this hive is available for
pollination and that there are not other
more attractive flowers in the vicinity.
2. Care of the bees. Bees hired
for pollination should be placed where the
hives do not receive direct sun light all
day. Along field edges or under scattered
trees would be good. Growers should be
sure that water is available nearby.
Sometimes it would be a good idea to
place troughs of water nearby. Place
some type of floating object in the trough
for bees to drink from.
Growers need to remember that
pesticides used for insect control in the
field may be also deadly to bees. It is
extremely important to schedule
insecticide applications when bees are not
active in the field. For melons, the
flowers remain open from sun-up to sun-
down. Therefore insecticide applications
must be scheduled outside of the daylight
hours. Some insecticides highly toxic to
bees are listed below. Some of these
chemicals might be toxic to bees even one
day after chemical application. Growers
need to check the bee toxicity level of the
insecticide to be used on a crop.
SOME INSECTICIDES HIGHLY TOXIC
3. Pollination contract. It is a
good idea to use a written agreement
between the grower and bee supplier.
This agreement should spell out what
each party is responsible for. Some items
to include in the contract are:
1. Names of parties and date of
2. Length of term of the agreement.
3. Number and size of hives to be
delivered. Condition of the hives.
4. Date of delivery and removal.
5. Responsibilities of the bee supplier
in caring for the hives (inspection,
supering, honey removal, etc.).
6. Responsibilities of the grower.
(Permit access to hives by
beekeeper, insecticide use, water,
etc.). Grower and beekeeper
should review insecticide programs
7. Financial arrangements.
8. Arbitration arrangements in case
Use of honeybees for crop
pollination is a sound grower practice and
it can help secure high yields of high
quality fruits. Lack of bees could be one
explanation for a grower's poor fruit set
at certain periods of the early season.
Use of bees however requires planning
and care so that neither the beekeeper
nor the grower gets stung by an
unfortunate circumstance. Hopefully
some of the above pointers will help.
(Hochmuth, Vegetarian 90-05)
Pumpkin Production for the
Pumpkins are popular in the fall
months for Halloween jack-o-lanterns and
for decorative purposes through
Thanksgiving. Florida does not produce
enough pumpkins to satisfy internal
demand so pumpkins are shipped into the
state, primarily from the Midwest.
Pumpkin production has not been
extensive in Florida because of very high
disease pressure and insect populations in
summer and early fall. However,
improved fungicides have been developed
for downy mildew and powdery mildew
that provide excellent control with good
and timely spray coverage. Insecticidal
control of pickleworm and virus-vectoring
aphids is also essential.
Pumpkins can be established by
direct field seeding or with transplants in
early to mid July, respectively. This
schedule has consistently produced
pumpkins for Halloween in Manatee
County. Some adjustments in planting
time may be necessary for other parts of
the state or to allow for a longer
Production on raised beds on 10 to
15 ft. centers provides drainage and space
for extensive vine growth. In-row spacing
of 2.5 ft. for miniature pumpkins and 5 ft.
for other types should provide adequate
space for growth.
Second-crop plantings on mulched
beds following tomatoes or peppers
provides some economics in production
costs and is widely practical. Additional
fertilizer, where needed, can be applied
using the fertilizer injector wheel. The
total nitrogen (N) crop nutrient
requirement (CNR) of 120 lbs./acre can
be injected in two or three applications.
Potassium (K) requirements will be one-
half to three-fourths of the CNR as
determined by the original soil test; the
remainder coming from residual K
Residual phosphorus (P) and
micronutrients in the bed should be
sufficient for the pumpkin crop.
For new plantings on mulched
beds, 120 lb. N and P and K as
determined from the soil test should be
applied preplant. On unmulched beds,
the P and micronutrients should be
incorporated in the bed and the N and K
applied in 40 lb. increments at planting
and in two sidedressings before the vines
cover the bed.
Pumpkin varieties should be
selected based on established or
anticipated demands. The varieties listed
below by fruit size have performed well in
central Florida trials.
Giant 25 to 80 lbs.
Big Max open pollinated
Big Moon open pollinated (PVP)
Large 10 to 30 lbs.
Connecticut Field open pollinated
Howden open pollinated (PVP)
Medium 5 to 10 lbs.
Autumn Gold hybrid
Young's Beauty open pollinated
Small 1 to 5 lbs.
Baby Pam open pollinated
Little Lantern open pollinated
Miniature < 1 lb.
Munchkin open pollinated
Jack-Be-Little open pollinated
Sweetie Pie open pollinated
Growers are advised that
production of pumpkins in the summer
and early fall requires stringent pest
management practices, especially for foliar
diseases. As with other vegetable crops,
a market should be established before
(Maynard, Vegetarian 90-05)
D. Maintaining Air Quality in
Cold Storage Rooms-Part 1-Concerns and
Management and supervisory
personnel are continually concerned with
providing a safe environment for their
workers. Precautions must be taken to
ensure that the air in cold storage rooms
remains free from buildup of noxious
gasses and contains sufficient oxygen. We
have received reports of isolated instances
in which workers have experienced
headaches and dizziness after entering
these areas. There are several potential
causes for these symptoms.
Propane-powered forklifts are used
in the majority of packinghouse
operations. The engines combust fuel and
oxygen to produce carbon dioxide,
hydrocarbons (including ethylene) and, in
the case of a poorly-tuned engine, carbon
monoxide. In most packinghouse
operations, forklifts are continually
entering and exiting the cold rooms as
pallets are loaded and unloaded. This
constant movement generally provides
adequate opportunity for fresh air to
exchange with the air in the refrigerated
area. However, if forklifts are operated
for any length of time within the confined
area of a cold room there is the
possibility of accumulation of the exhaust
gasses which might lead to the above
symptoms in the employees working in
that area. Symptoms of asphyxia are
noticeable when the oxygen level drops
from 21% in fresh air to 16%. Also, any
accumulated levels of ethylene (as little as
1 part per million) can cause enhanced
senescence and overall decrease in the
shipping life of the stored crop.
Symptoms of ethylene exposure include
acceleration of ripening of fruits and loss
of green color in leafy crops, as well as
the development of russeting in lettuce
and bitterness in carrots.
Crops continue to respire after
harvest, taking up oxygen and giving off
carbon dioxide. Ethylene is also given off,
the rate dependent upon the crop.
Respiration can occur at high rates for
crops such as sweet corn, mushrooms,
okra, peas, spinach and broccoli. For
cases in which a well-sealed cold room is
fully loaded with a high respiring crop
and closed during off-peak hours, it is
conceivable that the oxygen level in the
room could be lowered enough to cause
dizziness if entered prior to adequate
ventilation. Precooling crops to
recommended storage temperatures
Chlorine is an effective general
disinfectant for dump tanks, hydrocoolers
and cleaning packing line components and
bulk bins. Care should be exercised to
avoid prolonged contact with chlorine,
since it can volatilize into gas. According
to one safety data sheet, chlorine is
detectable at 0.3 ppm and becomes
intolerable at 2.6 to 41 ppm, depending
upon the individual. The OSHA
permissible exposure limit (PEL) is 1 ppm
average exposure during an 8-hour period.
Exposure limits of 3 ppm for 15 minutes
are recommended. Symptoms of
overexposure include severe irritation to
eyes, nose and respiratory tract.
Exposure to 35 to 51 ppm for one hour or
a few breaths at 1000 ppm can be lethal.
Ammonia refrigerant systems
should be routinely checked for leaks,
since ammonia gas is also quite toxic. In
the case of an ammonia leak, the gas can
accumulate in the cold room or adjacent
area. It has symptoms similar to chlorine
gas but has a higher OSHA PEL of 50
ppm average during an 8-hour period.
The maintenance of air quality in
and around packinghouse storage facilities
is essential to the well-being of workers
and produce. Next month means for
avoiding build-up of contaminated air and
procedures for removal in the case of an
accident will be discussed.
(S. Sargent, Vegetarian 90-05 Special
thanks to D. Endicott, Industrial
Hygienist, Environmental Health and
Safety Division, University of Florida, for
reviewing this article.)
III. PESTICIDE UPDATE
A. Poast (Sethoxydim) Label
for Annual Grass Control in Dry Beans,
Succulent Beans, Dry Peas, Succulent
The herbicide Poast has obtained a
label for the control of certain annual
grass species in beans and peas. The
rates for control of weed species range
from 1/2 pint to 2 pints material + 2
pints crop oil concentrate per acre
depending on the species. For most grass
weeds in Florida a rate of 1 pint Poast
(0.1875 lb a.i.) plus 2 pints of a crop oil
concentrate is recommended.
Poast may be used on beans
including the Phaseolus genus adzukii
bean, field bean, kidney bean, lima bean,
navy bean, pinto bean, mung bean etc.);
Lupinus sp. (sweet lupine, white lupine);
cowpeas Vina species (includes
southern peas, black-eyed pea, broad
bean); and other species including fava
bean, chick pea (garbanzo bean), guar, and
peas including garden pea, field pea, sugar
(Stall, Vegetarian 90-05)
knowing Herbicides Used
As land for long term rotations
becomes less available, growers are forced
to more intensively use the same land.
We all know of the increased disease risk,
however, one problem often overlooked is
herbicide carryover from the previous
As grain and other agronomic crop
producers include more vegetables into
their rotational programs extreme caution
must be used in selecting herbicides for
each crop. Several new herbicides have
recently been labelled for soybeans and
small grains. Some of these materials
have rotational restrictions for greater
than 12 months for vegetables, many even
restrict planting vegetables for 18 months.
There have been several instances
this spring of damage to vegetables from
herbicide residue from previous agronomic
crops in north Florida.
Growers must read all herbicide
labels carefully prior to use on a crop this
year. Make sure the planned crop for the
treated field next year is going to be OK.
Make notes and keep good records on
each field including the herbicide applied,
rate applied and date applied.
Herbicides that have long waiting
periods before vegetables can be safely
grown include: Gemini, Scepter, Canopy,
Atrazine, Pursuit, Command, Ally Classic,
Gleam, Harmony, Squadron and Triscep.
This list contains only a few of the
popular herbicides and many more
materials have specific recropping
restrictions. As always read the label
entirely to avoid future problems.
(Bob Hochmuth, Vegetarian 90-05)
IV. VEGETABLE GARDENING
A. Tomato Leaf Roll.
Always at this time of the
year, as the peak of the spring gardening
season approaches, Extension gets a lot of
inquiries from gardeners about the
mysterious curling of their tomato leaves.
With the usual dry soil conditions
associated with early May throughout the
state, we would expect to see some
amount of leaf curl due to the drought.
However, with such plants, wilting would
also be noted, and with the addition of
water through irrigation, the plants would
tend to straighten back out.
Another fairly common cause of
leaf curling in Florida gardens is the
pseudocurly-top virus. It is reported (in
Bulletin-731, Tomato Diseases in Florida)
to be transmitted from weeds such as
ragweed and nightshade to the tomato
plant by treehoppers. It usually occurs on
young plants in the fall season. The
curling is described as an upward rolling
and twisting of the leaflets exposing the
undersides. The plant is brittle, yellow,
and often purple-veined. The severely
shriveled plants seldom set fruit after
infection, and the plants never recover.
In most instances the leaf curling
condition fits the description given for
common leaf roll, a non-pathogenic
disorder. It occurs regularly in gardens
(and fields) all over the state particularly
during the middle to the latter half of the
growing season. This leaf roll hits the
plant about the time of fruit set of the
first and second clusters. The leaves
begin to curl very rapidly. As the rolling
progresses, the leaves take on a
cylindrical shape and become brittle, stiff,
and somewhat leathery. Plants generally
are not stunted and are reported to
produce fruits as usual.
The cause of this latter leaf roll
condition is not fully known. It appears
to be worse on heavily pruned plants and
during periods of heavy rainfall. The
condition also has been linked to
ammoniated sources of nitrogen. There
are no control measures to suggest. Since
it is not known to be caused by virus or
other pathogens, removal of the plants is
(Stephens, Vegetarian 90-05)
Prepared by Extension Vegetable Crops Specialists
Dr. D. J. Cantliffe
Dr. D. N. Maynard
Dr. W. M. Stall
Dr. G. J. Hochmuth
Dr. S. M. Olson
Mr. J. M. Stephens
Dr. J. M. White
Dr. S. A. Sargent
Asst. Professor (Editor)
Dr. C. S. Vavrina