INSTITUTE OF FOOD AND FLORIDA
S AGRICULTURAL SCIENCES COOPERATIVE
UNIVERSITY OF FLORIOA EXTENSION SERVICE
UNIVERSITY OF FLORIDA VEGETARIAN
A Vegetable Crops Extension Publication
Vegetable Crops Department 1253 field Hall Gainesville,FL 32611 Telephone 392-2134
Vegetarian 91-12 December 18, 1991
I. NOTES OF INTEREST
A. Vegetable Crops Calendar.
B. 1992 Sweet Corn Institute Canceled.
C. New Publications
SD. Suwannee Valley Field and Greenhouse Vegetable
Grower's Shortcourse and Trade Show
E. Field Vegetable Session Extension Conference
F. Greenhouse Vegetable Session Exhibition H
II. COMMERCIAL VEGETABLES
A. Seedless Watermelon Variety Trial Results, Spring
SB. Plant Sap Testing Protocols
III. PESTICIDE UPDATE
SA. Weed ID Guide from Southern Weed Science
I TV. VEGETABLE GARDENING
A. Vegetable Gardening Guide 1991 Revisions
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 information and does not necessarily
constitute a recommendation of the product
The Institute of Food and Agricultural Sciences is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research, educational
information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap or national origin,
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS, STATE OF FLORIDA, IFAS, UNIVERSITY OF FLORIDA,
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I. NOTES OF INTEREST
A. Vegetable Crops Calendar.
January 11, 1992. Suwannee Valley
Field and Greenhouse Vegetable Grower's
Shortcourse and Trade Show. Suwannee
County Coliseum, Live Oak. (See D, E, F)
February 8, 1992. 4-H/FFA Horticul-
tural Plant ID Contest. Florida State Fair,
Tampa. (Contact Jim Stephens).
March 5-6, 1992. Postharvest Horti-
culture Institute. University Centre Hotel,
Gainesville. (Contact Steve Sargent).
March 9-12, 1992. Harvest and Post-
harvest Handling of Horticultural Crops.
Tour of Central and South Florida.
(Contact Steve Sargent).
March 15-19, 1992. Second Interna-
tional Symposium on Specialty and Exotic
Vegetable Crops. Miami (contact Don
1992 Sweet Corn Institute
The Sweet Corn Institute which had
been scheduled to be held in February in
1992 has reluctantly been canceled. The
Vegetable Crop Extension Specialists and
Agents during the planning session agreed,
(not unanimously) to cancel this years pro-
gram. It is felt that the limited remaining
resources and travel budgets should be
allocated to higher priority areas or more
pressing needs. Priority program planning
has been a must this year and several
programs such as the Watermelon Institute
and the Sweet Corn Institute have had to
be postponed for at least a year.
The information to be extended at the
institute will be made available to the
sweet corn industry through other sources.
(Stall, Vegetarian 91-12)
C. New Publications.
FL 4-H Horticulture ID and Judging
Manuals. (FFI-Kathleen Ruppert, E. Hort.)
The following Suwannee Valley AREC
Extension Reports written by Robert
Hochmuth, et al. are available from the
AREC, Live Oak.
Results of Four Muskmelon Cultivar
Trials. Report 91-1.
Comparison of Degradable Mulches
When Growing Transplanted and Direct-
Seeded Watermelons in North Florida.
Degradable Mulches for Watermelons.
Short Day Onion Cultivars for North
Florida. Extension Report 91-4.
Nitrogen Crop Nutrient Requirements
for Muskmelons Grown in Various Poly-
ethylene Mulch Systems. Report 91-5.
Muskmelon Cultivar Trial Spring 1990.
Seedless Watermelon Cultivar Evalu-
ation, 1990. Report 91-7.
Seedless Watermelon Cultivar Evalu-
ation, Spring 1990. 91-8.
Yield and Quality of Standard and
Precocious Yellow Squash Cultivars.
Polyethylene Mulch and Transplants
Increase Early Watermelon Production in
North Florida. Report 91-10.
D. Suwannee Valley Field and
Greenhouse Vegetable Grower's
Shortcourse and Trade Show.
Suwannee Valley Coliseum, Live Oak, FL
January 11, 1992
8:30am Registration and Trade Show
(coffee and donuts)
AM Concurrent Sessions (choose one)
Field Vegetable Session (see E.)
Greenhouse Veg. Session (see F.)
Lunch and visit exhibits
PM Concurrent Sessions (choose one)
1:15pm Greenhouse Vegetable Session or
Field Vegetable Session
Meal reservations at $5.00 each are
required by January 7, 1992, Call 362-1725.
*Credits (CEUs) will be granted for each
session toward renewal of certification for
Sponsored by: IFAS & area agribusinesses.
E. Field Vegetable Session Exten-
sion Conference Room.
9:45am WELCOME: Steve Ryan, IFAS
9:50am Agriculture and Migrant Labor,
Walter Kates, FFVA
10:40am Florida License and Bond Con-
sidering Changes, Jim Brooks
ll:00am Research on Controlling Sweet
Potato Whitefly With Detergent
Sprays, Charles Vavrina, IFAS
11:30am Tips for Successful Stand
Establishment of Peppers,
Charles Vavrina, IFAS
1:15pm Making Double Cropping on
Plastic Mulch Work for You,
George Hochmuth, IFAS.
2:00pm Testing Plant Sap A New, Quick
Field Test for Managing Ferti-
lizer Programs, Jim Fletcher,
F. Greenhouse Vegetable Session -
Exhibition H Building.
9:45 am WELCOME: John Woeste, IFAS
10:00am Tips for Growing and Fine
Tuning Vegetable Production in
Rockwool, George Hochmuth,
10:50am In Search of Alternative Crops for
Herbs Michael Dowgert, Agro
Pepper Production and an
Update on Tomato Cultivars -
Jim Farley, DeRuiter Seed,
1:15pm New Disease Issues (new virus-
es, gray leaf spot, alternatives to
Benlate), Gary Simone, IFAS
2:00pm Detecting New Greenhouse In-
sect Pests, Bob Hochmuth, IFAS
3:00pm Open House at Suwannee Valley
5:00 AREC Demonstration Green-
house, Tomato Cultivars,
Peppers, and Eggplant.
* Greenhouse growers are encouraged to
bring a 2-4 ounce sample of their final
nutrient solution with them to the trade
show for a quick (while you wait) analysis
of nitrogen and potassium. This will be
done with easy-to-use ion selective elec-
trode tests. Check in at the registration
desk for this test.
II. COMMERCIAL VEGETABLES
A. Seedless Watermelon Variety
Trial Results, Spring 1991.
Although the procedure for produc-
tion of seedless watermelons has been
known for almost 50 years and commercial
varieties have been available for nearly 20
years, the interest in and acreage of seed-
less watermelons has remained small. Er-
ratic performance, poor seed germination,
high seed costs, and inadequate varieties
resulted in the lack of interest in seedless
Specialty vegetables are in high
demand and seedless watermelons offer an
attractive alternative for the up-scale
consumer and the food service industry.
Seedless watermelons are being promoted
by marketing organizations and seed
companies to stimulate demand. At that
time, new varieties are being developed
that are superior to those already available.
The objective of this trial was to
evaluate the performance of seedless
watermelon varieties and experimental
lines under west central Florida conditions.
Seed of 27 seedless watermelon
varieties or experimental lines were
planted in a peat-lite growing mix in no.
150 Todd planter flats on 13 February.
The watermelon transplants were grown by
a commercial plant grower. The plots were
24-ft long, had eight plants each, and were
replicated three times in a randomized,
complete block design. Icebox and stan-
dard watermelon were direct seeded in
beds on each side of two seedless water-
melon beds on 21 February to serve as
Watermelons were harvested on 14
May and 31 May. Marketable (U.S. No. 1
or better) according to U.S. Standards for
Grades were separated from culls and
counted and weighed individually. Soluble
solids were determined with a hand-held
refractometer on at least six fruit from
each entry from the first harvest.
Early yields, represented by the
first of two harvests, ranged from 13 cwt/A
for 'Honeyheart' to 241 cwt/A for NVH
4296. Early yields of 21 other entries were
statistically similar to those of 'Honey-
heart', whereas 23 other entries had yields
similar to those of NVH 4296. Average
fruit weight ranged from 6.2 lb for 'Honey-
heart' to 13.4 lb for CFREC 89-6 and
CFREC 89-11. Average weight of fruit at
first harvest of seven other entries was
similar to that of'Honeyheart', whereas 22
other entries had average fruit weight sim-
ilar to those of CFREC 89-6 and CFREC
89-11. Accordingly, early yields and
average fruit weight did not vary greatly
among the entries included in this trial.
Fruit soluble solids were uniformly
high ranging from 11.1% for 'Millionaire' to
12.9% for SWM 8702. Accordingly, soluble
solids in all entries exceeded the 10% spe-
cified for option use in the U.S. Standards
for Grades of Watermelons.
Total yields ranged from 261 cwt/A
for CFREC 89-4 to 546 cwt/A for 'Ssuper-
sweet 5032'. Eighteen other entries had
total yields similar to those of CFREC 89-4,
whereas 23 other entries had total yields
similar to those of 'Ssupersweet 5032'.
Average fruit weight for the entire season
varied from 8.4 lb for NVH 4296 to 12.9 lb
for 'Ssupersweet 5032' and 'Ssupersweet
5344'. The average fruit weight of 13 other
entries was similar to that of NVH 4296,
whereas 14 other entries had average fruit
weight similar to those of 'Ssupersweet
5032' and 'Ssupersweet 5344'. Although
total yields far exceeded the state average
yield of about 180 cwt/A for the 1985-86 to
1989-90 seasons, they were considerably
lower than yields from seedless watermelon
trials at Bradenton in the spring 1989 and
1990 seasons. A high gummy stem blight
incidence which was exacerbated by almost
8 inches of rain which occurred in the
latter half of May may have contributed to
For more details on this trial,
request GCREC Research Report
BRA1991-21 from the author.
(Maynard, Vegetarian 91-12)
B. Plant Sap Testing Protocols.
Plant sap testing for nitrogen and
potassium is being more widely adopted in
Florida vegetables. The practice is finding
usefulness with drip-irrigated vegetables,
especially tomatoes for guiding N and K
fertilizer injections. Over the last few
years, IFAS workers have developed sap
testing protocols for vegetables. These
guidelines along with a few other precau-
tions are presented in this article in an
attempt to provide a baseline operating
protocol so that we achieve the best benefit
from sap testing. A listing of critical
ranges for fresh sap nitrate-nitrogen is
presented in "Plant Tissue Analysis and
Interpretation for Vegetable Crops in
Florida", Special Series Report SSVEC-42.
Time of day. Temperature and time
of day influence sap nitrate content.
Research shows that making readings con-
sistently between 10:00 AM and 2:00 PM
gives the most dependable results.
Leaf age. The IFAS calibration
charts for vegetable sap testing were devel-
oped for petioles of most-recently-matured
leaves. These are leaves that have essen-
tially stopped expanding in size.
Leaf part. The tests were calibrated
using the fleshy petiole of the leaf. For
most crops the petiole (leaf stem) is easy to
identify. For crops like tomatoes having
compound leaves, the petiole is the whole
leaf stem with all the small petioliules (and
tiny leaflets) stripped off. In normal situa-
tions the leaf petiole will be about 8 inches
in length. For some crops such as pepper
or eggplant some of the lower part of the
leaf blade can be trimmed away to gain
more petiole per leaf. Trim only about the
lower one inch of the blade away. Throw
out the rest of the blade and midrib.
Number of leaves. Even though
three or four leaves might be enough to
produce a sufficient amount of sap for
testing, you might need to sample addi-
tional plants to be sure the final sap is
representative of the field or zone being
tested. Chop up the leaves, mix, and sub-
sample the chopped petiole pieces to get
the final sample to crush. Usually about
20 leaves are enough to adequately repre-
sent a 5 to 10-acre field if that field is
judged to be uniform. Crops with small,
essentially "dry" petioles (strawberry) will
need to have more petioles collected to get
enough sap compared to fleshy crops such
Equipment. All that is needed is a
garlic press or lemon press to squeeze the
sap from the petiole pieces. However, if
many samples are being tested, then
investment in a hydraulic plant sap press is
well advised. (HACH Company, PO Box
389, Loveland, CO 80539). Other equip-
ment includes sampling knife, scissors,
paper towels, distilled water rinse, chop-
ping knife and board, and testing kit.
Storing petioles. We recently tested
some options for storing samples so that
consultants or others wishing to sample
several farms and then read the sap later
could have more flexibility. It appears that
fresh petioles can be stored on ice for up to
8 hours without appreciable changes in sap
nitrate concentration. Store whole
(unchopped) petioles, not whole leaves.
Strip the blades from the petioles and store
petioles in a plastic bag on ice in a cooler.
Petioles also can be stored at room
temperature in a plastic bag for up to 1 1/2
to 2 hours. Do not store whole leaves or
petioles in open air. Otherwise, the peti-
oles will wilt and nitrate readings will not
be accurate. Always store petioles only.
Do not store sap. Cold petioles should be
warmed to room temperature before read-
ing since temperature differences between
sap and meter might affect results.
Reading time frame. Measurement
of the nitrate content of the pressed sap
must be made within a minute or two of
pressing. Otherwise nitrate readings will
change from the fresh petiole condition.
Test Kit Management
Calibration. Test kits should be
calibrated and tested with standard, known
nitrate and potassium solutions which are
available from the test kit manufacturer.
With the colormetric test kits, the calibra-
tion with a known solution will help tell if
your chemicals are still good. Chemicals
on the test strips or in the powder pillows
of the various kits will deteriorate with
time and with exposure to heat and light.
The electrode testing kit will need to be
frequently calibrated with standard solu-
tions. It is a good idea to check the cali-
bration every 5 or 6 samples. Readings
should be done indoors in the shade.
Avoid direct sunlight on the meter since
this can affect operation of meter.
Calibration scale. Samples should
always read within the calibration scale
(reading scale) of the test kit instrument.
If sample saps are higher than the high
end of the scale, the sap will need to be
diluted. Reading within the calibrated
scale improves accuracy.
Kit care. The sap kits are scientific
tools that need to be properly cared for.
Always store the kits and chemicals in a
protected place and within the proper tem-
perature ranges specified by the manufac-
turer. It is not a good idea to store kits in
the pick-up truck or at the pump house.
Nitrate conversions. Some kits read
out in nitrates and some in nitrate-nitro-
gen. The calibration tables developed by
IFAS are in nitrate-nitrogen values. For
the kits that read out in nitrates (NO3),
you will need to divide by 4.43 to get
nitrate-nitrogen which can then be com-
pared to the IFAS chart values. Potassium
is usually read directly as ppm K+.
Sap versus dried petioles. There
are some published book values for petiole
nitrate-nitrogen. However these book
values are usually based on dried petioles
and are not directly transformable to fresh
sap nitrate-nitrogen concentrations.
(Hochmuth, G., Vegetarian, 91-12)
III. PESTICIDE UPDATE
A. Weed ID Guide from
Southern Weed Science Society.
Several Agents expressed interest in
obtaining the total Weed ID Guide or ob-
taining the later sets of the guide that they
do not have. The Weed ID Guide contains
single page (both sides) identification
information on weeds found in the south-
ern United States. Pictures of the weeds
are in color. Updates and new weeds are
published periodically. Advanced payment
The sets may be obtained as:
Weed ID Guide #1, 1985 @ $15.00 set.
Weed ID Guide #2, 1986 @ $15.00 set.
Weed ID Guide #3, 1987 @ $15.00 set.
Weed ID Guide #4, 1988 @ $15.00 set.
Weed ID Guide #5, 1989 @ $15.00 set.
Weed ID Guide Binder @ $7.00.
They may be obtained from:
Southern Weed Science Society
309 West Oak Street
Champaign, IL 61820
Also, the publication "Research Methods in
Weed Science", 3rd Edition, 1986, may be
obtained for $30.00.
(Stall, Vegetarian 91-12)
IV. VEGETABLE GARDENING
Guide 1991 Revisions.
Soon a newly revised edition of the
Vegetable Gardening Guide (Circular 104)
will be released. This article will deal with
the revisions, but first, let me remind your
that this will be the first edition offered on
a "for-sale" basis.
It remains to be seen how the dis-
tribution process will work, and to what
degree of efficiency. County agents will
need to arrange for purchase of bulk sup-
plies if needed, and then devise a method
for collecting on a per-copy basis. Of
course, anyone will be able to buy a single
copy directly from IFAS Publications. Also,
revisions will show up in one of the next
Now, here is a summary of the
changes and/or additions (revisions) which
you can expect to see in the new Planting
Guide section of the circular. The circular
also includes changes (not reported here)
from the following four colleagues of mine
in their respective areas of responsibility:
Bob Dunn (Nematology), Jerry Kidder
(Soils), Don Short (Entomology), and Gary
Simone (Plant Pathology).
Change 1. Planting Guide Chart: Varieties
Sweet Potatoes: Add 'Sumor'
Tomatoes: Add 'Micro Tom'
Mustard: Add 'Tendergreen'
Onions: Add "Multipliers" -
Spinach: Remove 'Dixie Mar-
ket' and 'Hybrid 7'
Add 'Melody' and
Strawberry: Remove 'Tioga',
'Douglas', and 'Tufts'
Add 'Chandler' and
Change 2. Dates of Planting
Mustard (North): Remove 'Jan-Mar'
Change 3. Plant familv/crop comments
Beans, snap: Add Flowers self-
pollinated. Use shell
beans green or dried.
Cantaloupe: Add Mulch to reduce
fruit rots and sal-
monella. Harvest at
Corn, Sweet: Add Plant in multi-
Cucumbers: Add For greenhouse,
Eggplant: Add Requires warm
Peas, Southern: Add Makes good
summer cover crop.
Pumpkin: Add For big ones, try
Squash: Add Winter types
Tomatoes: Add 'Better Boy'
appears resistant to
Watermelon: Add Florida record-
size melon is
Carrots: Add Sow seeds shal-
low and thin to pro-
Cauliflower: Add For green heads,
Add Well-adapted to
Add Use fresh or
Add Broadleaf type
requires more space.
Add Bulbing onions
may be seeded in the
fall, then transplant
in early spring (Jan-
Add Grow like regu-
Add be sure to trellis.
Add Remove tops 2
weeks before digging
to toughen skin for
Add Inter-crop sum-
mer type with slow-
growing vegetables to
Add Malabar spinach
is a vining, more
prolific type easily
grown in Florida.
Add Grow as an
annual crop using
Change 4. Footnotes
Add Footnote 6. For information on
Malabar spinach and other less-
frequently grown vegetables, get a
copy of Bul. SP-40, Manual of
End of Revisions
Earlier Guides Those of you who
might have stock-piled earlier editions of
Circular 104 (Revised 1987 and 1990) may
continue to use them as handouts. While
these editions do not have the updated
information, they contain no glaring errors.
It is hoped and anticipated that the
new "for-sale" revised edition (104R) will be
ready for the 1992 spring gardening season.
(Stephens, Vegetarian 91-12)
Prepared by Extension Vegetable Crops
Dr. D. J. Cantliffe
Dr. S. M. Olson
Dr. G. J. Hochmuth
Dr. S. A. Sargent
Dr. C. S. Vavrina
Dr. D. N. Maynard
Dr. W. M. Stall
Dr. J. M. White