Title: Vegetarian
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Title: Vegetarian
Series Title: Vegetarian
Physical Description: Serial
Creator: Horticultural Sciences Department, Institute of Food and Agricultural Sciences, University of Florida
Publisher: Horticultural Sciences Department, Institute of Food and Agricultural Sciences, University of Florida
Horticultural Sciences Department
Publication Date: April 1987
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Bibliographic ID: UF00087399
Volume ID: VID00232
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

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INSTITUTE OF FOOD AND
AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA


FLORIDA
COOPERATIVE
EXTENSION SERVICE


VEGETARIAN

A Vegetable Crops Extension Publication

Vegetabic Crops Department -1255 HSPDD GCaincvillc. FL 32611 Telephone 392-213z
IIII1


Vegetarian 87-04


April 17, 1987


Contents

I. NOTES OF INTEREST

A. Vegetable Crops Calendar

B. Unit Name Changes

II. COMMERCIAL VEGETABLES

A. Summer squash varieties differ in
susceptibility to powdery mildew.

B. Arrival condition of Florida tomato shipments
on the New York market, 1972-1984.


C. Carbon monoxide poisoning in the vegetable
industry?

D. Preliminary evaluations of plant sap quick
tests for nitrates.

III. PESTICIDE UPDATE

A. Weed Tour Cancelled

IV. VEGETABLE GARDENING

A. Protecting garden vegetables from frosts.


Note: Anyone is free to use the information in this
newsletter. Whenever possible, please give credit to the
authors.

The use 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, or national origin.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS, STATE OF FLORIDA, IFAS, UNIVERSITY OF
FLORIDA, U. S. DEPARTMENT OF AGRICULTURE, AND BOARDS OF COUNTY COMMISSIONERS COOPERATING








I. NOTES OF INTEREST

A. Vegetable Crops Calendar.


April 28 29, 1987.
been cancelled due to
snap and to the large
rain received.


Weed Tour has
the late cold
amounts of


May 5, 1987. Cucumber/Squash
Variety Demonstration at AREC
Leesburg has been cancelled due to
frost damage.

May 7, 1987. Home Horticulture
Agent In-Service Training has been
cancelled due to shortage of
training funds. The program has
been rescheduled for May 26, 1988.

May 7, 1987. Field Day-Polk County
Mined Lands Research/Demonstration
Project, Bartow, Florida, has been
cancelled due to flooding and frost.

May 12, 1987. Field Day Tomato
water and fertilizer management with
drip irrigation. Artesian Farms,
Ruskin. (Contact Rick Mitchell
(Hillsborough County), Phyllis
Gilreath (Manatee County) or George
Hochmuth. R.S.V.P.)

May 20, 1987. Field Day-IFAS Gulf
Coast Agric. Research Center,
Bradenton.
(Contact Dr. Will Waters).

June 22-26, 1987. State 4-H
Horticulture Institute. Camp Ocala.
(Contact J. M. Stephens).

August 20-21, 1987. Master Gardener
Advanced Training. Reitz Union,
University of Florida, Gainesville.
(Contact Jim Stephens or Bob Black)


B. Unit Name Changes.

Administrative consolidation of the
Apopka, Leesburg, and Sanford
Central Florida Research Units has
resulted in need for establishment


of a single name. Therefore, the
name previously assigned to Sanford
has been selected to encompass all
three units, with the addition of
the location at the end of the name,
i.e., Central Florida Research and
Education Center Apopka, etc. In
the process of reorganization, we
have also made changes in mailing
addresses and hours of operation.
Therefore, the unit names,
addresses, telephone numbers, and
hours of operation are listed below:


Central Fla. REC Apopka
2807 Binion Rd., Apopka, FL
Phone: 305/889-4161
Hrs: 7:30 4:00


32703


Central Fla. REC Leesburg
5336 University Ave.
Leesburg, FL 32748
Phone: 904/787-3423
Hrs: 8:00 5:00

Central Fla. REC Sanford
4700 Celery Ave.
Sanford, FL 32771
Phone: 305/322-4134
Hrs: 7:30 4:00

II. COMMERCIAL VEGETABLES

A. Summer squash varieties
differ in susceptibility to powdery
mildew.

Disease resistant varieties
(cultivars) are recommended for use
whenever they are horticulturally
acceptable and that a particular
disease is likely to threaten the
crop. True disease resistance is
generally lacking in summer yellow
straightneck, yellow crookneck, and
zucchini squash varieties.
However, summer squash varieties do
differ in susceptibility to
diseases, and growers may wish to
select those varieties for planting
that are least susceptible.
Varying degrees of
susceptibility of summer squash
varieties to powdery mildew have







been reported in Homestead (2) and
in Texas (1). In the Homestead
tests 'Cracker', a yellow crookneck,
was found to be least susceptible,
whereas 'Sundance' and 'Dixie' were
most susceptible. In general,
zucchini types were less susceptible
than summer crookneck types;
'President', 'Richgreen', and
'Burpee Hybrid' were the least
susceptible of the zucchinis
evaluated.
Yellow crookneck varieties
least susceptible to powdery mildew
in the Texas trials were
'Enterprise', 'Golden Rebel' and
'Sunbeam'. 'Goldbar' was the least
susceptible straightneck variety.
'ABCO', 'Arlesa', 'Classic',
'Diamate', 'Diplomat', 'Hyzini',
'Rapido', and 'Zucco' were the least
susceptible zucchini varieties.
Some experimental lines in each
squash type had low susceptibility
to powdery mildew.
Differences in susceptibility
among summer squash types was also
noted in the Texas trials as well as
seasonal differences (Table 1).

Table 1. Susceptibility of summer
squash types to powdery mildew in
spring and fall crops.


Mildew Rating1
Squash Type Spring Fall

Yellow Crookneck 2.5 3.0
Yellow Straightneck 2.0 3.0
Zucchini 1.6 2.7
Yellow Zucchini 1.4 2.4

1 = least susceptible, 5 = most
susceptible.

In the absence of disease
resistance, differences in
susceptibility to powdery mildew can
be used by growers in areas where
the disease is particularly
troublesome on a regular basis.


References

1. Holliwell, R. S., J. D. Johnson,
and S. D. Cotner. 1986.
Susceptibility of squash cultivars
to watermelon mosaic virus-I and
powdery mildew fungus. Texas Agr.
Exp. Sta. MP-1617.

2. Pohronezny, K., R. Tyson, J.
Francis, and R. B. Volin. 1985.
Evaluation of summer squash
cultivars for susceptibility to
powdery mildew. Proc. Fla. State
Hort. Soc. 98:268-271.

(Maynard, Veg. 87-04)


B. Arrival condition of
Florida tomato shipments on the New
York market, 1972-1984.

The following information is
from a report by M. J. Ceponis,
research pathologist, ARS, USDA.
Thousands of fresh fruit and
vegetable shipments are examined on
the New York market each year by
trained inspectors of the USDA.
These inspections are paid for by
receivers or shippers who request
the service. Most inspections are
conducted on fresh produce shipments
whose condition for acceptability is
being questioned.
About 70,000 metric tons of
fresh tomatoes are delivered
annually to metropolitan New York,
placing the commodity among the top
10 volume leaders of fresh fruits
and vegetables. Florida supplies
about 45% each year and California
supplies about 25%; the remainder
comes mainly from Mexico, Puerto
Rico, southeastern states, New York,
and neighboring states. During the
period from 1972 to 1984, over 9,000
shipments of fresh tomatoes were
inspected on the New York market and
the results certified. These
inspected shipments made up about
11% of all tomato arrivals on the
New York market. During this same 8






year period, 2729 shipments from
Florida were inspected.
Diseases that originate in the
field were not common, although late
blight rot and phytophthora rot were
reported in fairly substantial
numbers, considering all shipments,
but the number of shipments affected
from Florida was less than 1% for
each of the two rots.
Postharvest diseases,
disorders, and injuries constitute
the major deviation from normal.
Historically, buyers and handlers
have contended that Florida products
are more perishable and nonuniform
in pack compared to products from
other production areas. Certified
inspection of tomatoes at the New
York market does not totally support
this assertion. Listed are the
percent occurrences of the various
abnormalities found by USDA
inspectors, for ALL tomato shipments
inspected (over 9,000) compared to
occurrences on the 2729 Florida
shipments, shown in parenthesis ():
Diseases: Sour/watery rot 35 (39),
gray mold rot 28 (26), bacterial
soft rot 25 (25), decays,
unidentified 24 (25), Alternaria rot
8 (9), Rhizopus soft rot 2 (2).
Disorders: Soft fruit 66 (60),
sunken discoloration 37 (47),
misshapen/cat face 28 (32), growth
cracks 12 (15). Injuries: Shoulder
scars 37 (38), grade defects 16
(44), bruise damage 14 (16).
There is no question that our
pack could be improved, especially
in view of "grade defects", but in
view of extreme variables in weather
during our production season,
arrival condition of our tomatoes is
comparable to those shipped from
other locations.
Recently there have been
unconfirmed reports from terminal
markets of an increased incidence of
watery rot and gray mold rot on
tomatoes from Florida. Watery rot
can best be controlled by careful
handling to avoid mechanical injury
and reducing the temperature of the


fruit down to 55-600F after ripening
has been initiated. Gray mold rot
generally is not a major problem but
is most prevalent in fruit harvested
from old vines during periods of
cool weather, such as we have
experienced during the past few
weeks.

(Gull, Veg. 87-04)


C. Carbon monoxide poisoning
in the vegetable industry?

Recently, national attention
has been directed to planned cases
of carbon monoxide (CO) poisoning,
but is it possible that accidental
CO poisoning might occur in the
vegetable industry?
A County Health Department in
south Florida is investigating a
case in which forklift operators
were hospitalized and the cause was
suspected to be CO poisoning. A
high concentration of CO was found
in the cold rooms where sweet corn
was being stored. Although doors to
the cold rooms are open during
loading and unloading, these
openings are covered by over-lapping
plastic strips.
Concentration of CO in the
rooms did not appear to be
sufficiently high to cause illness
but unaswered questions are (1) was
the measurement of CO accurate, (2)
were there eminations from the corn
that intensified the action of CO
(prevents hemoglobin from taking up
oxygen and thus deprives the body of
the needed oxygen), or (3) was the
high respiration rate of the corn
sufficient to cause a sub-optimum
level of oxygen in the room. The
increased level of CO in the rooms
resulted from partial oxidation of
hydrocarbon gases (incomplete
combustion).
Toxic symptoms of CO are
headaches, mental dullness,
dizziness, weakness, nausea,
vomiting, loss of muscular control,








inadequate, adequate, or abundant
(LaMotte) and low, medium, or high
(Plant Check). The Quant test is
semi quantitative. It involves
dipping a test strip into the plant
sap and reading a color development
intensity on the strip against a
calibrated color chart. Usually a
dilution of plant sap is required
and the time from dipping to reading
is critical. The test is only
semi-quantitative because the
calibration chart is graduated in
fairly large intervals. One
advantage of this test is that it is
very quick; it only requires a few
minutes.
The Hach tests were the most
quantitative tests that we
evaluated. They rely on the same


We plan to continue the
comparisons of the last 3 tests and
to compare the results to those
obtained with standard laboratory
tests. Using final yield data, we
hope to calibrate at least one of
these tests so that it can be used
to make on-the-spot decisions
regarding nitrogen injections via
drip irrigation.

(Hochmuth, Veg. 87-04)


Table 1. Comparison of plant fresh sap nitrate-N content from 3 "quick tests".

N treatment Test
lb/acre Hach spec. Hach hand-held Quant
-------------- ppm sap NO3-N --------------

150 1023z 1036 968
225 1345 1490 1074
300 1380 1516 1300


avg. across 2 water treatments and 3 reps.

colormetric chemistry and are fast.
The hand-held colorimeter seems to
be a suitable alternative to the
more expensive, but very versatile
spectrophotometer. The last 3 tests
are used widely for water quality
determinations and we adapted them
to do plant sap. Their accuracy
will be compared to standard
laboratory tests. The data from the
comparisons of the last 3 tests
appears in Table 1. All 3 tests
detected an increase in plant sap
nitrates corresponding to an
increase in applied nitrogen. The
Quant test reads a little lower than
the Hach tests, and the hand-held
colorimeter reads slightly higher
than the spectrophotometer.


III. PESTICIDE UPDATE

A. Weed Tour Cancelled.

Do to the late cold snap and to
the large amounts of rain received,
the horticultural weed tour has been
cancelled this year.
The plots in the southern part
of the state have to be replanted
due to water damage. Substituting
the tour to other areas was
impossible due to the late freeze
and a 7 inch rain received in those
areas.
We apologize for having to
cancel, but will plan on having a
bigger and better tour next year.


(Stall, Veg. 87-04)









IV. VEGETABLE GARDENING

A. Protecting garden
vegetables from frosts.

April Fool's Day is usually the
day when people play tricks on
people, but April 1, 1987 will be
remembered also, throughout the
South, at least, as the day Mother
Nature played a cruel trick on
gardeners and others growing
vegetables, fruits, and other tender
plants. On two consecutive nights
of April 1 and April 2, temperatures
dipped below 35F all across North
Florida, bringing heavy frost to
some areas and light patches of
frost to others.
Most vegetable gardens around
the state had been planted, except
in areas where heavy rainfall in
March had kept the soil too wet to
plant. Newly-emerged seedlings and
recently planted transplants of such
warm-season crops as tomato, pepper,
eggplant, cucumber, squash, beans,
and sweet corn were either killed
outright, heavily damaged, or
lightly singed, depending on local
variations in severity of the cold
snap.
Now, it is not unusual for
gardeners to plant in the month of
March, but it is unusual for such
low temperatures in the twenties and
thirties to occur so late in the
spring. Records of low temperatures
were set all across the South as the
upper air currents dipped almost
straight down from the artic region
to Florida.
Unfortunately, there is no
definite time-table for the arrival
of spring in the South. This is
because of the gradual way that one
season develops into the next in
southern latitudes. While spring in
the North is a fairly regular
visitor, arriving late but with
little threat of recurring cold,
southern spring is anything but
regular. Here, it is so gradual


that freezing weather may be
expected sometimes for as long as
six weeks after the average date of
last killing frost. Even so, this
year's April-Fool's Day trick took
most of us by surprise.
In the aftermath of the two-day
cold snap, I observed the vivid
results of gardeners' attempts to
protect tender vegetables from the
killing effects of the frost. These
observations prove once more that
those who understand some of the
preliminary facts about frosts, and
who take the necessary steps, can
provide adequate protection in many
instances, especially in small
plots.
Frost occurs most often on
cold, clear nights, preceded by a
day or two of clear skies. On a
clear day, the sun heats up the
soil. If that heat, or a portion of
it, could be saved until about 7:00
in the morning when temperatures are
lowest, then plants might be saved.
The problem is how to save it.
During the day, some of the
heat from the sun is reflected back
to the atmosphere and lost. Some of
it is lost in the evaporation
process of soil water. The heat
that is useful to gardeners is the
heat that is conducted downward
through the soil to depths of four
to ten inches. The most heat is
stored if the soil is bare, if it is
reasonably compact, and is fairly
moist. The idea is for the stored
heat to be conducted upward to the
surface where it can keep the air
and plants warmer.
The soil around plants must be
bare so that the sun shines directly
on it. Any shading or mulching
material will intercept the heat
above ground and liberate it to the
air, so it has little effect on soil
temperature. Thus, mulching
actually increases the risk of
freezing injury.
Also, a loose soil surface such
as produced by cultivation or hoeing
should be avoided. This causes the








soil surface to dry out more
quickly, and the looseness itself
reduces the conductivity of the
soil's heat. Cultivation just
before a frost occurs may result in
more crop damage.
Irrigation in advance is the
most effective way to increase the
amount of heat stored in the soil,
first because some small amount of
heat is added due to the temperature
of the water. Second, irrigation
compacts the soil and firms loose
structure that may have been caused
by cultivation.
Third, watering increases the
heat storage capacity of a given
volume of soil. It has been
estimated that adding 10% of
moisture to the top six inches of
soil will increase the "heat
holding" capacity by 50%.
But the fourth and probably the
most important effect is that moist
soil is a much better conductor of
heat than dry soil. Check out this
principle with a wet pot-holder
sometime, and you'll see that wet
things conduct heat readily. Better
conductivity means that heat will be
conducted deeper into the soil
during the day, and faster and
further upward during the cold
period at night. Thus, a greater
volume of soil can be used for heat
storage and more heat can be
liberated when it will do the most
good. When a frost is forecast,
turn on your irrigation to moisten
the soil before the bright sunshine
has passed on the day previous to
the frost, so as to store up as much
heat as possible.
So far, we have been talking
about ways to increase the amount of
heat stored in the soil, and then
move that heat into the plant zone
during the danger periods. Now my
final point is to mention ways to
trap that heat for a long enough
period of time to reduce damage or
injury from frost. In most cases
the best way to do this is to cover
the plants, using one or more of


several commonly available
materials.
Hotcaps are manufactured and
sold for the purpose of frost
protection. Usually cone-shaped and
made of paper that allows passage of
sun-rays into the protected area,
they do not allow the long-rays to
escape. Place over the plants
(generally one hot-cap per plant or
hill) during the clear day preceding
the expected frost.
Boxes, paper bags, plastic
pots, and such similar devices
should be placed over the plants in
the late evening to trap the heat
stored in the soil. Remove after
the frost period the next morning to
allow the sun to strike the soil for
generation of more heat. Be sure
the bottom of the covering device is
in contact with the soil so that the
heat cannot readily escape at the
bottom.
Cloth materials, such as towels
and old blankets, are good items for
throwing over tender vegetables at a
quick notice. Again, completely
cover the entire plant, late in the
evening after the sun has warmed the
soil during the day.
Plastic tarps make excellent
protective coverings because they
allow the soil to warm up beneath
and then they hold the heat during
the danger periods.
Leaves, pine straw, hay, and
even soil may be used to cover the
plants for two or three days. Keep
the materials dry so as to better
insulate the heat from leaving the
soil and air below and around the
plant. Be sure to scratch out the
seedlings as soon as the danger of
frost has passed.
In summary, gardeners can
reduce the amount of damage and
plant injury that might occur during
late spring frosts by first
understanding how frosts happen, and
then taking a few precautionary
measures. Help the sun warm up the
soil, trap the stored heat, then
allow the heat to move into the area








around the plant. The next time
Mother Nature trys to play an April
Fools Day trick on you, be ready!

(Stephens, Veg. 87-04)



Prepared by Extension Vegetable Crops Specialists


Dr. D. J. Cantliffe
Chairman

Dr. G. J. Hochmuth
Assistant Professor

Dr. S. M. Olson
Associate Professor


Dr. D. D. Gull
Associate Professor

Dr. D. N. Maynard
Professor

Dr. W. M. Stall
Professor


J. M. Stephens
Professor




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