, UNIVERSITY OF Cooperative Extension Service
SFLORIDA Institute of Food and Agricultural Sciences
SA Vegetable Crops Extension Publication
Horticultua &ience Dcpartmcnt P.O. 110690 Cainesvillc, FL 32611 Telephone (352)392-2134
July 1, 1998
I. NOTES OF INTEREST
A. Vegetable Crops Calendar.
II. COMMERCIAL VEGETABLES
-4 A. Watermelon Fruit Defects.
B. Everglades Agricultural Area.
C. Between-Crop Management Practices Will Influence
D. Tomato Institute Program.
IIl. VEGETABLE GARDENING
A. Using Pressure Treated Wood in Vegetable Gardens.
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.
I NOTES OF INTEREST
A. Vegetable Crops Calendar.
July 28-30, 1998. 4-H Horticulture
Training Track and Competitive Events. State 4- H
Congress. Contact Jim Stephens.
September 9, 1998. Tomato Institute, Ritz
Carlton, Naples. Contact Charlie Vavrina. See
program on page 4.
II COMMERCIAL VEGETABLES
A. Watermelon fruit defects.
This is a continuation of my reports on
watermelon fruit defects that began in the March
issue of the Vegetarian with a discussion of
hollowheart and continued in the May issue with a
report on rind necrosis. Several other defects are
included in this article.
Blossom-end rot. Symptoms begin as a
softening and shriveling of the blossom end of
partially-grown fruit and progress to a dark-brown,
sunken, leathery lesion. Varieties producing
elongated fruit are more susceptible to blossom-end
rot than those producing round fruit (Hammouda,
The incidence of the disorder is increased
under low calcium regimes (Waters and Nettles,
1961). Recommendations for control of blossom-
end rot include liming of soil according to soil test
results and maintenance of an adequate, uniform
soil moisture through irrigation management
(Kucharek and Hopkins, 1992).
Bottleneck. Constricted growth at the
stem end of the fruit characterize this disorder. It
is attributed to inadequate pollination either
because of a low bee population or to poor
conditions for bee activity such as cold, wet, or
windy weather. The cause of the misshapen fruit
can be verified by a cut fruit which will show an
absence of seed at the stem end of the watermelon
Sunburn. This disorder appears on the
upper fruit surface as a gray area where the rind
pigment has been destroyed by high temperature.
Watermelon rind temperature reached 107'F in the
sun and was 97F in the shade when air
temperature was 89F (Maynard, 1991
unpublished). Sunburn damage may be avoided
somewhat by selection of varieties with light
colored rinds which are less subject to sunburn
than dark-rinded varieties. The best means of
circumventing sunburn damage, however, is to
provide conditions for good vine growth which
provides shade for the watermelon fruit.
Cross stitch. This disorder appears as a
series of 1 to 2 cm long necrotic wounds that are
perpendicular to the longitudinal axis of the fruit.
It was observed in Indiana in the late 1980's and
early 1990's and in Florida in 1990 where the name
was coined (Latin, 1993).
Greasy spot. Relatively inconspicuous
raised, circular, olive-green areas on the rind
surface characterize this disorder first described in
Florida. Greasy spot occurs rarely and is thought
not to be of economic concern (Latin, 1993).
Target cluster. Distinctive target-like
configurations occur on the rind surface, usually in
clusters of three or more (Latin, 1993). It has been
suggested, because oftheir unique appearance that
the causal organism may be a ringspot virus, but
this has not been confirmed. The disorder is not
common but I have noted it in Florida and in
Hammouda, A. M. 1987. Blossom-end rot of
watermelon in the southern region of
Oman (Dhofan). J. Agr. Sci., Camb.
Johnson, F. A. 1992. Pollination. p. 9-10 in
D. N. Maynard (ed.) Watermelon
production guide for Florida. Florida
Coop. Ext. Serv. SP 113.
Kucharek, T. A. and D. L. Hopkins. 1992.
Disease management. p. 39-40 in D. N.
Maynard (ed.) Watermelon production
guide for Florida. Florida Coop. Ext.
Serv. SP 113.
Latin, R. 1993. Diseases and pests of
muskmelons and watermelons. Purdue
Univ. Coop. Ext. Serv. BP-44.
Waters, W. E. and V. F. Nettles. 1961. The
effect of calcium on growth responses, sex
expression, fruit responses, and chemical
composition of the Charleston Gray
watermelon. Proc. Amer. Soc. Hort.
(Maynard, Vegetarian 98-07)
B. Crop rotations in the Everglades
Palm Beach County produces $1.2 billion
worth of agriculture production annually. The
western half of the county comprises the area
designated the Everglades Agricultural Area
(EAA). This area accounts for over $800 million
of the Palm Beach County production.
Vegetable production in the EAA was king
during the World War II era, followed by cattle in
the 1950's and 60's, and then superseded by
sugarcane in the current era. While livestock has
totally disappeared, vegetables have remained an
important industry, amounting to $75 million per
While there are many small acreages that
each owner calls a "farm", there are less than 100
farms in the EAA that account for 99.9% of the
production. Two farms have the 3,000 acres of
celery, 3 have the 13,000 acres of radishes, 4-5
have snapbeans, 5 have the 3,000 acres of leafy
vegetables, 7-10 have the 24,000 acres of rice, 10
have the 14,000 acres of sod, 15-20 have the
25,000 acres of sweet corn, and 104 have
sugarcane. In other words, nearly every vegetable,
rice, and sod grower in the EAA also grows
sugarcane. This is because sugarcane can take a
beating from the weather and still produce a crop.
It is used as a very effective insurance crop by the
Sugarcane, harvested from 360,000 acres
annually in Palm Beach County, is the major crop
in the EAA. It is harvested 15 months after
planting and re-harvested every 11 months until
yields drop off. Currently, on average, sugarcane is
on a three year cycle before being replaced. Land
coming out of sugarcane is either immediately
replanted to sugarcane (called consecutively
planted sugarcane), rotated to vegetables for 3
years, rotated to sweet corn for a spring or fall
crop, rotated to rice for the spring/summer, or left
as either flooded or weedy fallow.
Consecutively planted sugarcane gives an
economic boost to the grower by not losing a
harvest season. Although this sugarcane-sugarcane
rotation results in a yield reduction, the continuity
of income still is an economic incentive. However,
when a grower tries to consecutively plant
sugarcane for three cycles in a row, yield reduction
results in an economic loss. In other words, every
six years a sugarcane grower must practice some
form of crop rotation. A 6 month sugarcane-free
period is the industry norm.
Acreage under the 6 month sugarcane-free
fallow period, and the summer fallow for leafy,
radish, and celery vegetable acreage, were
traditionally kept under an 8-12 week flooded-
fallow, or a weed free dry fallow. The flooded-
fallow continues to be highly recommended by
IFAS because it conserves soil and reduces pest
Flooding organic soils during the summer
is a sound agronomic practice. Environmentally,
the EAA is a hot bed of activity stemming from the
alleged influence of agriculture on the phosphorus
content of water entering the Water Conservation
Areas and the Everglades National Park. In
reality, most of the measurable nutrient problems
in surface water stem from two sources;
mineralization of the organic soils releasing bound
phosphorus, and nutrients entrained on particulate
matter carried by drainage water entering canals.
When the old Everglades swamp was
originally drained, three things happened. First, the
soils compacted, resulting in a loss of about 30%
of their original thickness. Second, in the presence
of air, the soil began to mineralize, releasing
nutrients to the soil and water and carbon products
to the air and water. Third, wind erosion became
a factor. The resultant loss of surface elevation
accounted for by these three forces of nature is
referred to as subsidence. The EAA, on average,
lost a half an inch of soil per year during the past
ten years. Soil depth to bedrock across the 550,000
acre EAA is currently estimated to average around
Mineralization of the organic soil is both a
chemical and a biological process accelerated by
heat and the presence of oxygen. By reducing or
eliminating the presence ofoxygen, mineralization
is significantly slowed. Under flooded conditions,
mineralization and both wind and water erosion are
control led, virtually eliminating soil loss. However,
normal farming practices dictate well drained soils
during most of the growing season. By flooding
during the fallow summer period only, which is the
time of the highest temperatures and rates of
mineralization, soil losses can be significantly
Because rice is grown under flooded
conditions and in the heat of the summer, it is
nearly the perfect method for slowing subsidence.
Rice grown strictly for a cover crop significantly
improves soil tilth when incorporated. When grown
as a cash crop, it pays for land improvements and
flooding costs, and in many years, returns a small
profit. Marketing rice is dependent on a processing
mill and favorable markets. Since both are present
in south Florida, rice is a natural.
In summary, vegetable production in the
EAA occupies a site for three years, including a 4-
5 month fallow period during the heat of the
summers. Sugarcane production occupies a site for
sixyears followed by a 6 month fallow period, also
during the heat of the summer. Keeping these
vacant fields under water stops subsidence during
these flooded periods and eliminates many pests
that would otherwise require chemical controls. In
addition, rice can be successfully grown in the
EAA during the warm summer months and needs
flooded conditions. Rice accomplishes everything
a fallow-flood would plus gives an economic as
well as agronomic return.
(Thomas J. Schueneman, is Vegetable Agent with
the Palm Beach County
Cooperative Extension Service
C. Between-crop management practices
will influence future productivity.
To leave a field "fallow" connotes
inactivity. Fallow actually means that tillage has
been completed but nothing has been seeded.
Occasional tillage must be performed to control
weed growth. While it is used primarily for weed
control, fallowing is also very effective in
controlling other pests such as wire worms. By
taking away their food source, disease and insect
pest pressure is reduced. However, it is nearly a
worthless practice if it is not managed. A neglected
fallow field is nothing more than a weed-seed
Weeds produce thousands of seeds that sit
and wait for favorable conditions under which to
germinate and rob the cash crop of nutrients,
water, and light. Weeds are a reservoir for pests
and disease, interfere with cultivation and harvest,
and reduce crop quality. While weed control
requires active management, a neglected fallow
period only exaggerates the problem. Why not
change the word "fallow" to "between-crop
management" and get some good out of idle fields.
Immediate incorporation of crop residue
after the last harvest begins the between-crop
management. This minimizes the impact of that
field being a breeding site for pests that a
harvested, abandoned field has on neighboring
crops. Weed growth is stopped.
This tillage operation will encourage a
flush of weed seeds to germinate now, but these
will be removed, thereby reducing weed pressure
later. As soon as the above mentioned weeds are
visible, a cover crop should be planted. Using the
proper equipment, the shallow tillage required for
drilling the cover crop will also eliminate the weed
flush in a one-pass operation.
Growing a cover crop has many
advantages over a clean fallow and almost no
disadvantages. It reduces soil erosion, reduces
nutrient leaching by incorporating left over crop
nutrients into the cover crop, smothers weeds,
improves soil tilth and drainage, and increases the
substrate necessary for good soil microbial activity.
The cover crop can easily be used for
green manure. Nutrients can be incorporated into
the crop, and then returned to the soil as a slow
release nutrient source for the succeeding crop.
Again, it must be managed. Good growth for the
green manure crop is essential, so supplemental
fertilizer may be needed to maximize efficiency.
Cover crops should be incorporated before
they go to seed. Also, most green manure cover
crops have the capability of tremendous top
growth. Incorporation must be done before
excessive growth becomes a cultural problem.
Under normal Florida conditions fresh
cover crop residue is quickly broken down by soil
micro-organisms, releasing nutrients for plant use.
A three week lead time from cover crop
incorporation to cash crop planting is probably
sufficient. Usually within six weeks of
incorporation, few traces ofthe cover crop can be
In summary, cover crops reduce erosion,
scavenger excess nutrients from the preceding crop,
improve tilth, suppress weeds, and improve water
relationships in the soil. With a little additional
management, a green manure cover crop does all
these plus stores more nutrients and acts as a slow
(Thomas J. Schueneman, is Vegetable Agent with
the Palm Beach County
Cooperative Extension Service
Tomato Institute Program
Ritz Carlton, Naples
September 9, 1998
Opening Remarks Edward Hanlon, SWFREC,
Free Trade Agreement of the Americas: Current Status and Future Opportunities for Florida Tomato
Growers John Van Sickle, IFAS, Food & Resource Dept., Gainesville
Update on tomato yellow leaf curl virus Jane Polston, Virologist, IFAS, GCREC, Bradenton
Phytophthora capsici: New problems from an old enemy Robert McGovern, Pathologist, IFAS,
Update on the use of bacteriophages for control of bacterial spot Jeff Jones, Pathologist, IFAS,
10:30 a.m. Bacterial speck: The other bacterial disease Ken Pernezny, Pathologist, IFAS, EREC, Belle Glade
10:50 a.m. The scientific, economic, and political reality of the phaseout of methyl bromide Joe Noling,
Nematologist, IFAS, CREC, Lake Alfred and Jim Gilreath, Weed Scientist, IFAS, GCREC Bradenton
11:10 a.m. Effect of commercial bacterial and fungal microorganisms to colonize tomato roots and control
Fusarium crown and root rot under fumigated and non-fumigated conditions Lawrence Datnoff,
Pathologist and Ken Pernezny, Pathologist, IFAS, EREC, Bradenton.
III. VEGETABLE GARDENING
A. Using pressure treated wood in
Here is one of the most frequent gardening
questions I get: "Is it safe to use pressure treated
lumber in the vegetable garden?" I hope to answer
this question with the following article. I received
most of my information from an article by Ruth
Lively in Kitchen Garden, June-July 1998, and
George Liebig, Jr., University ofCaliforia, 1965,
Diagnostic Criteria for Plants and Soils.
Wood uses. Gardeners use lumber in the
garden in a variety of ways. The most popular use
is for the construction of border-boards for gro-
boxes (raised beds). Boards in dimensions ranging
from 2x6 inches to 2x12 inches provide a sufficient
root zone depth. Most gro-boxes are constructed 4
to 5 feet wide to accommodate reaching into the
raised beds for planting, weeding and other tasks.
Most raised beds are constructed 8-10 feet long.
Wood is also popular with gardeners for
staking, trellising, fencing, and construction of
compost bins. Since all of these uses involve soil
contact, decay-resistant lumber is needed.
Naturally- resistant wood such as cedar, redwood,
and cypress is sometimes used, as is lumber that is
treated with creosote, pentachlorophenol, asphalt,
and paint. However, the cheapest, most readily
available, and longest lasting decay resistant wood
is pressure-treated lumber (PTL).
PTL. To pressure-treat lumber for rot and
insect resistance, it is sealed in a vacuum tank.
Then a solution of chromium, copper, and arsenic
(CCA) is added. The vacuum moves the solution
deep into the wood.
Arsenic concerns. Of the three toxic
ingredients in PTL, arsenic raises the most
concerns, although chromium and copper are also
feared. Organic arsenic occurs throughout nature,
including in our foods, but the arsenate used in
wood is inorganic. People in general fear the word
arsenic because it is a well known ingredient in
rodent and insect poisons. Arsenic by itself is not
poisonous, but many of its compounds are
extremely so. Calcium arsenate, lead arsenate, and
cupric arsenite (Paris Green) have been used as
What's new in the industry- Industry Representatives
Agricultural labor in southwest Florida Fritz Roka, Economist, IFAS, SWFREC
The food quality protection act & the FL grower Dan Botts, Environmental & Pest Management
Florida Automated Weather Network: A tool for growers- John Jackson, Ext. Agent Ill, IFAS, Lake
County Extension Service
Tomato transplant cell size effects earliness and yield Charlie Vavrina, Horticulturist, IFAS, SWFREC
Prospective releases from the University of Florida tomato breeding program Jay Scott, Breeder,
Update on the Florida premium-quality tomato program Steve Sargent, Postharvest Specialist, Hort.
Science Dept., IFAS, Gainesville
Tomato fertilization recommendations-evaluation and review George Hochmuth, Extension Specialist,
Hort. Science Dept., IFAS, Gainesville
(Vavrina, Vegetarian 98-07)
insecticides in agriculture for a long time. Sodium
arsenite and arsenic trioxide are well-known
herbicides. Arsenic sprays have been used to hasten
the maturity of citrus fruits.
Of course, arsenic should be feared in
acute toxic doses. Large doses can be fatal, while
lesser amounts can cause other health problems.
Even though arsenic can't be avoided totally,
everyone wants to eliminate as much ingestion as
possible. Author Lively quotes the Agency for
Toxic Substances and Diseases Registry (Atlanta)
as reporting that we can ingest up to 0.3
micrograms of inorganic arsenic per kilogram of
body weight per day without harm.
So the big concern is: does the arsenic
leach out of the wood into the garden soil and
become taken up by the vegetables in amounts
large enough to cause health problems?
Leaching studies. According to Lively, a
study involving utility poles in Canada showed that
the wood placed in the soil does leach small
amounts of CCA over time.
To determine the distance arsenic travels
from the wood into the soil, Lively sent samples
from a 3-year old framed bed to a lab for testing.
Her soil without PT wood had4 ppm arsenic. With
PT wood, it showed 20 ppm arsenic up to 2 inches
from the wood, but showed only 4 ppm at 6-inch
and 24-inch distances. Thus, even though arsenic
may leach, it doesn't move very far from the wood.
Wood scientists concluded that the potential for
groundwater contamination from garden use of
CCA is pretty much zero.
Arsenic in soils and plants. The fact that
arsenic is a natural component of soils was
illustrated by Liebig who reported a survey of
virgin and other soils showing a range of 0.3 to 38
ppm arsenic (only 20 percent had more than 10
ppm). Sandy soil generally has the lowest levels.
Early surveys showed that levels of arsenic
in native plants and vegetables grown on natural
soils did not exceed 10 ppm. However, soil
contaminated with arsenic did produce vegetation
of higher arsenic content than uncontaminated
soils. Accumulations of arsenic in soils can have
detrimental effects on plant growth. Since arsenic
accumulates in larger amounts in or on the roots,
root rotting usually occurs in solution culture (and
may be evidenced by leaf wilting and plant
stunting). Plant growth becomes limited before
arsenic can be translocated to the tops. Seed
germination and seedling viability are greatly
reduced with toxic levels of arsenic.
Lively reported on three studies of
vegetables grown on arsenic-enhanced soils. It was
found that at certain levels, arsenic did interfere
with the growth of some plants, such as beans, but
did not affect others, such as tomatoes and carrots,
as much. According to Liebig, vegetables may be
classified as to tolerance of arsenic in this way:
Tolerant: asparagus, potato, and tomato, carrot.
Fairly tolerant: strawberry and sweet corn on
heavy soils; beets and squash. Low or no
tolerance: snap bean, limas, peas, other legumes,
onion, cucumber, and strawberry and sweet corn
on light soils.
Lively reported that there was no
correlation between a crop's sensitivity and its
arsenic content. Even where arsenic was high
enough to reduce yields by 50%, spinach contained
only 1 ppm arsenic and radishes only 8 ppm.
Carrots grown with arsenic-laced soil had 0.11
ppm arsenic, as compared to 0.05 ppm in soil
So, is CCA treated wood safe? Lively
talked with several food safety experts: Michigan
State'sBourquin:"Consumers like to have zerorisk.
Compared to microbial risks, arsenic exposure
doesn't seem a big problem." USDA's Chaney:
"There's no evidence that food safety is impaired
by growing vegetables around CCA-treated wood."
But the USDA spokesman did point to the
possibility of a health hazard from touching the
wood and transferring the arsenic in that way.
University of New Brunswick's Cooper: "Do not
make compost bins from treated lumber because
the acids arising from composting cause more
leaching and reduces lumber's integrity."
My opinion: While the risks from
ingesting arsenic in crops growing near CCA
treated lumber used in the garden appear to be
relatively remote, they are possibility. Therefore,
anyone not comfortable with taking the risk,
however small, should use alternatives or
1. Use alternative materials, such as plastic
and concrete, or naturally decay-resistant
lumber like cedar and cypress, or treated
woods that do not contain arsenic.
2. Handle the CCA treated wood with
caution; wear gloves and a dust mask
when cutting it. Don't use the sawdust in
the garden or compost pile. Don't bur the
wood and inhale smoke.
.3. Wash and scrub the lumber first to remove
any surface residues. Let the lumber
weather several months before cutting and
4. Paint the lumber or cover with a plastic
5. Do not plant root crops. If planted, sow
seeds at least 6 inches from the boards.
You mightplant flowers between the wood
and the vegetables.
6. Do not mix the soil close (2 inches) to the
boards with soil further out in the bed.
7. Amend soils with organic matter to reduce
the soluble arsenic content in soils.
(Stephens, Vegetarian 98-07)
Prepared by Extension Vegetable Crops Specialists
Dr. G. J. Hochmuth
Dr. S. A. Sargent
Dr. S. M. Olson
Dr. C. S. Vavrina
Professor & Editor
Dr. D. N. Maynard
Dr. W. M. Stall
Dr. J. M. White
Dr. T. E. Crocker
Dr. D. J. Cantliffe