Southeastern U.S. Vegetable Crop Handbook - 2023 - 119

Plant spacing requirements for mini seedless watermelon
are considerably less than spacing requirements for normal seedless
watermelon production. Some mini seedless varieties will
need to be planted close in order to maintain an average size of
7 pounds or less. As little as 10 square feet per plant might be
necessary. For example, if rows are spaced on 6 ft. centers, mini
watermelon plants should be spaced 1 ½ to 2 ft. apart within the
row.
SPECIAL NOTES FOR PEST MANAGEMENT
DISEASE MANGEMENT
A. Keinath, Plant Pathologist, Clemson University and R.
A. Melanson, Extension Plant Pathologist, Mississippi State
University
Fusarium Wilt: Fusarium wilt of watermelon is widespread
throughout the southeastern US. Most varieties of watermelon,
other than many heirloom varieties, are resistant to race 0. Many
seeded (hybrid diploid) and seedless (triploid) varieties are
resistant to race 1. Race 2 is present throughout Florida, Georgia,
South Carolina and is likely in other states. No watermelon
varieties are resistant to race 2. Currently, grafting is the only
cultural practice available to manage Fusarium wilt race 2. The
superscripts " S " for susceptible, " MS " for moderately susceptible,
" IR " for intermediate resistance, and " R " for resistant are
listed next to each recommended variety. These superscripts indicate
the reaction of commonly grown diploid and triploid varieties
to Fusarium wilt race 1. Growers should choose resistant
varieties whenever possible, including pollenizers for seedless
watermelon production. Delaying transplanting until soil warms
to 81°F at 4-inch depth will reduce the overall number of diseased
plants.
Gummy Stem Blight: Gummy stem blight is the most common
foliar disease on watermelon in the Southeast. Crop rotation
away from cucurbits for two full years will improve the efficacy
of most fungicides. Bury crop debris as soon as possible after
harvest; do not leave crowns of plants on plastic-mulched raised
beds, which allows the fungus to survive. See Example Spray
Program for Foliar Disease Control in Watermelon Production.
Cucurbit Downy Mildew (CDM): CDM can be a devastating
disease of cucurbits in the southeastern and eastern U.S. Successful
CDM management often requires the use of an appropriate
fungicide spray program. A useful tool for management of
CDM is the CDM forecasting system (http://cdm.ipmpipe.org).
This program depends on the accurate reporting of CDM in the
field as well as the monitoring of a network of sentinel plots
throughout the United States and Canada by plant pathologists
at various Land Grant Universities. Forecasts of the movement
of the pathogen are generated 3 times a week. Risk maps are
produced from these forecasts. For forecasts, maps, text alerts,
and other helpful information please visit http://cdm.ipmpipe.
org. If you think you have CDM, please contact your local Extension
office.
INSECT MANAGEMENT
Cucumber Beetle: Watermelons are resistant to bacterial wilt;
however, control may be needed to prevent feeding damage
to seedlings. Treat when an average of two beetles per plant is
found.
Aphids: Aphid feeding can stunt young transplants and delay
fruit maturation. Thorough spray coverage beneath leaves is important.
Treat seedlings every 5 to 7 days or as needed.
Mites: Mite infestations generally begin around field margins
and grassy areas. CAUTION: DO NOT mow or maintain these
areas after midsummer because this forces mites into the crop.
Localized infestations can be spot-treated. Note: Continuous use
of pyre- throids may result in mite outbreaks.
HARVESTING AND STORAGE
See Table 14 for postharvest information.
2023 Vegetable Crop Handbook for Southeastern United States
119
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