Watermelon Production in Florida                                                                    

 D. N. Maynard

 Botany

 Nomenclature

 Family – Cucurbitaceae

 Watermelon – Citrullus lanatus

 Origin

 Watermelon originated in Central Africa.

Related Species

 Major cucurbit vegetables are cucumber, melon, pumpkin, and the array of summer and winter squash.  Several Oriental and specialty vegetables, including Chinese winter melon, calabash gourd, luffa gourd, bitter melon, and chayote are also included in the Cucurbitaceae family.

 Varieties

 Variety selection, often made several months before planting, is one of the most important management decisions made by the grower.  Failure to select the most suitable variety or varieties may lead to loss of yield or market acceptability.

 The following characteristics should be considered in selection of watermelon varieties for use in Florida:

 Yield: The variety selected should produce crops equivalent to the best varieties available.  In recent years, the average harvested yields per acre of watermelon in Florida have been about 300 cwt.  In most instances, however, harvested yield is usually much less than potential yield because of market constraints.

 Disease Resistance: Varieties that combine disease resistance with other desirable horticultural characteristics should be selected when possible.  Watermelon varieties selected for use in Florida should have resistance to anthracnose-race 1 and fusarium wilt.  There is considerable variation among varieties in the degree of fusarium resistance; select varieties with high wilt resistance that have qualities compatible with other requirements.

 Horticultural Quality: Watermelon fruit size and shape; rind color, thickness and toughness; seed size, number, and color; and flesh color, texture, and soluble solids (10% is required for designation as very good internal quality) are all important characteristics to be considered in selection of watermelon varieties.  Ability to germinate in cold soils and general plant vigor may be important in certain situations.

 Adaptability: Vine crops are well adapted to production in Florida for spring, early summer, and fall markets.  Successful varieties must perform well under the range of environmental conditions encountered in these seasons and in various locations in Florida.

 Market Acceptability:  Watermelon growers must be aware of the needs of the particular market they intend to supply, and grow varieties that produce crops that satisfy that market.

Fertilizer and Lime

 For unmulched crops, incorporate all P₂O₅, micronutrients, and 25 to 50% of N and K₂O in the bed area.  Apply no more than 25% N and K₂O broadcast for subsurface irrigated crops. This “modified broadcast” method improves fertilizer efficiency.  Apply remaining N and K₂O as a sidedressing when vines begin to run.  Supplemental applications of 30 lb N and 20 lb K₂O might be needed after leaching rain.

 For mulched crops under subsurface irrigation, broadcast all P₂O₅, micronutrients, and 20-25% of N and K₂O in the bed area.  Apply remaining N and K₂O in bands in grooves (2 to 3 inches deep) and 8 to 10 inches from the row.

 For mulched crops with sprinkler irrigation, incorporate all fertilizer in the bed before mulching.  Cover with unfertilized soil so fertilized soil is likely to remain moist. Plastic mulch might need to be perforated to provide irrigation infiltration on deep, droughty sands.  Supplemental N and K₂O can be applied by liquid fertilizer injection wheel.

 For drip irrigated crops, broadcast all P₂O₅, micronutrients, and up to 20-25% of N and K₂O in the bed.  Apply remaining N and K₂O through the irrigation tube.

 Soil test and fertilizer recommendations for watermelon mineral soils are given in Table 2.  An injection schedule for N and K for watermelon grown on soils testing very low in K is given in Table 3. 

 Plant Tissue Analysis

Plant tissue analysis information for watermelons is given in Table 4.  The analysis was done at the early bloom stage, using the most recently matured leaf.

 Petiole Sap Testing

 Fresh sap can be pressed from leaf petioles and analyzed fro nitrogen and potassium concentrations.  Results can be sued to make adjustments in the fertilization program.  Sufficiency ranges for sap testing for watermelon plants are presented in Table 5.

Irrigation

 Watermelon water requirements are slightly lower than those of other vegetable crops.  Peak water requirements during rapid growth and development may average 90% of reference evapotranspiration levels (Eto), decreasing to 70% of Eto during the final growth period.  Watermelons have extensive root systems and can obtain available ground moisture, thus reducing irrigation requirements.  It is important to note that excessive irrigation can reduce crop yields by leaching crop nutrients or promoting disease.  However, plant stress from limited water availability will also reduce fruit size and quality.

 

Weed Control in Cucurbit Crops (Muskmelon, Cucumber, Squash, and Watermelon)¹

William M. Stall²

 

 

Crop Competition

An often overlooked tool to reduce weed competition is to establish a good crop stand, in which plants emerge and rapidly shade the ground. The plant that emerges first and grows the most rapidly, is the plant that will have the competitive advantage. Utilization of good production management practices such as fertility, well-adapted varieties, proper water control (irrigation, drainage), and establishment of adequate plant populations is very helpful in reducing weed competition. Everything possible should be done to insure that the crop, not the weeds, has the competitive advantage. Tests with watermelons and muskmelons have shown that if weeds such as smooth pigweed emerge 4-5 weeks after the crops, they will not reduce yield of the crop. If the weed emerges and competes with the crop in the first 4 weeks, however, yield will be reduced by the competition. Two nightshade plants growing in-row between watermelon plants have been shown to reduce yield 80-100% in open culture and 60-75% in mulch culture production.

 

Mechanical Control

Mechanical control includes field preparation by plowing or disking, cultivation, mowing, hoeing and hand pulling of weeds. Mechanical control practices are among the oldest of weed management techniques.

Weed control is a primary reason for preparing land for crops planted in rows. Seedbed preparation by plowing or disking exposes many weed seeds to variations in light, temperature, and moisture. For some weeds this process breaks weed-seed dormancy, leading to early season control with herbicides or additional cultivation.

Cultivate only deep enough in the row to achieve weed control; deep cultivation may prune roots, bring weed seeds to the surface, and disturb the soil previously treated with a herbicide. Follow the same precautions between rows. The roots of watermelons may extend as far as the tips of the vines, even when grown on mulch. Turning the vines and deep cultivation in the vine area may destroy a large number of roots, reducing water and nutrient uptake. Cultivation in a timely fashion is extremely important.

 

Mulching

The use of polyethylene mulch has been shown many times to increase yield and earliness of cucurbits. The proper injection of fumigants under the mulch will control nematodes, soil insects, soil- borne diseases and weed seeds. Mulches act as a barrier to the growth of many weeds. Nutsedge, however, is one weed that can and will grow through the mulch.

 

Herbicides

Properly selected herbicides are effective tools for weed control in cucurbits. Most of the labeled herbicides are for preplant or preemergence applications to the crop and weeds. Only two herbicides are labeled at the present time for postemergent crop applications. Care must be exercised to use these materials at the proper rate and correct time to avoid crop damage. Cucurbits as a group have very limited tolerances to most herbicides.

Two herbicides were removed for use on cucurbit crops by their respective companies in 1985 due to crop injuries resulting from "inadvertent misuse." This severely limits the number of herbicides available for use in Florida.

Before applying a herbicide, carefully calibrate your sprayer. Make sure the proper speed, pressure and nozzles are being used in the field. Worn nozzles can increase gallonage sprayed significantly. Always use the same size nozzles. I have seen booms with 03 and 04 tips side by side.

Most of the new herbicides being tested for labeling on cucurbits have a narrow range of tolerance. A mistake in calibration or application will cause damage to the crop. They must also be applied in the proper manner.

Soil-applied herbicides are either applied to the surface or incorporated. Surface-applied herbicides require rainfall or irrigation shortly after application for best results. Lack of moisture often results in poor weed control, however, they are relatively easy to apply.

Incorporated herbicides are not dependent on rainfall or irrigation and have generally given more consistent and wider-spectrum control. They do, however, require more time and equipment for incorporation.

Herbicides labeled for surface application may cause phytotoxicity to melons if incorporated, however.

Do not use herbicides that are not labeled for use in Florida. Use of unregistered materials can result in destruction of the crop, a fine or both. Use of herbicides with pending labels can also delay or jeopardize subsequent registrations.

The EPA has recently defined for tolerance purposes what crops may be included under certain general commodity names. The general term "melon" on a label includes the specific commodities: muskmelons, including hybrids and/or varieties of Cucumis melo (including true cantaloupe, cantaloupe, casaba, Santa Claus melon, crenshaw melon, honeydew melon, honey balls, Persian melon, golden pershaw melon, mango melon, pineapple melon, snake melon); and watermelons, including hybrids and/or varieties of Citrullus spp.

Muskmelons: includes hybrids and/or varieties of Cucumis melo (including true cantaloupes, cantaloupe, casaba, Santa Claus melon, crenshaw melon, honeydew melon, honey balls, Persian melon, golden pershaw melon, mango melon, pineapple melon, snake melon).

The term "Summer squash" includes fruits of the gourd (Cucurbitaceae) family that are consumed when immature, 100 percent of the fruit is edible either cooked or raw, once picked it cannot be stored, has a soft rind which is easily penetrated, and if seeds were harvested they would not germinate; e.g. Cucurbita pepo (ie. crookneck squash, straightneck squash, scallop squash, and vegetable marrow); Laginaria spp (ie. spaghetti squash, hyotan, cucuzza); Luffa spp. (ie. hechima, Chinese okra); Memordica spp. (ie. bitter melon, balsam pear, balsam apple, Chinese cucumber); and other varieties and/or hybrids of these.

Herbicides must be applied at exactly the correct rate and time to selectively control weed growth in a vegetable crop. Obtain consistent results by reading the herbicide label and other information about the proper application and timing of each herbicide. To avoid confusion between commercial formulations, suggested rates listed in Table 1 are stated as pounds active ingredient per acre (lbs. ai./acre). Read and follow all label directions.

 

Tables

Table 1. Chemical weed controls: cucurbit crops (muskmelons, cucumbers, squash, watermelon).

 

Herbicide	Labeled Crops	Time of Application to Crop	Rate (lbs. ai./acre)
			Mineral	Muck
Bensulide (Prefar 4E)	Cucurbit vegetable group: cucumbers, melons, squash (summer and winter), pumpkins, edible gourds, bitter melon	Preplant incorporated, Preemergence	5.0 - 6.0	----
Remarks: Controls germinating grasses. Incorporate 1 to 2 inches. Note precautions about reapplying within 12 months and planting non-registered crops within 18 months. Label states control of crabgrass, foxtail, goosegrass, fall panicum and sprangletop.
Bensulide + Naptalam (Prefar 4E + Alanap)	Cantaloupes, muskmelons, cucumbers, watermelons	Preplant or Preemergence	5.0 (Bensulide) + 3.0-4.0 (Naptalam)	----
Remarks: Combination (tank mix) will provide wider range of weed control than either material alone. Incorporate into the soil lightly (0.5 to 1.0 inch) with suitable equipment prior to planting or incorporate preemergent treatments with overhead irrigation. Follow all precautions on both labels.
Carfentrazone (Aim)	Cucurbit crop group (all)	Preplant Directed-hooded Row-middles	0.031	0.031
Remarks: Aim may be applied as a preplant burndown treatment and/or as a post-directed hooded application to row middles for the burndown of emerged broadleaf weeds. May be tank mixed with other registered herbicides. May be applied at up to 2 oz (0.031 lb ai). Use a quality spray adjuvant such as crop oil concentrate (coc) or non-ionic surfactant at recommended rates.
Clethodim (Select) (Arrow)	Cucurbits (cucumber, squash, melons and all commodities in crop group)	Postemergence	0.1 - 0.125	----
Remarks: Use Select for the control of annual and perennial grasses. Use a crop-oil concentrate at 1% v/v in the finished spray volume. Do not apply more than 8 fl. oz. product/A per application. Do not apply within 14 days of harvest.
Clomozone (Command 3 ME)	Summer squash Winter squash	Preemergence Preemergence Row Middles	0.15 0.25 - 0.75 0.75	----
Remarks: Labeled rate for summer squash if 0.25 lb a.i. Bleaching has been seen under adverse conditions at this rate. Suggest use as tank mix to increase efficacy. May be applied to winter squash and processing pumpkins. See label for varieties and cultivars where application is prohibited. Do not use on Jack-O-Lantern type pumpkins. May be used on processing type varieties. Read disclaimer on the label before use.
DCPA (Dacthal W-75) (Dacthal 6F)	Seeded melons: cantaloupe, honeydew, watermelon; cucumber; squash (summer, winter)	Early postemergence	6 - 8	----
Remarks: Apply only when plants have 4 to 5 true leaves and are well established and when growing conditions are favorable for good plant growth. Does not control emerged weeds. If weeds have emerged, cultivate prior to application. Do not incorporate.
Ethalfluralin + Clomozone (Strategy)	Cucumber, melons, watermelons, squash, pumpkins	Preemergence Post-directed	2 - 3 pints	----
Remarks: Strategy is a premix of ethalfluralin and clomozone at 1.5 + 0.5 lbs/gal. Apply 2-3 pints product post seeding to surface prior to crop and weed emergence. Must be applied no later than 2 days after seeding. Soil incorporate with overhead irrigation at 1/2 inch or with a rain(s) at no less than 2 inches within 5 days. Excessive rains or irrigation may cause injury. For furrow irrigation where no rainfall is received, a shallow cultivation may be used to activate the herbicides. Do not apply before transplanting. Do not apply under row covers, hot caps, or polyethylene mulches. May be applied as a post-directed spray to row middles after crop emergence or transplanting. Do not apply over plants. The premix controls a large number of grasses and broadleaf weeds.
Glyphosate (Roundup, Durango, Touchdown, Glyphomax)	Cucurbit Crops	Chemical fallow Preplant, pre emergence, Pre transplant	0.3 - 1.0	----
Remarks: Roundup, Glyphomax and Touchdown have several formulations. Check the label of each for specific labeling directions.
Halosulfuron (Sandea)	Cucumber, cantaloupe, honeydew and crenshaw melons	Preemergence, Postemergence Row middles	0.024	----
Remarks: Apply uniformly at 1/2 oz. product with ground equipment in a minimum of 15 gallons of water per acre. For postemergence applications, apply after the crop has reached the 2 true leaf stage, but before flowering. Use a non ionic surfactant for postemergence applications. May be used for row middle treatments at up to 1 oz. product. Controls actively growing nutsedge species best post. Do not apply within 30 days of harvest for cucumber and 57 days for the melon subgroup.
Halosulfuron (Sandea)	Cucurbit vegetables including watermelon, squash, pumpkins, gourds, etc.	Preplant Pretransplant Row middles	0.024 - 0.048	----
Remarks: May be applied as a preplant or pretransplant application to bare ground or mulch grown cucurbit vegetables at 1/2 oz product for the suppression of nutsedges and the control of listed broadleaf weeds. May be applied between rows for the control of emerged nutsedges and labeled broadleaf weeds at 1/2 to 1 oz product. Use a non ionic surfactant in the spray mix. Check the label for phi limitations.
Naptalam (Alanap-L)	Cantaloupes, cucumbers, watermelons	Preemergence, Preplant	3.0 - 4.0	----
Remarks: Apply within 48 hours of seeding. Apply preemergence to weeds and incorporate with overhead irrigation. Label states control of germinating annuals such as lambsquarter, ragweed, purslane, cocklebur, white mustard, shepherdspurse, redroot pigweed, hairy galingosa and carpetweed.
Naptalam (Alanap-L)	Cantaloupes, cucumbers, watermelons	Postemergence, Posttransplant	3.0 - 4.0	----
Remarks: Apply 1 month after planting when vines are starting to run but before weeds have emerged or immediately after transplanting. Do not use when plants are under stress due to weather conditions. Do not tank mix with crop oil or adjuvants. Phytotoxicity may occur.
Paraquat (Gramoxone Inteon) (Firestorm)	Watermelon, squash, pumpkin, cantaloupe, muskmelon, cucumber	Preplant or Preemergence	0.63 - 0.94	----
Remarks: Controls emerged weeds only. Apply prior, during or after planting, but before crop emerges. Use a non-ionic spreader.
Paraquat (Gramoxone Inteon)	Melons	Postemergence directed spray	0.48 - 0.93	----
Remarks: Controls emerged weeds only. Apply 1.0 to 3.0 pts. per sprayed acre with ground equipment directing spray between the rows and use shields to prevent spray contact with the crop plants. Add a non-ionic surfactant at 8 fl. oz. per 100 gals. of spray mix. Do not apply more than 3 times per season.
Pelargonic Acid (Scythe)	Cucurbits (melons; cucumber, gourd, pumpkin, squash, muskmelon and watermelon)	Preplant Preemergence Directed-Shielded	3 - 10% v/v	3 - 10% v/v
Remarks: Product is a contact, non-selective, foliar applied herbicide. There is no residual activity. May be tank mixed with soil residual compounds. Consult the label for rates and other information.
Sethoxydim (Poast)	Cucurbits: all	Postemergence	0.188 - 0.28	----
Remarks: Controls actively growing grass weeds. A total of 3 pts. product per acre may be applied in one season. Do not apply within 14 days of harvest. Apply in 5 to 20 gals. of water adding 2 pts. of crop oil concentrate per acre. Unsatisfactory results may occur if applied to grasses under stress. Use 0.188 lb. ai. (1 pt.) on seedling grasses and up to 0.28 lb. ai. (1.5 pts.) on perennial grasses emerging from rhizomes, etc. Consult label for grass species and growth stage for best control.
Terbacil (Sinbar)	Watermelon	Preemergence Pretransplant Row Middles	0.1-0.2	----
Remarks: For watermelon only. Apply 2 to 4 oz product (0.1-0.2 lb ai) to seeded or transplanted watermelon preemergence after planting to seeded and pretransplanting to transplanted watermelon. May be applied under mulch and to row middles. Controls many annual broadleaf weeds.

 

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Footnotes

1. This document is HS190, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Last revision date: October 2006. Please visit the EDIS Website at http://edis.ifas.ufl.edu.

2. William M. Stall, professor, Horticultural Sciences Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

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