Crop Profile for Watermelons in Texas

General Production Information

• Rank Nationally: Texas is the Nations number one producer of commercial watermelons. In some years, Florida will be number one in cash receipts. Texas generally always leads in acreage.
• States Contribution to Total Us Production: Texas produces about 20% of the US watermelons.
• Yearly Production: Texas plants from 50,000 to 60,000 acres of commercial watermelons per year, with cash receipts of approximately 50 million dollars. An unknown quantity of melons (people who do not ship) is sold from roadside stands and from trucks along the roadside. Watermelons, along with a number of other vegetable crops, are an important source of supplemental income in many areas of Texas.

Production Inputs:

• Nitrogen 40 lbs. A, Phosphate 60 lbs/A, total fertilizer cost $32.00
• Seeding rate 3 lb/A at $20/pound
• Herbicide Cost $51/A, Insecticide Cost $23/A, Fungicide Cost $32/A, Application Cost $4.00/A
• Pollination Expense $30/A
• Harvest Expense $3.50/A
• Plastic mulch $75-275/A depending upon plastic used
• Machinery labor cost $18/A, other labor cost $65/A
• Variable cost - Irrigated, South Texas $1071.94 (drip tape ca. $225/A)
• Variable cost - Dryland, South Texas $748.94
• Fixed Cost - Irrigated, South Texas $151.55
• Fixed Cost - Dryland, South Texas $78.42

Crop Destination:

• Fresh market - One 100 percent (100%).

Production Regions:

The defining of agricultural production regions in Texas is difficult. However, for small acreage crops there are some fairly definitive concentrations of production that are commonly accepted, with the boundaries often the point of contention. Watermelons are grown in nearly half the counties in Texas. The map listed here attempts to provide readers with some notion of these different geographical cropping areas. Watermelons are commercially grown in regions 1, 3, 4, 6, and nine(9). The top five watermelon producing counties are Hidalgo, Brooks, Knox, Gaines and Wood.

Watermelons are an annual crop in Texas. Harvest starts in early May in the Lower Rio Grande Valley(South Texas), June in the area west of San Antonio (Winter Garden), June-July in East Texas, late summer/fall in the Cross Timbers/DeLeon area, and in September and October in the High Plains. Eighty percent of Texas production is marketed in June, July, and August. The optimum marketing window is mid June-mid July.

Each of the Texas production regions will often have unique pest problems. Diseases are a good example. Anthracnose and gummy stem blight are important problems in northern areas of the state but are generally not considered treatable conditions in South Texas and the Winter Garden.

Varieties:

Open pollinated includes: All Sweet and Jubilee II. About 65 percent of the Texas commercial watermelon production is hybrid, 20 percent is open pollinated and 15 percent is seedless.

Soil Preference::

Deep, well-drained, light textured soil having a pH range of 5.5 - 8.0 (optimum 6.5 - 7.0). Does not tolerate heavy soils.

Optimum Growing Conditions:

Bright, hot days (80 - 95°F) and warm nights (60 - 70°F). Cooler temperatures and excessive rainfall will slow watermelon growth and maturity. Overcast, cloudy and/or rainy weather reduces sugars (fruit quality). In Texas, a 3-year rotation is recommended for watermelons to reduce the incidence of fusarium.

Establishment Methods:

• Direct seeded or transplants often on plastic mulch covered raised beds.
• Optimum time = When all danger of frost has passed and/or soil seed zone temperature exceeds 70° F.
• Seeding rate/A = 1 - 3 lbs. Seed/oz = 300 - 600.
• Seeding depth = 3/4 - 1"
• Seeding spacing = 3' in-row on 6' beds (irrigated); 5' in-row 8 - 10' beds (dry land).

Fertility/Fertilization:

Rates presented as actual lbs./A N, P₂O₅ and K₂O (base actual rates on soil test results). Generalized rate lbs./ A: 80 - 80 - 80, N - 40 - 90 lbs.; 0 - 50 lbs. preplant broadcast incorporated or split band 4" deep and 4 - 6' on either side of seed row @ planting + 20 - 30 lbs. side dressed three weeks after emergence; under high rainfall, and additional 20 lbs. may be required @ vining (side dress in split bands or through fertigation). P - 40 - 80 lbs; banded 3 - 4" below seed @ planting or near the level of the transplant root base. K - 40 - 80 lbs; if needed, applied with preplant N. Starter solution (transplants) = approx. 8 oz. of high phosphate starter solution/plant at field setting.

Water/Irrigation:

10 - 15"/season. Steady moisture supply (1 - 2" every 10 - 14 days) required, stop irrigation approx. 10 - 14 days prior to anticipated maturity (onset of flesh color). Key stages = establishment and fruit set. Drip irrigation has lead to dramatic yield increases in some parts of Texas.

Pollination:

Watermelons have separate male and female flowers and a narrow pollination window, generally only a few hours. This makes timely mechanical movement of pollen between flowers very important melon production practice. Because of this, many watermelon producers in Texas contract their pollination needs, most often with a commercial honey bee operation. One hive of bees per acre of watermelons is often adequate for pollination and the importance of this augmentation increases as the field size increases. Smaller operators with only a few acres will tend to depend entirely on naturally occurring pollinators. There are many other insects that are capable of pollinating watermelons. However, their occurrence may be limited, particularly in larger fields. In watermelons the time from flower to harvest is 30-45 days.

Worker Considerations:

Watermelon production becomes more labor intensive as the level of other inputs increases. At planting 1-3 workers are generally needed to accomplish most chores. This will increase at harvest since the crop is removed from the field in a very short period of time. Small, direct seeded plantings grown for the roadside market by a single operator will have a smaller amount of labor investment than the larger commercial settings. Melons grown from transplants under plastic mulch require more hand labor to get them established than a direct seeded crop, however these workers will generally not be exposed to treated seed. The irrigation tape often used to supply water to melons is laid down prior to planting and requires little maintenance.

Harvest is by hand. The smaller operators will generally handle melons at least twice during harvest. However, larger operators will pack directly to shipping crates in the field. Once loaded, shipping crates are handled by moving equipment and the melons will be sold directly out of the crate at retail outlets or unloaded by market personnel. Most pesticide applications will be by ground equipment, particularly with smaller operations. Late season treatments will generally be by air to avoid vine damage. Some hand hoeing occurs early in the season for weed control and thinning.

The Texas Agricultural Extension Service Insect Control Guide for Commercial vegetables, B-1305, lists a number of insect pests of melons. These include aphids, cucumber beetles, cutworms, cabbage looper, leaf hoppers, leaf miners, melon worms, pickleworms, mites, squashbugs, squashvine borers, and flea beetles. Key pests are cucumber beetles, aphids, and squash bugs. The following provides information on the more common insect pest of Texas watermelons.

Aphids are often mid to late season pests of Texas watermelons where damage results from the aphids' honey dew secretions. Since most watermelons are taken directly from the field to market, the honey dew, a sticky sweet substance, causes undesirable appearance for market. Aphids have also been indicated as transmitting certain mosaic viruses that attack watermelons. Feeding is on the underside of leaves, causing cupping and distortion. Warm humid weather coupled with vigorous, well-fertilized vines are conducive for aphid development. Scouting is an effective management tool where five aphids per leaf signals a damaging population. Beneficial insects such as lady beetles and lacewings can reduce aphid numbers and limit the number of required insecticide applications.

Cucumber Beetles: Cucumber beetles are generally only a problem to young watermelon plants. When the crop is first becoming established, these beetles will feed on young tender stems, leaves and shoots. Once vines are older and more dense, beetle damage can be tolerated. Cucumber beetles are green, oblong-oval Coleoptera that are about 5 mm long. Females lay oval, orange-yellow eggs in the soil in clusters of 25 to 50 on the undersides of host plant leaves. The beetle larvae are about 10 mm long and have a yellow-white, somewhat wrinkled body with three pairs of brownish legs near the head. Pupae are white, tinged with yellow and six to 8 mm long. Overwintering is in fence rows and surrounding fields.

Squash Bugs: Squash bug adults and nymphs feed on plant stems and leaves, often near the base of the plant. Damage occurs when unusually large populations are on the melons. Damaged leaves appear grayish and may wilt and die. Adults are brownish gray to dark gray bugs about 5/8 inch long and as nymphs have a green abdomen with crimson head. Eggs are laid in clusters, often on the top of leaves, but developing immatures generally are found underneath. Squash bugs transmit anasa wilt to watermelons. Synthetic pyrethroid insecticides used for squash bug control can cause late season aphid population increases.

Whiteflies: Whiteflies feed by sucking plant juices from host plants and heavy feeding can cause mottling or yellowing of the leaves. Adult whiteflies are about 1/16 inch long and have four wings along each side of the body that are covered with a white waxy powder. Immatures or nymphs are light green, oval and about the size of a pinhead. Whitefly adults secrete honeydew, a sweet sticky substance, that often, because of being a medium for smutty mold, will turn black and blemish fruit.

Watermelon Insect Control

Chemical Alternatives for Major Watermelon Insect Pests

Minor Use Request: (IR4 Pipeline)

• cyfluthrin + Tebupirimphos - Soil Insects
• bifenthrin - Squash Bug, Tarnish Plantbug
• clofentezine - Insects, Mites
• zeta-cypermethrin - Squash Bugs
• thiamethoxam - Soil Insects
• abamectin - Mites, Leafminers
• milbemectin - Spider Mites
• permethrin - Leafminer, Borer, Aphid, Cucumber Beetle, Whitefly
• pirimicarb - aphids

Weeds

Weeds are a constant problem in Texas watermelons. Plastic mulch has become an important tool in watermelon weed management, as well as water conservation, but weed control is essential to prevent mulch damage. Annual broadleaf weeds, annual grasses and perennial grasses are the targets of herbicide applications where timing and the understanding of weed life cycles are essential elements of successful control. Application timings are preplant or preemergence, early postemergence and postemergence (post directed).

Weeds that get a lot attention in watermelons include the nutsedges (generally because of damage caused to plastic mulch), pigweed, purslane, johnsongrass and Texas panicum. Management recommendations include: spot treating, hand hoeing or cultivating during a fallow season; cover crops in the off season, keeping fence rows, roadways, etc., clean; cleaning equipment before moving from field to field (to remove disease spores and weeds); and cultivation.

Watermelon Weed Control *

*National Agricultural Statistics 1996: http://usda.mannlib.cornell.edu/reports/nassr

Other registered herbicides for watermelons include: halosulfuron (Sandea) - preemergence; naptalam (Alanap) - postemergence; paraquat (Gramoxone) - preplant/preemergence; bensulide (Prefar) - preplant/preemergence; and glyposate (Round-Up).

Minor Use Request: ( In IR4 Pipeline)

• dimethenamid-P - weeds
• diquat - grass, broadleaf weeds
• clomazone - annual grasses & broadleaf weeds
• sulfentrazone - weeds
• clethodim - annual, perennial grasses
• terbacil - weeds & grassespPyrithiobac - broadleaf & grassy weeds
• thiazopyr - grassy & broadleaf weeds

Gummy Stem Blight (Didymella bryoniae): Gummy stem blight (GSB) is one of the most important diseases of Texas watermelons. Expressed in warm wet weather (the optimal temperature is 74F) symptoms include round, black, wrinkled spots on leaves and sunken dark areas on stems. A gummy brown material will ooze from older stems in the later stages of disease development. Disease development begins at the center of the plant and progresses outward. On the fruit, lesions appear as small, water soaked areas which eventually enlarge to an indefinite size. This fungus overwinters in infected plant debris in the soil and on seed. Cultural control would include suggestions to not disturb vines that are wet from dew or rain.

Anthracnose (Colletotrich orbiculare): Anthracnose is a consistent watermelon disease in East Texas and occasionally a problem more to the northeast. Anthracnose can completely kill vines before fruit matures, and will cause lesions on the fruit. The disease symptoms include irregular, brown to black, dry leaf spots, eventually causing the leaf to shrivel up and die. On the fruit, sunken, circular to irregular lesions occur from pinpoint size to one inch or more in diameter. Elongate stem and petiole lesions occur. Spores of the fungus are produced on lesions that may rapidly spread the infection following rainy weather. The fungus overwinters in decaying vines and on seed from diseased fruit. Infected fruits are often ruined in the field or lost to decay in transit.

Powdery Mildew: Two fungi are responsible for the powdery mildew disease, Spaerotheca fuliginea race two and Erysiphe cichoracearum. These quickly spreading fungi first appear as a white to gray, dusty material on the upper leaf surface and subsequently spread to cover the entire surface. Once a leaf becomes covered by powdery mildew it will die, eventually becoming dry and brittle. These diseases develop on older leaves and because of this tend to not be a consistent problem in Texas melons.

Wilt (Fusarium oxysporium): Wilt fungi are soil borne and enter the plants through the roots. Early disease symptoms are a brown discoloration inside roots and stems which leads to a plant vascular system breakdown and plants wilt, then die soon after symptoms are observed. Foliage of infected plants first turns yellow, which indicates the presence of Fusarium. Crop rotation is the best control method, often requiring intervals as long five years between plantings.

Downy Mildew (Pseudoperonospora cubenis) This disease first appears as large brown blotches on the upper surface of leaves and can rapidly defoliate vines. Stems and fruit are not affected. Downy Mildew development is favored by cool, wet nights, and warm humid days. It is mainly important in late-season (fall) production possibly because it does not overwinter well but moves in from tropical areas. The key to effective chemical treatments is early disease detection and regular preventive applications. Cultural control includes resistant varieties, isolating fields and reducing plant density to promote more open canopies.

Cercosphora Leaf Spot (Cercospora sp.): This disease causes small leaf spots that can cause a defoliation of vines under severe disease pressure. Airborne movement of spores is important for introducing the pathogen. The irregular leaf spots have a yellow halo and a dark-brown center which first appear on the oldest leaves. Damage is not only from defoliation, which can restrict fruit development, but increased exposure of melons to the sun resulting in scalding. Cercospora leaf spot is the most prevalent foliar disease of watermelon in many parts of Texas but it is not usually a serious problem. Because heavy infection can lead to defoliation, chemical control is often advised, particularly in south Texas.

Alternaria Leaf Blight (Alternaria cucumerina): This fungus overwinters on plant debris from the previous crop. The disease manifestation is similar to Cercospora, affecting older leaves first and progressing to the newer leaves, shoots and runners. Alternaria lesions resemble a target with a lighter area encircling a dark spot. A minimum of two years rotation is recommended as a cultural management practice for this organism.

Other Watermelon Diseases: Other diseases which would be considered occasional pests of Texas watermelons include: White mold (Sclerotinia sclerotiorum), Rhizoctonia solani, Damping off (Pythium) which is managed with seed treatments, bacterial fruit blotch (Acidivorax avenae), and yellow vine. The squash leaf curl virus, a common disease of fall watermelons, is transmitted by whiteflies and can be managed by controlling the whiteflies. Other viruses include the watermelon mosaic virus, papaya ringspot virus and the tobacco ringspot virus.

Chemical Control of Watermelon Diseases: There are several chemicals listed below that are used for disease control in watermelons. Most, when applied, are efficacious against more than one pest. This broad spectrum characteristic influences the use of a material since the more diseases likely controlled with a single application, the more likely it will be the chemical of choice. Use information is complicated by the fact that many compounds are used in combination or 'tank mix' with other fungicides.

Watermelon Disease Control*

* Many fungicides are applied in combination with other fungicides to broaden an application's spectrum of control.

Watermelon Disease Control Alternatives

Resistance Management: Combination of chemicals is often recommended to help prevent disease resistance. For instance, menfanoxam (Ridomil Gold) can be used in combination with protectant fungicides such as Mancozeb or chlorothalonil to help prevent the emergence of resistant strains. Alternative chemical applications are suggested for new fungicides such as the strobilurins (Quadris/Cabrio) to prevent disease resistant development.

Minor Use Request: ( In IR4 Pipeline)

• famoxadone + cymoxanil - downy mildew
• fludioxonil - monosporascus cannonballus
• tebuconazole - powdery mildew
• difenoconazole - gummy stem blight

Contacts

Prepared By:

Rodney L. Holloway and Kent D. Hall
Extension Specialist and Extension Associate Respectively

Rodney L. Holloway
Extension Specialist
Texas Cooperative Extension
College Station, Texas 77843
rholloway@tamu.edu

Frank Dainello
Extension Horticulturist
Texas Cooperative Extension
College Station, Texas
f-dainello@tamu.edu

Juan Anciso
Extension Horticulturist
Texas Cooperative Extension
Weslaco, Texas
j-anciso@tamu.edu

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2. Black, Mark. Et al. 1998. Vegetable and Herb Disease Control Products for Texas. Texas Plant Disease Handbook. Texas Agricultural Extension Service E10, 86pp. http://agpublications.tamu.edu/pubs/eplant/ 1-98.

3. Dainello, Frank. 1996. Texas Commercial Vegetable Production Guide. Texas Agricultural Extension Service Publication. 129 pp.
4. Dainello, Frank. 1996. Weed Control in Vegetable, Fruit and Nut Crops. Texas Agricultural Extension Service B-5022. 22pp.

5. National Agricultural Pesticide Impact Assessment Program Web Site: http://ipmwww.ncsu.edu/opmppiap/.
6. Texas A&M University Research and Extension Center at Weslaco Web Site: http://primera.tamu.edu/
7. USDA/National Agricultural Statistics Service. 1997. Texas Agricultural Statistics. 158 pp.http://usda.mannlib.cornell.edu/reports/nassr.