By MINDY POEHL | Central Texas Edition

This cantaloupe has gummy stem disease, which forms brown spots on the fruit.

June 1, 2006 - Melons play an integral role in the farming of Comanche County. Comanche growers plant around 800 acres of melons annually, with a potential to earn $5,000 per acre.

“Starting in mid-June, our growers will ship a million pounds of watermelons a day,” said Bob Whitney, Comanche County Extension agent.

Texas is the nation’s number one producer of commercial watermelons and Texas produces nearly 20 percent of the watermelons in the United States, noted Tom Isakeit, Extension plant pathologist at Texas A&M University. 

Isakeit was one of the speakers at the Melon Production Tour that was held in Gustine on Tuesday, May 23.

“Watermelons are grown in nearly half the counties in Texas,” Isakeit said. “They are an annual crop in Texas, with 80 percent of the production marketed in June, July and August.”

The optimum growing conditions for watermelons consist of bright, hot days (80 - 95 degrees) and warm nights. Overcast and rainy weather reduces the sugars and the fruit quality. 

"The melons are grown in 50-60 days from the time the transplants are put in the ground," Whitney said. "The only way to do that is using plastic mulches, irrigation and good quality transplants."

Cantaloupes can tolerate heavier soils than other melons can. In Comanche, people begin planting cantaloupe in late March. A second planting is made two weeks after the first planting, and a third planting is made two weeks after that.

“Multiple plantings extend the harvest and marketing period,” Isakeit said.

Sucking insects that affect melons include sweet potato whiteflies, melon aphids, spider mites, western flower thrips, and squash bugs.

Melon aphids and spider mites tend to appear annually in Central Texas. Desiccation of plants occurs when the insects invade the crops. The plants become unthrifty and  nonproductive, and the fruit is unmarketable. Melon aphids build up rapidly and deposit considerable honeydew on leaves. “Adults and nymphs suck juices from leaves, sapping the plant’s energy and causing leaves to curl, become malformed and eventually die,” explained Isakeit. “A dark sooty mold grows on the honeydew these aphids excrete.”

Whitney added, “Since most watermelons are taken directly from the field to market, the honey dew, a sticky sweet substance, causes undesirable appearance for market.” 

An important aspect of this aphid damage is the spread of plant viruses. The viruses they spread cause more damage to the cantaloupe crop than the melon aphids alone. The attacked plants begin to lose color, fading from green to yellow and eventually turning reddish.  

Chewing insects that affect melons include serpentine leafminers and cabbage loopers.

Maggots of serpentine leafminers live by eating leaf tissue between the upper and lower  surfaces, leaving slender, white winding trails through the leaf's interior. Cabbage loopers are voracious feeders, which can strip foliage from infested plants in a short time. Often, when populations become crowded, a virus disease strikes, causing high larval mortality. 

Diseases in the melon fields include downy mildew, alternaria leafspot, gummy stem blight and powdery mildew.

Downy mildew infection produces lesions on the leaves. The lesions expand in a few days and the entire leaf may be dead. 

“Death of the leaves decreases photosynthetic capacity and exposes the  fruit to sun scald, which results in reductions in both quality and quantity of marketable yield,” explained Chris Sansone, Extension entomologist.

 Alternaria leaf spot only develops on the leaves. Severely infected leaves become yellow around brown lesions and then die. Heavily infected plants have fewer and smaller fruit.

Gummy stem blight infects leaves and stems, and is more prominent in the crown at soil level. Leaf symptoms begin with irregular spots that dry and drop out giving the lesion a ragged appearance.

“The most conspicuous phase of the disease is the brown exudation in the crown of  infected plants,” Sansone said. “Vine cankers are found near the soil line, producing a gummy brown ooze.”

Powdery mildew reduces yields by decreasing the size or number of fruit. Fruit quality can be reduced by sun scald and premature or incomplete ripening with resultant poor flavor.

Weeds are a constant problem in Texas watermelons. Plastic mulch has become an important tool in watermelon weed management. Weeds in watermelon fields include the nutsedges, pigweed, purslane, johnsongrass and Texas panicum. Management recommendations include spot treating, hand hoeing or cultivating during a fallow season; covering 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.