By ANDREA McCANN
Indiana Correspondent

VINCENNES, Ind. — A new polycarbonate greenhouse with computerized temperature control will provide an appropriate climate year-round for watermelon disease research at the Southwest Purdue Agricultural Center (SWPAC).

The greenhouse, which measures 22-feet by 24-feet, was paid for in large part by members of the Illiana Watermelon Assoc., who’ll benefit from the research.

“The Illiana Watermelon Association auctioned loads of watermelons to raise the money that paid for the greenhouse,” said Purdue University Extension Plant Pathologist Dan Egel. “It was a year ago (in) March. I’m excited they did that, because it means they’re solidly behind this program.”

Among the plant diseases Egel studies in the Southwest Purdue Ag Program (SWPAP) is mature watermelon vine decline (MWVD). The program received a grant from the Indiana Commissioner of Agriculture to determine the cause of MWVD and ways to manage it in commercial watermelon fields.

However, Egel said, most of his research is done in the field, and MWVD hasn’t shown up for a number of years. That makes it difficult to study unless he can duplicate it in a greenhouse setting. But the old polyethylene houses are too hot in summer and too cold in winter. They’re used primarily to raise transplants for field plots in the spring.

The new polycarbonate greenhouse has double-layered walls with air cells between layers. The back wall sports a large cooling pad, and the front has a fan and a propane heater. A control box in a back corner allows the interior climate to be adjusted.

“Hopefully it’ll have some insulation properties,” Egel said.
He explained that the cooling system is evaporative. Water drips down through a cardboard pad, which sets in front of a large shutter. When the shutter is open and the fan is on in the front of the greenhouse, air is sucked through the cooling pad and into the greenhouse. Through the control box, temperature settings for day and night can be set separately.

“Yesterday was the longest day of the year,” Egel said on Friday at an open house for the new greenhouse. “That’s gonna be different from December 21st, but I don’t have to tell it. It knows that.”

The plant pathologist said he expects to be able to raise at least 24 watermelon plants to maturity in 5-gallon buckets and hundreds of smaller potted plants in the greenhouse.

“I grow some in 5-gallon buckets to maturity so I can get a feel for diseases that affect plants in maturity,” he explained. “I grow them up, not out, so I have more space.”

MWVD, which used to be called Sudden Wilt, according to Egel, will be one of his focuses in the new greenhouse, because when it strikes, it can have a devastating effect. Mature vines suddenly die and cannot support their fruit. The fruit is then lost before it can be harvested.

“We haven’t seen it lately, but I can duplicate it in the greenhouse,” Egel said. “In 1999, 2000 and 2001, mature watermelon vine decline was a huge problem here. Since then, it’s been very little problem.”

Although it’s unknown exactly what causes the disease, Egel said it is known that it’s prevalent when there are heavy rains. He said roots begin to rot, and the vines die. By simulating the same environmental conditions in the greenhouse, he’ll be able to force the disease to occur so he can study it.

Currently, researchers believe watermelon is the only host for MWVD. They know it’s soil-borne – probably a fungus – and that water-saturated soils are associated with an increase in the severity of MWVD. Several soil fungi are being screened for possible roles in MWVD.

The new polycarbonate house will play a major role in MWVD research, and Egel said he wanted to have the open house to thank the growers who contributed and to permit everyone to walk through and see it. Illiana Watermelon Growers donated $20,672.40, which Egel said was almost exactly the cost of the greenhouse. Construction costs will add to that, he said, but the Purdue Department of Plant Pathology also has contributed to the project.

Illiana Watermelon Assoc. growers who contributed part of their 2006 crop to raise money for the structure are: Dexter Bloebaum, David Coates, Bob Ellermann, Larry Ellermann, Paul and Arlen Ellerman, Anita Field, Jay Halter, Leger and Son, Arnold Mack, Melon Acres, Mouzin Brothers Farms, Jim and John Stevens, Wabash Valley Growers, Kent Williams and Brad Wonning. The donated loads were purchased by Browning and Sons, Cato Foods, Indianapolis Fruit, Raymond Land and Dan Johnson.

The 220-acre SWPAC is located 1 mile north of Vincennes on U.S. 41. Besides Egel, there is also a horticultural specialist, an entomologist and an agronomist on staff at the center. Research and activities at SWPAC are “aimed at maintaining a safe, quality food supply and a healthy environment while supporting families and communities associated with the agricultural industry.” Information gained through research is passed on to growers and consumers in a variety of ways. Three of the researchers also teach courses at Vincennes University.

This farm news was published in the June 27, 2007 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.