If an ounce of prevention is worth a pound of cure, what is a pound or a ton of prevention worth? For High Plains cotton producers, the answer could be an entire field or an entire crop when bacterial blight rears its ugly head.
"Bacterial blight typically shows up on the High Plains in July and August," said Dr. Terry Wheeler, Texas Agricultural Experiment Station plant pathologist based at Lubbock. "The culprit is a bacteria that survives on plant debris littering the soil. Wet field conditions – for example, two to three rain showers in a month – triggers it.

"It spreads wildly, because the bacteria can be blown by the wind from field to field. The first symptoms are dark-colored leaf spots. It spreads across leaves, causing them to fall off. If it reaches the boll, it can infect and damage the seed inside. There are no seed or foliar treatments for it."

A major outbreak occurred on the High Plains in 1997. Damaging, but local, outbreaks occurred in 1998 and 1999, Wheeler said.

High Plains cotton farms typically range from a few hundred to a few thousand acres. An acre is roughly the size of a football field, minus the end zones. Dryland yields in this region range from one-half to one bale per acre, while irrigated acreage normally produces one and one-half to two 480-pound bales per acre.

An untreatable disease that takes out an acre of one-bale cotton could rob a producer of more than $200, given a market value of 50 cents per pound. Even a little bacterial blight in the region's 3.7 million cotton acres could have significant economic impact.

Widespread concern from cotton seed companies and producers led the Plains Cotton Growers, Inc., the state's leading cotton producer association, to fund the blight screening project from 2000 onwards.

"We raise our own bacterial blight inoculum in the lab here at the Lubbock research and extension center," Wheeler said.

It takes two days to raise enough blight inoculum in the lab to spray 10 acres. Research technician Michael Petty spends about one month spraying plots of cotton at several different locations.

"We start at the cotton nursery maintained by Dr. John Gannaway, Experiment Station cotton breeder at Lubbock," Wheeler said. "Then we branch out to nursery acreage owned by different seed companies.

"We mix the inoculum with a special sticking agent in a clean 50-gallon tank and apply it through large nozzles on a four-row sprayer mounted behind a tractor. It's a slow-speed application because we cover only about one acre with each 50-gallon tank mix."

Two to three weeks after each spray application, the researchers return to the field and rate the cotton plants for symptoms of bacterial blight.

Because the screen affects only a few leaves on each plant, and does not spread to other areas of the field, it has been very well received by seed companies, Wheeler said.

"When we finish a screen, we come out of the field with a resistance/tolerance rating for each variety," Wheeler said. "Then we share that information with the seed companies and producers. The screening project is a service component of our plant pathology research.

Research was used to develop this procedure, but now our time is spent executing the procedure for everyone's benefit.

"Bacterial blight is a 'sleeper' that we don't want to forget. We know it's out there, but we don't know when or where it might explode again.

Our goal is to get the seed companies the information they need to breed and select for better blight resistance as they develop new varieties. Prevention is our best protection."

Writer: Tim W. McAlavy