Sept. 3, 2007

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LUBBOCK- Inquiring minds want to know. The supermarket headlines tell us so.

Inquiring Texas research minds want to know more about cotton fleahoppers - a tiny, sometimes obscure pest that can damage plants during their early growth.

"Fleahoppers are a threat to young cotton for about four weeks," said Dr. Megha Parajulee, Texas Agricultural Experiment Station entomologist based at Lubbock. "They feed on new plant growth, primarily the first small squares. This damage can delay plant maturity, leaving the crop open to damage from other pests later in the growing season."

But these tiny pests aren't all bad. After cotton reaches peak bloom, this tiny critter is considered a beneficial insect – living out its relatively short life as both a predator and prey species.

"Fleahoppers prey on bollworm eggs after peak bloom," Parajulee said. "They also serve as a food source for other predatory beneficial insects as the growing season progresses. But we really don't know much about this pest. We know it is only a cotton pest in Texas and Arkansas, but there is more we don't know."

For instance:

– Can cotton plants compensate for fruit/square loss caused by fleahoppers and still produce acceptable yields?

– What threshold of fleahopper numbers or feeding damage should trigger a chemical control?

– What pesticides work best against fleahoppers without damaging beneficial insects?

A three-year study begun in 2006 by Parajulee and other scientists at the Texas A&M University System Agricultural Research and Extension Center at Lubbock may provide answers to these questions.

"We raise fleahoppers here in our 'nursery' and place them on drip- and furrow-irrigated cotton plants/plots." Parajulee said. "We vary the number of fleahoppers, and we watch them closely through peak bloom to determine where they live and feed on the plants. This will help us develop effective scouting methods for this pest."

Plants in these fleahopper-infected plots are compared to those not seeded with fleahoppers (naturally-occurring insect populations) and to plants chemically treated for fleahopper damage.

"2006 was not a good year for our study. It was very hot and dry," Parajulee said. "Even so, we learned that cotton plants can compensate for fleahopper damage. These plants incurred up to 25 percent fruit loss from as many as three fleahoppers per plant and still produced almost 800 pounds of lint per acre.

"Their yield compared favorably to plants treated for fleahoppers, and untreated plants left to naturally-occurring insect populations." Parajulee hopes 2007 data from this study will help generate a fruit (square) loss treatement threshold. By 2008, the scientists hope to add specific chemical control tips to their arsenal of fleahopper knowledge.

Parajulee is also contributing to another study designed to survey fleahopper biology, behavior and movement statewide, and generate management recommendations for cotton producers.

That study began in 2007 and is led by Dr. Chris Sansone, Texas Cooperative Extension entomologist at San Angelo. Other contributors are Dr. Raul Medina, Experiment Station research entomologist at College Station; Dr. Charles Suh, U.S. Department of Agriculture Agricultural Research Service entomologist at College Station; John Westbrook, USDA Agricultural Research Service meteorologist at College Station; several Extension integrated pest management agents, and Apurba Barman, an entomology doctoral student at Texas A&M University.

"For many years, we entomologists have worked under the assumption that fleahoppers build up in wild host plants and then move into cotton prior to squaring," Parajulee said. "In the eastern part of Texas, fleahopper migration into cotton from wild host plants is pretty constant. Producers there can spray two to four times a season to control them.

"In the Rolling Plains, lack of rainfall limits wild host plants and makes fleahoppers an occasional cotton pest. Producers there rarely need more than one control treatment. On the High Plains, where we have an ocean of cotton and islands of wild host plants, it takes longer for fleahopper populations to build up to damaging levels. But once that level is reached, they can severely impact a lot of cotton by delaying fruiting."

The statewide survey will identify wild host plants that harbor fleahoppers, how and when this pest moves from host plants to cotton, and determine if fleahopper populations from wild host plants and cotton are biologically the same, he said.

"With this knowledge we can recommend cultural practices (plant/weed control), scouting methods, economic thresholds for treatment, and pesticides and application rates to help keep fleahoppers in check," Parajulee said.

Both studies are funded by Cotton Incorporated's Texas State Support Committee.