Research efforts between the Lower Southeast land-grant colleges of the University of Georgia, Clemson University and Auburn University continue to focus on thrips injury on early season cotton and how to avoid it.

“From an entomologist’s standpoint, thrips are one of the easiest insects we work with,” says Philip Roberts, University of Georgia Extension entomologist. “Infestations are usually very uniform, and thrips are very predictable pests if you plant your trials at the appropriate time. It’s easy to get data for thrips.”

Obviously, slow seedling growth results in increased injury from thrips feeding on the plant, says Roberts.  Preventive treatments used at planting could result in very consistent yield responses, whether with Temik or seed treatments, he says.

“If you’re looking for injury from thrips, it’s important to look at that newly expanded leaf. Thrips is a pest we almost take for granted.  But if we didn’t have such good tools to control thrips, we’d have a battle trying to manage them. When we have excessive thrips injury, we see an obvious stunting of plants,” says Roberts.

And wherever you see the above-ground stunting of cotton plants, you can be assured there’s a similar response below the ground, he says.

“In trials, we have dug plants in the field and cut and weighed the roots to get dry weights of the roots. We potted seedlings and came up with treatments where we could generate three levels of thrips damage — low, moderate and severe.

“At 14, 21 and 28 days after planting, we washed the roots and took dry weights of above-ground plant parts and below-ground parts. Where we had low thrips injury, we had much more root growth than with the moderate or severe thrips injury,” he reports.

Rapid root growth also is a very important consideration in a situation where there is nematode pressure, he adds.

“When we talk with our county Extension agents about thrips, I like for them to think in terms of risks. With the loss of Temik and the anticipated shortage of aldicarb this year, this will be an even more important topic for growers in the Southeast.”

Earliest planted cotton is where growers tend to see the highest thrips populations, says Roberts.

“Typically, we get to a point in the year to where thrips numbers crash based on planting date. Also, when we plant early, we usually have cooler temperatures.

“Anytime we have a slow-developing seedling, whether from cool temperatures, a low-vigor variety, herbicide injury or any plant stress that will delay seedling growth, that’s when thrips can punish us in terms of yield loss.”