From field to storage, entomologist investigates pest management strategies

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An LSU AgCenter entomologist sprays a rice field with insecticides. Photo by James Villegas. Below, Multiple sugarcane borer larvae are found in a rice stem. Growers who plant their rice late in the planting season can use seed treatments to control the borers. Photo by Tyler Musgrove.

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“Previously managing the rice water weevil was a challenge because the larvae are under the soil feeding on the roots, so they were difficult to target with foliar insecticides,” Wilson said. “With seed treatments they can impregnate the chemical onto the seed, and it’s taken up in the plant roots and leaves as the plants grow.”

Wilson is investigating ways to use these treated seeds efficiently and identify ways to provide the most return on the farmer’s investment.

He is also revisiting research that was done before seed treatment control — draining and drying fields.

“If you could dry down the soil and pull the water off to the point where the soil is cracking, that is supposed to kill them, but it’s often very difficult to get it that dry,” he said.

Rain and moisture levels can keep fields from completely drying out, so his research looks at what level of soil moisture is required for the infestations to continue.

“Essentially we want to know how dry is dry enough,” he said.

While the rice water weevil is the most ubiquitous and damaging pest in Louisiana rice, he is helping farmers control other insects, too.

“One of the things we’ve done recently is try and examine some of the more sporadic or less studied pests to see what influences the seed treatments are having on them,” he said.

Wilson’s research has shown that unless a grower plants late, the value of controlling stem borers with seed treatments is low. For growers who may get a late start because they also produce crawfish or a wet spring delayed planting, seed treatment will control the borers that infest late-planted fields.

Row rice presents a different set of insect challenges for farmers, Wilson said.

“When you remove the water from the system, that changes the dynamics,” he said. “In row rice, there are a number of other insects that are emerging as threats that were being controlled by the water, particularly the rice billbug.”

This insect feeds low on the stems and can reduce yields. Wilson has documented a 10-15% yield reduction in billbug-infested fields.

Wilson also has made progress in controlling the invasive apple snails, which have infested rice fields and crawfish ponds in southwest Louisiana. The snail’s impacts to rice overall have been minimal.

“Currently it’s a big problem on a small number of farms,” he said.

Most farmers are drill seeding rice, which doesn’t have standing water on it until three to four weeks after planting. “At that stage, the rice is no longer susceptible to snails,” said Wilson.

In water-seeded rice, the aquatic apple snail can become established in the field.

“We’ve seen where they ate every plant in the 50-acre field, and the grower had to replant,” he said.

The snail can be immensely detrimental to crawfish, which many rice farmers rotate with rice.

Wilson is looking at potential pesticides that are going to be effective against the snails but won’t harm the crawfish.

“We’re trying figure out not just what we can spray to kill them, but when will it be beneficial to spray to get some lasting control,” he said.

Other research in Wilson’s integrated pest management projects is determining the level of peck damage on rice from stink bugs. These bugs can cause discoloration, known as peck, on rice grains. He also is continuing work on insect infestations on stored rice.

After harvest, insects can get into the bins where rice is stored and feed on the grain. Wilson said there hasn’t been much research in this area particularly in rice and in Louisiana. Research on storage pests has mostly been conducted on corn and wheat in the Midwest.

The rice weevil, which Wilson notes is different than the rice water weevil, and the lesser grain borer are the two main pests in stored rice.

“We’ve seen that the varieties might differ tenfold in how quickly the infestations build up between the two different pests, but the varieties that are resistant to one pest aren’t necessarily the ones that are resistant to the other,” he said.

Wilson has conducted small-scale studies on applying insecticides directly to the grain as it goes into the grain bin and have seen positive results.

“We aren’t sure how well it will scale up in terms of getting the right coverage,” he said. “Developing this information into actual pest management strategies is going to be the next challenge.”

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Rice grains can be treated with insecticidal seed treatments. The blue rice has been treated with Dermacor X100, and the red was treated with CruiserMaxx.
11/21/2022 5:09:26 PM
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