Seeking new countermeasures for insects that devastate potato crops

Video: Texas A&M AgriLife

Common insecticides are becoming less effective against the insects that spread zebra chip disease to potato crops, and scientists with Texas A&M AgriLife Research are looking for answers.

The potato psyllid is a tiny insect with sucking, piercing mouthparts that transmits zebra chip and can cause tremendous losses to potato producers.

Ada Szczepaniec, Texas A&M AgriLife Research entomologist in Amarillo, says many psyllids migrate from Mexico into the Rio Grande Valley. The aggressive use of neonicotinoid insecticides in Mexico has allowed psyllids to develop a resistance.

“It only takes a few psyllids to cause tremendous losses to a crop because they do not need to feed for a prolonged period of time to transmit the disease,” Szczepaniec said.

The disease causes the starches in the potato, when fried as a chip or a French fry, to harden and turn dark brown, causing the zebra chip pattern that makes the food product look unappealing and taste bitter, she said.

“We are trying to figure out is how to control the psyllids,” Szczepaniec said. “The biggest potato-producing region in Texas is of course the Rio Grande Valley. So some of these psyllids come up from Mexico into the valley and when the production of potatoes and tomatoes ends in the valley, they keep moving up north.”

Szczepaniec is collecting potato psyllids from all the major potato-producing regions of Texas and testing them in her greenhouse to see if they are still susceptible to neonicotinoid insecticides.

“We maintain these psyllid colonies on tomato plants and then expose plants to the insecticide as they would be treated in the field. We then move the immature psyllids onto the plants and measure their survival,” she said. “That allows us to figure out if they are still effectively suppressed by the insecticides. What we are looking for is close to 100 percent mortality.”

Szczepaniec said she will be testing other insecticides as well once it is determined which populations are no longer susceptible to the neonicotinoids.

“We want to figure out what producers can use if neonicotinoids are no longer effective in their region,” she said. “We will continue the testing and collection over several years in order to provide producers with customized combinations for their regions where we collected the psyllids and help them manage them successfully.”

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