Alabama: Cotton Bollworms, Soybean Loopers Coming on Strong

    Alabama row crop farmers need to be actively scouting their crops for two perennial pests, cotton bollworms and soybean loopers. Dr. Tim Reed, an entomologist with the Alabama Cooperative Extension System says traps are capturing increased numbers of adults of both species.

    “We are seeing more cotton bollworm moths in pheromone traps in some central and south Alabama counties in Alabama than we have seen in recent years,” said Reed. “Soybean looper moths have also been trapped in significant numbers at two locations.

    “It’s important that farmers scout their cotton and soybean fields closely.”

    While most commonly known as the cotton bollworm, the same pest is also known as corn earworm and soybean podworm. No matter the name, it can do significant damage to crops.

    Cotton Bollworms–Numbers Building

    He added the number of cotton bollworm (CBW) moths collected in pheromone-baited traps have increased significantly at some trapping sites since June 20. Alabama Extension entomologists have traps established at multiple sites across the state to monitor the presence of a number of crop pests.

    Reed says that during the first week of July CBW moth trap catches were extremely high in both Baldwin and Elmore counties. In addition, CBW moths were commonly seen in cotton test plots at Auburn University’s Prattville research station during the first and second week of July.

    Cotton bollworms remain in the larval stage for about two weeks and feed primarily on the crop’s fruiting bodies, i.e. cotton bolls, corn ears or soybean pods. They will do about 80 percent of their feeding in the last four to five days of the larval stage which lasts about 2 weeks. Cotton bollworms then drop to the ground and pupate in the soil, before emerging as an adult moth. Reed says it takes about a month for the insects to develop from eggs into adults.

    “Conventional and, to a lesser degree, most Phytogen cotton varieties are susceptible to yield loss from CBW larvae,” he said. “CBW moths could also be laying eggs in reproductive-stage soybeans. Extremely high temperatures will allow eggs to hatch in less than 72 hours.”

    Soybean Looper Numbers Building

    If increased numbers of cotton bollworm moths weren’t bad enough news for farmers, Reed says that recent trap counts indicate that soybean loopers (SBL) are present this year in large numbers as well.

    “We have seen counts really grow over the last month in our Baldwin County traps,” he said. “High SBL moth counts have also been seen in traps in Elmore county.

    “The large number of moths collected in Baldwin County during early July could indicate that SBL infestations in Gulf Coast soybeans might begin earlier this year than normal,” said Reed. Defoliation levels in soybeans along the Gulf Coast normally reach the 10  to 20 percent range as early as the first week of August.

    Unlike CBW larvae, soybean looper larvae feed primarily on foliage.   SBL larvae will normally start feeding in the lower half of the plant canopy and move upward over time.

    “Early on, farmers will see leaves with a window pane effect. The SBL larvae eat only the green portion of the leaf leaving behind the transparent cuticle layer. As larvae mature, they become more aggressive feeders and once soybean loopers begin feeding on the upper canopy, they can soon consume more than 50 percent of the foliage when numbers are high.”

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