Tuesday, June 20, 2017

Texas High Plains Cotton: Keep an Eye for Grasshoppers

Suhas Vyavhare, Extension Cotton Entomologist, Texas A&M AgriLife Extension Service

Early planted cotton with adequate soil moisture should now be safe from thrips damage. However, fields with less than 4-5 true leaves/plant should be continued to scout for thrips. Normally, once we are past thrips season, I shift my attention towards cotton fleahopper. This year, however, grasshoppers can come into play early in the season. Last year we experienced grasshopper outbreaks in spots causing severe stand reduction and defoliation on larger plants. With the extended spell of hot and dry conditions on the Southern High Plains, my antennae are already wiggling for grasshoppers.
Grasshopper populations can increase dramatically under low rainfall and dry weather condition and be very destructive to young cotton. Grasshoppers have a high reproductive capacity. The female can lay up to 400 eggs in variety of crops as well as non-crop areas including ditches, fence rows, grassy fields, along roadsides and in pasture areas. Both the nymphs (immatures) and adults feed voraciously on plant foliage. When wild grasses and other plants become dry, the grasshoppers migrate to crop plants. Margins of fields are usually impacted first. Typically, grasshoppers feed on cotton foliage without causing significant crop injury. However, during the outbreak periods, they can become very destructive. Large numbers of grasshoppers are capable of completely destroying stands of seedling cotton, especially around field edges.

Fields with a known history of grasshopper outbreaks can be protected using mechanical and cultural methods (tillage and weed control) that target eliminating egg-laying sites and weedy hosts around the crop field. Producers need to watch out for grasshoppers and begin control measures if needed while they are in the immature stages as adults sometime can be hard to kill with insecticide applications.
Results from 2016 grasshopper insecticide performance trial can be found at: