Source: Dominic Reisig, NCSU COOPERATIVE EXTENSION, 7/12/19


As we have seen in previous years from monitoring corn, Bt resistance is on the rise. They also are more numerous than 2018 in corn and I expect our major July-August flight to arrive a bit earlier than usual. Bollworms that are produced in Bt corn are adapted to survive on Bt cotton. What we have done in cotton prior to this point in the season may determine how many bollworms we have to contend with. If we can avoid spraying insecticides prior to a bollworm flight (except selective ones), we can preserve some of the natural enemies that help us ward off bollworm infestations.

Cotton growers should enter bollworm season with a plan and be prepared to spray Bt cotton if they want to preserve yield. Bollgard II, TwinLink, and WideStrike are most at risk. Bollgard 3, TwinLink Plus, and WideStrike 3 varieties will only need to be sprayed under the most extreme pressure situations. There are two strategies that growers should take. While both have benefits and costs, both rely heavily on good scouting for proper implementation.

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