Performance of New and Existing Bt Cotton Technologies When Inundated with Heavy/Natural Populations of Bollworm In SC - 2010

Since 1996, single-gene (Cry1Ac) Bt technology (Bollgard®) has been available in cotton varieties planted in the USA.  In 2003, dual-gene (Cry1Ac and Cry2Ab) Bt cotton technology (Bollgard II®) was introduced by Monsanto, offering enhanced in-plant control of caterpillar pests, particularly bollworm.  As a result, applications of foliar-applied insecticides were further reduced, but not totally eliminated.  In 2005, an alternate dual-gene (Cry1Ac and Cry1F) Bt cotton technology (WideStrike®) was made available by Dow AgroSciences.  While varieties with Bollgard II® or WideStrike® technology provide very good control of caterpillar pests, they do not offer 100% control of bollworm.  Under extreme pressure from Helicoverpa zea, these technologies require supplemental applications of insecticide to avoid yield losses due to injury from the species.  A new arrangement of Bt genes (Cry1Ab and Cry2Ae) will be available in TwinLink® technology from Bayer CropScience within a few years.  Reported here are the results of separate evaluations of existing and promising Bt cotton technologies when inundated by natural infestations of bollworm.