Seasonal Occurrence of Lepidopteran Pest of Soybean and the Implications for the Natural Refuge

SEASONAL OCCURRENCE OF LEPIDOPTERAN PEST OF SOYBEAN AND THE IMPLICATIONS FOR THE NATURAL REFUGE

Nick Bateman

Angus Catchot

Jeff Gore

Fred Musser

Trent Irby

Mississippi State University

Starkville, Mississippi

 

Abstract

Dual gene Bt cotton was first introduced in 2003, and with this introduction of these dual gene cottons, the natural refuge system was implemented and took the place of a structured refuge system.  This system used the surrounding landscape as refuge for the cotton bollworm.  With the possibility of Bt soybean being introduced to the United States, the role soybean in the natural refuge needs to be evaluated.  Past research has shown that C4 plants play the largest role in the natural refuge, but soybean are also playing a role in the natural refuge. Surveys were conducted throughout Mississippi across early, normal, and late planted soybean. Surveys were done weekly using a standard fifteen inch diameter sweep net, from the R1 growth stage through the R7 growth stage. The object of this study was to determine the distribution of the cotton bollworm in soybeans and when soybeans play the largest role for these pest. Cotton bollworm were highest in normal planting dates with a mean number of 76.8 million cotton bollworm larvae being contributed from these planting dates.  Late planting dates had 4.25 million cotton bollworm larvae. When cotton bollworm larvae were corrected for percent positive samples for cotton bollworm, the means13.06 and 2.12 million cotton bollworm larvae for normal and late planting dates respectively. Bt soybeans will be a good fit in late planting dates since these late planting dates are not playing as large of a role in the natural refuge as normal planting dates.