Project Summaries

09-517GA  Project Manager: P. F. O'Leary


Gregory T. Payne, Georgia Cotton Commission

Bollworm (CEW) and tobacco budworm (TBW) larvae and adults were collected from a variety of host crops and evaluated for susceptibility to MVP II®, cyperemthrin and spinosad (Tracer®) during the 2012 season. Results were compared to historical data collected throughout an eighteen-year study period beginning in 1995. As expected, CEW larvae were less susceptible to the effect(s) of MVP II® than TBW larvae. Throughout the study period, the susceptibilities of CEW and TBW larvae to MVPII® have been highly variable, but in general, LC50 values for MVPII® have decreased until the 2011and 2012 seasons. 2010 MVP II® LC50 values for CEW were among the highest recorded (ca. 10-fold higher than 2009 values); however, MVP II® mean LC50 values for 2011 and 2012 were 49-fold and 10-fold lower, respectively, than the 2010 MVP II® mean LC50 value. MVP II® LC50 values for 2012 TBW populations were the lowest values recorded. Although cypermethrin remains an effective insecticide to control CEW larvae, average LC50 values were highest during the 2011 season; the average LC50 value for cypermethrin against CEW larvae collected during the 2010and 2011 seasons were ca. 19-fold higher than the average LC50 values obtained during the mid-1990s. The effectiveness of cypermethrin for the control of TBW larvae has declined throughout the seventeen-year study period also; the average LC50 value for cypermethrin against TBW larvae collected during the 2011 season was ca. 61-fold higher than the LC50 value obtained for a pyrethroid-susceptible laboratory strain (HRV) and ca. 20-fold higher than the average LC50 values obtained during the mid-1990s. Although cypermethrin treated-diet and topical application bioassays were limited during the 2012 season, adult vial tests conducted on 2012 populations of CEW and TBW with cypermethrin have confirmed this trend. Spinosad (Tracer®) has remained highly effective against CEW and TBW larvae throughout the study period.


Project Year: 2012

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