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U.S. Cottonbelt Survey: Testing the Susceptibility of the Bollworm, Helicoverpa zea (Boddie), to Pyrethroid Insecticides—2001 Update

G.T. Payne, J. Adamczyk, J.S. Bacheler, R.D. Bagwell, M.L. Boyd, Clifton Brister, B.L. Freeman, A. Herbert, G.A. Herzog, D.R. Johnson, M.B. Layton, G. Lentz, B.R. Leonard, N. Liu, S.H. Martin, P.V. Pietrantonio, M.E. Roof, R.K. Sprenkel, M.J. Sullivan, J.W. Van Duyn and J.R. Weeks


ABSTRACT

In 2001, more than 15,000 bollworm moths and 4000 budworm moths were bioassayed. Survival values for bollworm moths at the 5 µg/vial concentration and 10 µg/vial concentration of cypermethrin were similar to survival values recorded during the 2000 season. Six sites had greater than 10% survival during at least one month at the 10 µg/vial concentration and 11 sites had greater than 5 % survival. This represented a 1.2-fold increase compared to data collected during the 2000 season, a 2-fold increase compared to data collected during the 1999 season and a 6-fold increase compared to data collected during the 1998 season. Survival at the 10 µg/vial concentration of cypermethrin ranged from a low of 0% to a high of 50%. As expected, survival values for tobacco budworm adults at the 10 µg/vial concentration of cypermethrin were high throughout the mid-south/southeastern test areas. All eighteen test sites had greater than 10% survival; eight of eighteen sites had greater than 50% survival; and two of eighteen test sites had greater than 70% survival. Survival at the 10 µg/vial concentration of cypermethrin ranged from a low of 12% to a high of 76%. Survival of bollworm adults at a 15 µg/vial concentration of spinosad ranged from a low of 0% to a high of 57%. Eight of 33 sites evaluated had greater than 20% survival; three of 33 sites evaluated had greater than 50% survival. Tobacco budworm adults were less tolerant of spinosad treatment. Survival of tobacco budworm adults at a 15 µg/vial concentration of spinosad ranged from a low of 0% to a high of 24.4%. Only five of 19 sites evaluated had greater than 10% survival, and only one of 19 sites evaluated had greater than 20% survival. These data suggest that bollworm populations throughout the mid-south/southeastern U.S. are developing resistance to the pyrethroid insecticides; resistance to pyrethroids in tobacco budworm populations is widespread; and efforts to monitor pyrethroid resistance and the effects of spinosad in bollworm populations should remain a priority for the development and implementation of future resistance management strategies.





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Document last modified May 20, 2002