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Title:Susceptibility of Oriental fruit moth, (Grapholita molesta (Busck)) to selected insecticides and mixtures
Author(s):Jones, Moneen M.
Director of Research:Weinzierl, Richard A.
Doctoral Committee Chair(s):Weinzierl, Richard A.
Doctoral Committee Member(s):Bollero, German A.; Hanks, Lawrence M.; Kushad, Mosbah M.; Spencer, Joseph L.; Robertson, Jacqueline
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Insecticide resistance
Resistance monitoring
Abstract:A series of experiments assessed the susceptibility of Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), to selected insecticides and mixtures. Two populations – a laboratory colony from Rutgers University and a colony established in 2007 from orchards in Calhoun County, Illinois – were tested. Both colonies were reared concurrently on lima bean diet and ‘Gala’ apples to reduce the likelihood that either colony would be lost to diseases or other factors. Bioassays were analyzed separately for each colony and for progeny of parents reared on each food source. To determine the baseline susceptibility of G. molesta to chlorantraniliprole, spinetoram, spinosad, acetamiprid, thiamethoxam, esfenvalerate, and lambda-cyhalothrin, neonates were placed on wheat germ diet containing a range of concentrations of each insecticide. Overall, the two colonies responded similarly to these insecticides, regardless of parental food source. Results of these bioassays provide baseline data for future monitoring of of resistance. To develop and test a diagnostic dose for estimation of pyrethroid resistance in the field, the dose-mortality relationship was described for esfenvalerate applied topically to adult males. A range of concentrations was applied in 1 μl of acetone to male moths from the Rutgers colony, and the LD99 was estimated to be 0.022 μg per moth. Application of 0.022 μg esfenvalerate per moth to ca. 600 male moths from two putatively susceptible populations resulted in mean survivorship approximately equal to the expected level of 1.0%. Application of this dose to ca. 375 moths captured in two Calhoun County orchards with histories of pyrethroid use resulted in mean survivorship of 9.4% and 82%. It is proposed that 0.022 μg of esfenvalerate in 1 μl of acetone be used as a diagnostic dose for monitoring pyrethroid resistance. iii The toxicities of three mixtures of insecticides to neonates were estimated. Chlorantraniliprole was mixed with acetamiprid, esfenvalerate, or thiamethoxam. These insecticides may be mixed or rotated to provide broad spectrum control of orchard pests. Mixtures of chlorantraniliprole with acetamiprid or thiamethoxam did not exhibit consistent synergism or antagonism. For chlorantraniliprole plus esfenvalerate, mortality was less than expected at nearly all concentrations for both colonies, suggesting antagonism despite different modes of action for the two compounds. The effectiveness of one or both insecticides to Oriental fruit moth might be reduced if they are combined in field applications. To estimate the toxicity of novaluron, an insect growth regulator, to eggs of the two colonies, eggs on waxed paper were dipped into a range of concentrations. Eggs from the Calhoun colony were more tolerant to novaluron than eggs from the Rutgers colony. Differences in the responses of these colonies may represent natural variation among populations or may be the result of selection by other insecticides used in orchards in Calhoun County before larvae were collected to establish this colony.
Issue Date:2010-08-20
Rights Information:Copyright 2010 Moneen M. Jones
Date Available in IDEALS:2010-08-20
Date Deposited:2010-08

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