The refuge strategy proposed to mitigate corn borer resistance to Bt-corn requires dispersal information to address its assumption of random mating. Mark and recapture of lab-reared insects may be affected by changes in insect development or in flight propensity. We propose to use the trace elements Rubidium (Rb) and Cesium (Cs) to mark field reared southwestern corn borer (SWCB) for mark and recapture work. In preliminary greenhouse tests, potted non Bt-corn plants at the 6-8 leaf stage were sprayed with three levels of RbCl and CsCl: 100, 1000 or 10,000 ppm. The plants were inoculated with SWCB neonates. Plants were dissected 5 weeks later to record SWCB survival. Insects and plant parts were collected for analysis of Rb and Cs. There was no significant effect (P=0.05) of different levels of each element on the survival, pupal period, adult eclosion, male and female dry weight or moth deformity. The flame Atomic Absorption Spectrophotometer AAS (Perkin Elmer AAnalyst 100) was effective in measuring Rb and Cs differences among three application rates in various plant tissues. However, the flame AAS was not sensitive enough to measure differences in Rb and Cs in SWCB moths from treated or untreated plants. The graphite furnace AAS was sensitive enough to reliably measure differences in Rb and Cs concentrations in SWCB moths from treated or untreated plants. A 10-fold difference was recorded in males and 64-fold difference was recorded in females between native SWCB and SWCB from plants treated at 1000 ppm CsCl. There were also significant differences between marked and unmarked moths in a lab experiment. A preliminary Neutron Activation Analysis (NAA) was also able to detect differences in Rb and Cs in SWCB moths that were marked or unmarked with RbCl or CsCl.
Species 1: Lepidoptera Pyralidae Diatraea grandiosella (southwestern corn borer)
Keywords: Bt-corn, resistance management
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