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ARS Home » Research » Publications at this Location » Publication #46874
Title: BAIT ACCEPTANCE BY DIFFERENT GRASSHOPPER SPECIES AND INSTARS

Author
item Onsager, Jerome
item FOSTER R NELSON - USDA-APHIS-PPQ
item JECH LARRY - USDA-APHIS-PPQ

Submitted to: Technical Bulletin: Animal Plant Health Inspection Service
Publication Type: Experiment Station
Publication Acceptance Date: 6/19/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: The response of 31 species of rangeland grasshoppers to carbaryl bait was assessed. Nineteen of 25 serious pest species were considered susceptible (>30% control) as were four of five innocuous species. One species that has beneficial attributes (Hesperotettix viridis) was considered nonsusceptible. Small stages of some species were more susceptible than larger stages (i.e., the lethal dosage was lower), but some older populations suffered greater control than younger populations (i.e., their foraging range probably was greater). Consequently, the utility of selective bait treatments was confirmed. The interaction between vulnerability as affected by size and age was a new discovery. It suggests that timing of treatments against very young stages is not as important as it once had been considered.

Technical Abstract: Acceptance of carbaryl-treated wheat-bran bait by 31 different rangeland grasshopper species was quantified in 24 experiments at 14 sites. All but two of 16 "sensitive" species (i.e., that suffered >55% control) were serious pest species, as were five of seven "vulnerable" (30-54% control) species. Five serious pest species were "nonsusceptible" (<30% control), as was a non-pest species, Hesperotettix viridis, which is considered by some to be beneficial because it feed almost exclusively on weedy forbs. For three major pest species, young stages were more susceptible to bait than older stages of the same species. However, for two of those species, older populations suffered higher mortality than younger populations. These results suggest that some unknown compensatory mechanism is operating in a way that makes timing of application less important than had been thought heretofore.