Variability in weed biological control: effects of foliar nitrogen on larval development and dispersal of the alligatorweed flea beetle, Agasicles hygrophila

Publication date: Available online 3 May 2019Source: Biological ControlAuthor(s): Nathan Harms, James T. CroninAbstractHost quality can have dramatic effects on performance of biological control agents but its importance is understudied. We used a combination of field measurements and laboratory experiments to determine the range of foliar nitrogen (FN) that larvae of the alligatorweed flea beetle are exposed to in the field and its importance to larval development and dispersal. Seasonal variability in FN was assessed at field sites spanning southern to northern Louisiana every 2-3 weeks during the growing season for four years. In a series of laboratory experiments, alligatorweed FN was manipulated to examine its influence on larval development and survival (under different temperature regimes), adult biomass, and dispersal of the biological control agent, Agasicles hygrophila. There was strong seasonality of FN in field sites with peak levels (4-8 % dry weight nitrogen; DW N) recorded early during each year, declining during summer, and slightly increasing again in the fall which coincides with flea beetle activity. Foliar nitrogen and rearing temperature had strong independent effects on larval development rate. High FN increased survival by 40%, decreased developmental time by 15%, and resulted in 11% larger adults. Increasing temperature reduced survival by 43%, shortened developmental time by 28%, and led to 15% smaller adults. In the dispersal experiment we were unabl...
Source: Biological Control - Category: Biology Source Type: research