The effects of rainstorms on soybean aphids, Aphis glycines (Matsumura)

Abstract

Soybean aphid, Aphis glycines (Matsumura), is a significant economic pest of soybean in North America. Three experiments were conducted to determine the influence of abiotic factors on aphid populations and distribution on soybean plant canopies. Aphids were exposed to rainfall simulations in field and in greenhouse settings while resident populations were observed before and after rainstorm events. Aphis glycines population changes were influenced most greatly by sample period and a sample period*treatment interaction during in-field rainfall simulation. Shifts in population distribution were significantly influenced by sample period and interactions between sample period and location of the plot, canopy level and treatment. Visual comparisons before and after trials indicated that small dips in population and random shifts in canopy population distribution quickly returned to original levels after the application of rainfall. An in-field aphid observational study indicated that some abiotic factors associated with rainstorm events are conditionally significant. Average wind speed, the interaction between maximum observed wind speed and rainfall, average aphid starting population and location/soil type of the observed field significantly affected aphid population. Sample period and pre-count averages were found to be significant to aphid distribution on the plant canopy.