Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: July 1, 2006
Publication Date: N/A
Technical Abstract: Seasonal trends and short-term fluctuations in abundance of Plodia interpunctella (Hübner) and Cadra cautella (Walker) infesting corn stored on two South Carolina farms were studied during three storage seasons. Coils of corrugated paper placed on the grain surface were used to trap mature larvae seeking pupation sites. Temperatures in the grain (8 cm deep) and in the bin headspace were recorded hourly, and grain moisture content was measured weekly. Weekly mean numbers of moth larvae, and adults of two natural enemies, trapped in the coils were used for tracking changes in their abundance over time. The most significant findings were: (1) a seasonal pattern of abundance in both moth species that persisted from farm to farm and year to year, and (2) the coincidence of the highest population levels with the lowest temperatures. With few exceptions, the moth populations increased in the fall, reached their highest levels in winter, and then declined to low levels by early spring. The persistence of this pattern suggests a seasonal regulatory mechanism, with the onset of adversely high temperatures as a major cause of population collapse. This view is supported by published information on the upper temperature limits for development and on the adverse impact of high temperature on reproduction, in conjunction with the temperature records for spring and early summer, especially in the headspace of the bin. Superimposed upon the seasonal trends were short-term, non-seasonal cycles of abundance with variable periods. Population theory suggests that predation, parasitism, disease, and competition may have produced these cycles.