Submitted to: Journal of Stored Products Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/14/2004
Publication Date: 6/10/2005
Citation: Arbogast, R.T., Chini, S.R. 2005. Abundance of Plodia interpunctella (Hubner) and Cadra cautella (Walker) infesting maize stored on South Carolina farms: seasonal and non-seasonal variation. Journal of Stored Products Research. 41:528-543. Interpretive Summary: Protection of grain and cereal products against damage and contamination by insects during storage, processing, and marketing has relied heavily on routine application of chemical insecticides. However, increasing concern about the health and environmental hazards of insecticide application, has made it necessary to seek new pest control methods that minimize chemical risk. These new methods will rely as much as possible on natural control agents such as weather and natural enemies, but will also employ a variety of biological, physical, and chemical control measures. Development of such methods will require an intimate knowledge of natural factors and their influence on the distribution and abundance of insect pests. Scientists at the Center for Agricultural, Medical and Veterinary Entomology, ARS, USDA, Gainesville, Florida, have established information relating insect pest abundance in farm storage bins to various biological and physical factors. This information will be useful to researchers developing new control methods that exploit natural factors and minimize pesticide application, and will also assist farmers and grain elevator operators in predicting insect problems and timing application of control measures.
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.