Comparison of three trap types for monitoring insect populations in storedgrains

Three trap types-probe, cone, and sticky-were used to monitor insect popula tions infesting shelled maize, Zea mays L., housed in galvanized steel stor age bins. Sticky traps were suspended in the headspace 1 m above the grain mass, probe traps were inserted into the grain near the top and bottom of t he grain mass, and cone traps were positioned at the surface of the grain m ass. Although there was some overlap, each trap type was rather specific in the range of insect species trapped. Probe traps positioned near the grain surface trapped mostly Oryzaephilus surinamensis (L.), Tribolium castaneum (Herbst), and Cynaeus angustus (LeConte) whereas those positioned near the bottom of the grain mass trapped mostly Sitophilus zeamais Motschulsky. Co ne traps caught mostly Typhaea stercorea (L.), Cryptolestes spp., and Ahasv erus advena Waltl. Sticky traps caught primarily stored-product moths [Plod ia interpunctella (Hubner) and Sitotroga cerealella (Olivier)] and A. adven a. In addition to catching pest species, done traps also caught hemipteran predators and hymenopteran parasitoids, and sticky traps caught large numbe rs of parasitoids. Although probe traps caught smaller numbers of several p est species than cone traps, these traps generally detected the presence of these species at the same time as cone traps, in addition to trapping othe r species that were not detected at all in cone traps. Therefore, a combina tion of sticky traps in the grain bin headspace and probe traps positioned just below the grain surface is probably most efficient for monitoring the presence of pest and beneficial insect species in grain storage. If pests c annot be eliminated from the space beneath the false floor of a grain bin, probe traps set at the bottom of the grain mass should provide the best ear ly warning of infestation by species colonizing a grain mass by this route.