Using five sampling methods to measure insect distribution and abundance in bins storing wheat

Newly-harvested wheat stored in each of two bins on each of two farms in Ka nsas during each of 3 years was sampled every 3-4 days at two locations (in the center and midway between the center and bin wall) within each bin. Th e variation in insect numbers between bins, locations within a bin, farms a nd years differed with insect species and sampling method. Five sampling me thods were used to monitor insect populations in three regions of each bin: (1) in the head space above the grain; (2) on the grain surface; and (3) w ithin the top 50 cm of the grain mass. Cryptolestes ferrugineus (Stephens) and Ahasverus advena (Waltl) were more evenly distributed among these three regions of a bin than the other species. Typhaea stercorea (L.) were found mainly in the head space and on the grain surface. These distribution patt erns were consistent throughout the 126-day storage period. R. dominica (F. ) were found in the head space and within the grain mass early in the stora ge period, and mainly in the grain mass as grain cooled in the autumn. The majority of Plodia interpunctella (Hubner) (91%) were caught in sticky trap s in the head space. Two of the three less abundant species, Sitophilus ory zae (L.) and Tribolium castaneum (Herbst), tended to be found most often on the grain surface and the other, Oryzaephilus surinamensis (L.), within th e grain mass. The sampling method often influenced the results. Emergence t raps captured greater numbers of A. advena than other species. More R. domi nica were found in grain samples than in traps in the autumn. Pushing probe traps below the surface of the grain reduced the numbers of T. stercorea, A. advena, S, oryzae and T. castaneum captured. Differences between species and times during the storage period in the effectiveness of different samp ling methods need to be considered in making pest management decisions. Pub lished by Elsevier Science Ltd.