EFFECT OF MANURE ON MAIZE - TOLERANCE TO WESTERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

This study evaluated the potential of manure and maize tolerance to se rve as alternative management strategies for reducing yield losses in maize, Zea mays (L.), by the western corn rootworm, Diabrotica virgife ra virgifera (LeConte). The interactions between manure and 2 maize hy brids and their subsequent effects on the growth and development of ma ize infested with western corn rootworm were investigated in 1992 and 1993. Treatment combinations included 2 maize hybrids (Pioneer hybrid 3733 and Cornell 281). 4 manure rates (0, 45, 90, and 135 MT/ha), and 3 western corn rootworm egg densities (1992: 0, 500, 700 eggs per 30.5 -cm row; 1993: 0, 400, 800 eggs per 30.5-cm row). All plots received a dequate nutrients (supplied by manure, inorganic fertilizer, or both) to satisfy or exceed soil test recommendations. Manure increased plant height, root recovery, and overall silage and grain yields, and decre ased early feeding injury and lodging in 1 or both years of the study. However, manure had no effect on final root injury or on silage quali ty. Effects of manure were seemingly more pronounced in a wetter than average year. Pioneer 3733 had lower root injury ratings at the low we stern corn rootworm density in 1993, equal root recovery, less lodging , and higher silage and grain yields with less loss to western corn ro otworm than Cornell 281. In both hybrids, manure produced an environme ntally induced tolerance by increasing root recovery and in some cases reducing yield losses.