Modeling corn rootworm (Diabrotica spp.) emergence in light of Bt-RW traits and resistance

Corn rootworm (Diabrotica spp.) is a major agricultural pest of corn (Zea mays L.) in the Corn Belt.  Resistance to corn producing Bacillus thuringiensis Berliner (Bt) proteins necessitates adaptive management that considers field-specific management. Scouting adult populations during emergence could warn growers of developing resistance and facilitate better management decisions the following year.  The key is knowing when to assess the egg-laying population in the field; degree-day models could time (define) scouting windows reflecting traditional elements (species, planting date, soil /air temperatures) as well as Bt-RW trait(s) and Bt-RW resistance. This poster reports preliminary research on the accuracy and utility of an existing corn rootworm model in predicting beetle emergence from Bt-RW and non-Bt-RW corn hybrids at selected MN sites. Emergence from a Bt-susceptible (Rosemount, MN) and a Bt-resistance (Hills, MN) population of western corn rootworm (Diabrotica virgifera virgifera Leconte) was monitored 2-3X per week using cut-plant emergence cages. Preliminary analyses examined locale, trait and resistance dimensions with the goal of determining how well existing models work in predicting adult emergence.  Results will be used to modify the emergence models, which will be further evaluated against 6 other MN site-years. We anticipate conducting a parallel research course with northern corn rootworm (Diabrotica barberi Smith and Lawrence) emergence.