Host suitability of nonmaize agroecosystem grasses for the western corn rootworm (Coleoptera: Chrysomelidae)

The biology of western corn rootworm larvae, Diabrotica virgifera virgifera LeConte, on alternate hosts has become an important topic with the recent commercialization of transgenic-rootworm maize. Larval development and survivorship were monitored on 22 plant species, including maize, Zea mays L.; maize-field weeds; and selected native prairie grasses, fence-row/forage grasses, and small grain crops planted in greenhouse trials. Small pots containing each plant species were infested with 25 western corn rootworm larvae from a nondiapausing strain. Larval recovery was monitored 7, 14, 21, and 26 d after infestation. The dry weight of larvae and adults was recorded in addition to pronotum width of adults and head capsule width of larvae. Larvae survived at least 14 d on 21 species and 26 d on IS species. Third instars were recovered from 16 species. The head capsule width of larvae recovered from quackgrass, Elytrigia repens L.; Rhodes grass, Chloris gayana Kunth; and fall panicum, Panicum dichotomiflorum Michx, were not significantly different from maize on all four sample days. Adults were recovered from 10 species. These data along with other studies show that almost all grasses tested provide enough nutrition for larvae of the western corn rootworm to survive 14 d, and larval development to the third instar can occur on most grasses. The potential for rootworm larvae to move between weeds within or adjacent to a maize field could be an important factor in resistance management of transgenic-rootworm maize. However, the long-term implication of such movement for a low-dose transgenic event has yet to be worked out.