HOST-PLANT AFFECTS THE INTERACTION BETWEEN THE RUSSIAN WHEAT APHID AND A GENERALIST PREDATOR, CHRYSOPERLA-CARNEA

Greenhouse and field experiments were conducted to determine whether h ost-plant species affects the ability of a generalist predator to redu ce populations of the Russian wheat aphid, Diuraphis noxia (Mordvilko) . Aphid colonies were allowed to develop on six species of cool-season grasses for 10 days, after which half of the plants received five neo nate larvae of the common green lacewing, Chrysoperla carnea (Stephens ). Lacewing larvae substantially reduced aphid density on both grass s eedlings (in the greenhouse) and mature plants (in the field). The lev el of control varied among grass species, however. Aphid populations w ere reduced to zero or near zero on two slender-leaved grasses (Indian ricegrass and bluebunch wheatgrass), but were maintained at moderate densities on a pubescent cultivar of intermediate wheatgrass. Mechanis ms underlying this tri-trophic interaction are unknown, but plant morp hology may play an important role because of the ''leaf-galling'' habi t of D. noxia.