Interactions among grasshoppers (Orthoptera: Acrididae) in intermountain grassland of western North America [Oedaleonotus enigma, Melanoplus packardii]

alfalfa biological competition carbaril carbaryl chemical control control de plagas especies grasslands herbage lucerne lutte antiravageur lutte chimique luzerne medicago sativa melanoplus sanguinipes pest control pests of plants plagas de plantas population density population dynamics praderas ravageur des plantes species utah