Ecology of interactions between weeds and arthropods.

Weeds and arthropods interact in agricultural systems. Weeds can directly serve as food sources or provide other ecosystem resources for herbivorous arthropods, and indirectly serve carnivorous (beneficial) arthropods by providing food and shelter to their prey. Weeds can serve as alternative hosts for pest and beneficial arthropods when their preferred crop host is absent. Herbivory on crops by pest arthropods reduces the competitive ability of crop plants, leading to increased weed growth. Interactions between weeds and arthropods have several implications to integrated pest management (IPM). Pest and beneficial arthropod populations can be maintained in the absence of crop hosts. This statement also applies to all other pests that use weeds as a food source, including pathogens, nematodes, mollusks, and vertebrates. Weeds outside crop fields that maintain overwintering populations of arthropod pests are the major reason for the development of area-wide IPM programs for certain mobile arthropod pests. Weeds can serve as a source of increased diversity in agroecosystems. Increased diversity has been the rationale for enhancing biological control of arthropod pests through habitat management. The consequences of such approaches are difficult to predict on a multispecies IPM basis.