Weed seed granivory by carabid beetles and crickets for biological control of weeds in commercial lowbush blueberry fields

Weeds are one of the most limiting factors in the commercial production of lowbush blueberries V accinium angustifolium ( E ricaceae). Sheep sorrel ( R umex acetosella ) and hairy fescue ( F estuca tenuifolia ) are prominent weeds in lowbush blueberry fields. Because the granivorous insects H arpalus rufipes ( C arabidae) and G ryllus pennsylvanicus ( G ryllidae) are common in lowbush blueberry fields when sheep sorrel and hairy fescue are dispersing seeds, we examined how granivorous insects can contribute to the biocontrol of these weeds. In the laboratory, H . rufipes and G . pennsylvanicus consumed a significant number of seeds of sheep sorrel and hairy fescue, and a field experiment found that insects probably consume a significant number of sheep sorrel and hairy fescue seeds in blueberry fields. Additional experiments found that H . rufipes was highly susceptible to field rates of phosmet and acetamiprid, although not to field rates of spirotetramat, which are insecticides that may be used in blueberry fields when the beetle is active. Natural populations of granivorous insects probably provide a valuable ecological service in commercial lowbush blueberry fields and should be conserved in the development of integrated weed management programmes.