Submitted to: American Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 2003
Publication Date: March 20, 2004
Citation: Horton, D.R., Lewis, T.M., Broers, D.A. 2004. Ecological and geographic range expansion of the introduced predator Anthocoris nemoralis (Heteroptera:Anthocoridae). American Entomologist. 50:18-30. Interpretive Summary: Pear psylla is a major insect pest of pear in North America, requiring expensive control measures, often including pesticide applications. Scientists at the USDA-ARS Yakima Agricultural Research Laboratory are investigating the potential of predatory insects for biological control of pear psylla as an alternative to pesticide sprays. It was found that a predatory bug called Anthocoris nemoralis has expanded its geographic and host plant range greatly since its introduction and probably feeds in several species of psyllids. This information is useful in assessing the potential of A. nemoralis as a predator of pear psylla across geographic and ecological areas and its potential to move from wild plants to commercial pear.
Technical Abstract: Anthocoris nemoralis is a predatory bug native to the Palearctic region. The predator established in North America due to at least one unintentional introduction made sometime before 1960, and an intentional introduction made in the early 1960s to control a psyllid pest in pear orchards. Recent collecting efforts suggest that A. nemoralis has expanded both its geographic range and host plant range. It is now found in western North America from southern California northward into British Columbia. An eastern population located on the Niagra peninsula was reported in the 1950s-1970s, and apparently remains established in that area. Both Old and New World populations of A. nemoralis prefer plant species that host psyllid prey. In North America, A. nemoralis has been recorded from 13 plant genera, of which 11 host psyllids. This percentage is much higher than the percent of North American tree and shrub genera that host psyllids, suggesting that A. nemoralis in North America has preferentially colonized plants that host psyllids, including plants that do not occur naturally in the native Old World range of A. nemoralis. Several of the plant genera are hosts to newly arrived psyllids from South America and Australia. Concerns have been expressed that the introduced predator in North America may adversely affect native anthocorids, particularly species that occur in pear orchards: Anthocoris antevolens, A. tomentosus, and A. musculus. Overlap in plant genera used by four native anthocorids and the introduced A. nemoralis was highest between A. nemoralis, A. antevolens, and A. tomentosus. Surveys of native tree and shrub species in North America that host psyllids should be done to determine actual range expansion by A. nemoralis, and to provide information about potential competition between native anthocorids and A. nemoralis.