Illinois Natural History Survey - University of Illinois

The Beetle That Tried to Steal Christmas

The pine shoot beetle, Tomicus piniperda, is one of the more recent of the 360 or more exotic insects of woody plants now established in North America. A native of Europe, Asia, and North Africa, T. piniperda has a long history of interceptions at U.S. ports of entry on wood products such as crates, pallets, and dunnage. Established populations were first discovered in Ohio in 1992, but the fact that infestations were discovered in six surrounding states, including Illinois, within a month of the initial discovery suggests that this bark beetle had been in the U.S. for several years prior. Given its wide distribution within the Great Lakes region, eradication was not a consideration, but federal and state quarantines were imposed to restrict the movement of the pest and infested materials. Regulations associated with these quarantines have been especially difficult for Christmas tree growers who ship large numbers of pines to southern or western states.

The pine shoot beetle, Tomicus piniperda.

Pine shoot beetle (PSB) has found the temperate climate and widespread occurrence of pine forests, Christmas tree plantations, and nurseries within the Great Lakes region highly suitable for colonization. Research has shown that PSB can use most, if not all, North American pines as hosts for breeding and shoot feeding, and since it is the first pine bark beetle to fly in spring, it has a competitive advantage over other native species of pine bark beetles. Adult PSB overwinter in the bark at the base of pine trees, but emerge in early spring and fly to recently killed or cut pine trees, logs, stumps, and pine slash. Eggs are laid beneath the bark of such brood material where larvae feed and develop. Progeny adults emerge in early summer and feed in tunnels in the shoots of live pines before moving to overwintering sites following the first hard frost. While high adult numbers can kill shoots and reduce tree growth, PSB populations have as yet had little impact on well-managed Christmas tree plantations.

In fact, in spite of its widespread distribution, PSB has not caused significant levels of damage to native forests anywhere within its new North American range. Nevertheless, existing quarantines have had major economic impacts on forest, nursery, and Christmas tree industries. Based on continuing research and the realization that PSB is here to stay, an integrated management program was developed to reduce beetle numbers in Christmas tree farms and reduce the overall burden of restrictive quarantine regulations. At certain stages of its life cycle, PSB is deemed particularly vulnerable to management actions. For instance, timely placement and destruction of trap logs can be effective in reducing adult beetle populations, good sanitation practices can eliminate brood material, and a single cover spray can control beetles during shoot feeding.

This integrated management concept has been formalized into a Pine Shoot Beetle Compliance Program. Growers who enroll in the program agree to a set of management guidelines and schedules along with scouting and strict record-keeping of their compliance with these management procedures. In return, if management practices and deadlines are fully met, growers in regulated areas can ship trees in the fall without restriction. Although this implies a certain element of risk of PSB presence on trees coming from compliance locations, preliminary data suggest the risk is minimal, if not less, than for trees grown under the more traditional regulations. This novel regulatory approach for an exotic pest appears both practical for growers and effective against the pest.

Charles Helm, Center for Economic Entomology; James Appleby, University of Illinois

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