Effects of pitch canker pathogen on gallery excavation and oviposition by Ips paraconfusus (Coleoptera: Scolytidae)
Abstract
Ips paraconfusus Lanier is a vector of the pitch canker fungus, Fusarium circinatum Nirenberg and O'Donnell, in California. Multiple infections of Monterey pine, Pinus radiata D. Don. (Pinaceae), branches and main stems appear to predispose trees to infestation by I. paraconfusus. The effect of cankers produced in response to F. circinatum on oviposition and gallery construction was investigated. Introduction of beetles into artificially induced or naturally occurring cankers was less likely to result in oviposition and resulted in shorter galleries than introductions into logs without cankers. Of all adults that produced eggs, the mean number of eggs per adult was no different in logs with cankers than in canker-free logs; however, the distance across the grain from the introduction point to the first egg was greater for adults introduced into cankers than for adults introduced away from cankers. These results indicate that the pitch canker pathogen has a negative effect on I. paraconfusus, as cankers produced in response to the pathogen are unsuitable for exploitation by the insect.