Pine Engraver Biological Control
Ips pini (Say)
From: Bellows, Thomas S. ,Carol Meisenbacher, and Richard C. Reardon, 1998, Biological Control of Arthropod Forest Pests of the Western United States: A Review and Recommendations, USDA, FS, FHTET-96-21.
Origin: North America.
Range in North America: Throughout North America.
Plant hosts and damage: Pinus spp., commonly in P. jeffreyi, P. ponderosa, P. contorta. The adults bore into the bark, and construct an oviposition chamber between the bark and the wood, on limbs or the bole of the tree. The larvae feed between the bark and the wood, killing limbs or tree tops. Severe infestations can kill trees.
Natural Enemies: Natural enemy associations are very poorly understood for Ips pini (and other Ips spp.). Predators, pathogens, and parasitoids have been reported either associated with or parasitizing I. pini (Table 8).
Table 8. Natural enemies associated with or reported from Ips pini
Pest Status: Ips pini is one of the most common bark beetles in North America, and at times becomes a serious pest. Large populations can develop in the tops or limbs of trees killed by Dendroctonus spp. or in slash from logging. When populations become large, they become aggressive and attack healthy trees. Outbreaks are usually of short duration and seldom last more than one season (Furniss and Carolin 1977). There may be from one to five generations per year, depending on locality and length of season.
Biological Control: Very little is known about the role of natural enemies in the population dynamics of Ips spp., including I. pini. Raffa (1991) and coworkers have identified predaceous beetles that are attracted to I. pini pheromone (ipsdienol). These beetles are known to prey upon other bark beetles and are likely predators of I. pini. A number of nematodes, some with parasitic life cycles, are known from I. pini. Choo et al. (1987) reported up to 99% infection in some populations of I. pini, but the impact of such parasitism on beetle population biology is unknown. Senger and Roitberg (1992) demonstrated reduced fecundity in adult I. pini parasitized by the pteromalid wasp Tomicobia tibialis. Parasitized adults produced only half the number of progeny of nonparasitized adults. The absolute or relative abundance of natural enemies in Ips populations is not well documented.
Recommendations: Outbreaks of this species are self-limiting and usually of short duration. The species has an extant upper trophic level of predators and parasitic natural enemies, and usually reaches serious levels only in the presence of large amounts of breeding material. Therefore, management options should focus on limiting the availability of this breeding material. Control practices with pheromones have been proposed and evaluated (Raffa 1991 and references therein), but the pheromones also act as kairomones to many predators. If pheromones are used in trapping, technologies should be developed so as not to unduly trap natural enemies and harm the balance of natural enemies to pests. Some natural enemies may be reared or collectable in large numbers, but the scale of application necessary to employ them in augmentation programs is likely prohibitive. Additional biological control actions do not appear warranted at this time. Should additional interest in biological control arise, the first needs to be addressed would be quantitative research into the roles of natural enemies in endemic and epidemic beetle populations.
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