Forest and Shade-Tree Insect Pests

Many coleopteran pests of forest and shade trees produce an aggregation pheromone that attracts both sexes of adults, which represent 

The aggregation pheromone of the western pine beetle, Dendroctonus brevicomis, which kills stressed or even apparently healthy ponderosa pines, consists of three components, one produced by the male, one by the female, and one by the host tree (266 and refs, therein). Wood (528) and Wood and Bedard (534) have summarized the results of large-scale attempts at population suppression based on mass trapping. Wood et al. (515) discuss integrated pest management of the western pine beetle Bedard et al. (535) discuss the role of behavior modifying chemicals in the management of the western pine beetle. 

Since the survival of the beetle depends on overwhelming individual trees in the aggregation phase mediated by the pheromone, control strategy depends on reducing the intensity of these attacks. Two approaches have been used. 1. Large sticky traps baited with the pheromone have been distributed throughout the area of infestation to reduce the number of beetles available to attack trees (trap-out method). 2. The forest canopy has been permeated either with the pheromone or with an anti-attractant. 

Permeation with the 3-component pheromone over a 0.81 hectare plot prevented the beetles from being trapped on traps baited with the same pheromone in the center of the treated area 536), When verbenone was released from formulations attached to ponderosa pine trees that were also baited with the pheromone, no mass attack occurred on these trees, in contrast to the mass attacks that occurred on trees that were simply baited with the pheromone. Further development of this approach is warranted to develop a method for protecting individual high-value trees. 

One further feature that requires additional study is the effect of the pheromones on natural enemies. Virt 537) cites this effect as a disadvantage of trap-out he prefers the use of baited trees when timely removal is feasible. 

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