A few borers, particularly clearwing borers and the Zimmerman pine moth, are considered more aggressive and are capable of damaging apparently healthy trees. Infestations of pinyon borers are thought to be related to excessive watering and rainfall that allows increased cracking in stems and trunks. Spray Timing Borers within trees cannot be successfully treated with insecticides because the Insects are in a protected site. Trunk sprays can kill the adult borers during egg laying and also may be effective against newly emerged larvae before they enter the trunk. Canopy spraying also may increase control of longhorned beetles and metallic wood borers.
Adults often feed on twigs and foliage before laying eggs.
Timing of trunk sprays varies with different borer species. The general time of adult emergence, associated with egg laying, is summarized in Table 1. For a few borers, the larvae remain exposed on the bark for a considerable period. This is particularly true for the Zimmerman pine moth, which hatches in late summer but does not tunnel into the tree until the following spring. For these Insects, treatments can be effectively applied from late summer through midspring.