Conifer Shoot Borers. A Review of Some Major Forest Pests

1990

zahlr. Lit. Ang.

Unselbständiges Werk

9087

200085810

Shoot boring insects in the genera Eucosma, Pissodes and Rhyacionia are important pests of conifers, particularly pines, in many parts of the world. Attacks by these pests are generally most serious during stand establishment and prior to crown closure. Damage consists of growth and/or form loss, decreased wood quality, increased rotation periods and, occasionally, death of heavily infested trees. Damage is usually most common in open stands withsparse nonhost vegetation. Cultural practices such as intensive site preparation or release treatments that remove or decrease competing vegetation often increase pest populations and damage. Establishment of extensive areas of single-species plantations often exacerbates problems with shoot borers. Hosts growing on low quality sites, or sites to which they are poorly adapted, are often more susceptible to some lepidopterous shoot borers, particularly Rhyacionia spp. In contrast, Pissodes spp. tend to select the largest and apparently healthiest trees within a given stand. Silvicultural practices for minimizing shoot borer damage include establishment of hosts on sites for which they are adapted, since vigorous trees are more tolerant of injury than stressed trees. Maintaining fully stocked stands also reduces the potential for shoot borer damage. Although they are effective in some situations, pesticides are regarded as emergency control measures and are therefore not incorporated into management plans. Future control techniques may include enhancement of biological control agents such as parasites, predators, viruses and bacteria and development of resistant trees via genetic engineering or tree breeding.