STATUS OF BIOLOGICAL-CONTROL IN VEGETATION MANAGEMENT IN FORESTRY

Biological control traditionally depends upon importing the natural en emies of introduced weeds. Since vegetation management in forestry has primarily been aimed at protecting economic species of trees from com petition from other native plants, biological control has been of litt le use in forestry. An alternative approach to controlling unwanted na tive plants, supplementing their existing complex of natural enemies w ith introduced insects found attacking closely related plants, is bein g used on rangeland, but is not recommended for forestry. New agents w ill not remain restricted to the location where they are released, but will spread and would eventually affect the target plant throughout i ts entire range, including areas where it might be desirable. A more p romising alternative is manipulating one or more insects or diseases t hat already attack the undesirable plants. Many plant pathogens natura lly associated with a particular plant species are highly virulent and specific to only the target plant. Mass producing these pathogens and applying them with conventional spray systems is being used in agricu lture and is being considered for forestry. Other methods of manipulat ion, such as mass rearing insects and releasing them to attack the und esirable plant or manipulating populations of the insect predators tha t naturally suppress phytophagous insects of a target plant, are discu ssed.