Damage Appraisal and Management of the Western Pine Shoot Borer. Eucosma sonomana, in pine plantations in California. A Case Study : Insects Affecting Reforestation. Biology and Damage

1989

S. 110-123

6 Abb., 5 Tab., 11 Lit. Ang.

Unselbständiges Werk

200069380

The infestation frequency by western pine shoot borer, Eucosma sonomana Kearfott, following the establishment of pine plantations, and the degree of suppression and recovery of these infestations after mating disruption treatments of one growing season and five consecutive seasons, were studied in northeastern California. Treatment consisted of aerial spraying of pheromone (dodecenyl acetate). Height and radial-growth rates of pine trees with different periods of protection from infestation were compared with growth rates of unprotected trees in the same plantation. Shoot borer infestations began when the trees were about 5 years old and 1.3 m tall. Approximately 20% of the terminal shoots were infested when the trees reached age 10, and 60% when trees reached age 20. Trees comprising the tallest 50% of the stand were attacked more frequently than trees in the shorter half of the stand. Reductions in height growth of infested terminal shoots averaged 20% over all study trees and 27% in the taller half of the stand. Treated areas were associated with 66 to 84% fewer terminal shoot infestations. Trees protected for 5 years showed an average height-growth increase of 25.6% per year. Trees receiving one treatment showed an average height growth increase of 19.6% per year over the next 5 years. Timber-stand volumes were simulated for a rotation of 70 years by using the Prognosis growth and yield model. Growth simulations were tested for one application and five applications during stand-age intervals 16-20, 21-25, 26-30, and for an untreated control. On the basis of economic assumptions appropriate for market conditions of northeastern California, the treatments had benefit:cost ratios ranging from 7 to 0.5, with a single treatment applied to youngest stands yielding the most, and multiple treatments to the oldest stands the least benefits.