RESISTANCE AGAINST WHITE-PINE WEEVIL - EFFECTS ON WEEVIL, REPRODUCTION AND HOST FINDING

Feeding on leaders of resistant Sitka spruce trees, Picea sitchensis ( Bong.) Carr., led to ovarian regression in white pine weevils, Pissode s strobi Peck., that contained already mature eggs at the time of cagi ng on leaders. Such feeding also led to inhibition or a virtual blocka ge of ovarian development in weevils that did not contain already matu re eggs at the-time of caging. Ovarian maturation in such weevils was restored by application of juvenile hormone to female weevils. Effects of three levels of resistance were consistent within the experiments and with the field performance of the tested clones. These results ind icate that the effects of resistance were postingestive, i.e., resista nce was a form of antibiosis. How antibiosis can cause the weevils to concentrate oviposition on susceptible trees is discussed. Results als o provide a means of selecting and ranking resistance of individual sp ruce trees for tree breeding and reforestation.