HOST-PLANT TRAITS ASSOCIATED WITH RESISTANCE OF PONDEROSA PINE TO THESAWFLY, NEODIPRION-FULVICEPS

Phenotypic variation in defoliation of ponderosa pine, Pinus ponderosa Laws., by the pine sawfly, Neodiprion fulviceps, is reported. Two fie ld and one laboratory bioassays of paired phenotypically resistant and susceptible trees consistently indicated that sawfly egg, larval, and total survival were 5-14% lower on resistant trees. A suite of host-p lant traits were assayed on resistant and susceptible trees including anatomical characteristics of the needles and concentration of terpene and nitrogen. Resistant trees had thicker outer cell layers, more fib er cells, higher toughness, and lower soluble nitrogen than susceptibl e trees. Resistant and susceptible trees were not distinguished by dif ferences in terpenes. Generational survival of N. fulviceps was invers ely related to foliage toughness and number of fiber cells.