Host stress influences oviposition preference and performance of a pine sawfly

Abstract.

• 1 The effect of ponderosa pine (Pinus ponderosa Doug]. ex Laws) water stress, measured by xylem water potential, on oviposition preference and egg development of Neodiprion fulviceps was determined by two laboratory experiments in 1987 and 1988.
• 2 In the first experiment, adult females were allowed to choose between foliage from water-stressed, watered, and untreated control trees.
• 3 Significant differences were found between treatments in xylem water potential in 1987 but not in 1988.
• 4 Females chose water-stressed trees and a positive correlation was found between female preference and xylem water potential in 1987 but not in 1988.
• 5 In the second experiment, females were placed in globe cages with a single branch from each treatment and allowed to oviposit.
• 6 Significant differences were found among treatments in egg survival in 1987 but not in 1988.
• 7 These results indicate that sawflies can distinguish between stressed and non-stressed trees and that this behaviour is adaptive in that egg survival was greatest on the preferred treatment.