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Mechanisms Underlying Resistance of Strawberry Cultivars to Tarnished Plant Bugs 2001

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Project Leader(s): Greg English-Loeb and Marc Rhainds, Department of Entomology, NYSAES, Cornell University, Geneva, NY 14456

Type of grant: Pest-resistant crops

Applicability: Throughout the Northeast United States

Abstract: The present study investigated mechanisms that underlie resistance of strawberry cultivars to tarnished plant bugs, Lygus lineolaris (Hemiptera: Miridae). Inter-plant distribution of emerged nymphs in cage experiments suggests that females lay more eggs on plants with numerous fruits, although cultivar per se did not influence oviposition behaviour of females. A large number of nymphs emerged from the inflorescence of strawberry plants, which suggests that ovipositing females may cause extensive damage to strawberry fruits. Distinct within-plant distribution of emerged nymphs for different cultivars further suggest that the relative damage caused by ovipositing females may vary for different cultivars. Foraging nymphs did not exhibit a preference for any strawberry cultivar, although the incidence of nymphs increased with fruit weight, especially for late instars; these results suggest that the phenology of host plants rather than cultivar per se may influence the distribution of plant bugs. Lack of impact of fruit weight on incidence of emerged nymphs, combined with a weak, inconsistent effect of fruit weight on feeding choice exhibited by early instars, suggests that the size of strawberry fruits as a food resource for early instars is not a significant component affecting their development or survival. Evaluating density and field impact of plant bugs for different cultivars under field conditions revealed that some host plant attributes affect the abundance of plant bugs, such as early fruiting season and high productivity. Decreasing number of emerged nymphs per fruit per plant with increasing density of fruits per plant suggests that females lay relatively more eggs per fruit on plants with few fruits; this pattern of oviposition may explain, in part, why patches with low density of plants typically have high incidence of damage. Planting a high yielding early season cultivar such as Cavendish may provide a line of defense against plant bugs, because fruits may escape damage in both space (dilution effect, with the impact of plant bugs being reduced when plants produce numerous fruits) and time (low incidence of damage early in the season).