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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).
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