Impact of Taedia scrupeus (Hemiptera: Miridae) Feeding on Cluster Development in Concord Grapes

Abstract

Taedia scrupeus (Say) feeds on grape clusters and shoots early in the growing season. The impact of nymphal and adult feeding was assessed at the individual shoot level by confining nymphs within sleeve cages at 4 different times: prebloom, bloom, postbloom, and prebloom to postbloom. Prebloom feeding significantly reduced the number of berries per cluster and average berry weight, resulting in a 68% reduction in cluster weight. When nymphs were allowed to feed from prebloom to postbloom, cluster weight was reduced by 71%. Feeding only during bloom and postbloom did not affect cluster weight. Prebloom feeding reduced the number of florets per cluster, berries per cluster, and berry weight. The whole-vine impact of T. scrupeus was examined in a commercial Concord vineyard, where 3-vine experimental units were treated with carbaryl to remove T. scrupeus or were left untreated. Unsprayed vines, with a mean density of 20 T. scrupeus per vine, yielded 10.4 kg per vine, and sprayed vines without injury yielded 14.1 kg per vine. The yield component most strongly affected was the number of clusters per vine, which averaged 165.4 and 131.8 per vine in sprayed and unsprayed vines, respectively. Each T. scrupeus nymph was associated with 0.18 kg of crop loss, suggesting that as few as 0.5 nymphs per vine can cause economic injury. Where treatment of vineyards to prevent T. scrupeus injury is warranted, it must be applied during the prebloom period.