Adults and eggs of Brachyrhinus sulcatus (F.) were introduced into screened cages containing Concord grape plants. Eleven adults per cage produced complete defoliation and nearly complete fruit loss in the first season. The threshold of economic loss was 1–3 adults per plant per season. An index was developed for estimating root injury caused by larval feeding. Larvae fed first on phloem tissue producing girdled roots. The xylem was intact except in cases of severe injury. Vigor and fruitfulness over a 3-year period were not significantly affected by root injury.
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Wyatt W. Cone (1968) studied this question.