Answer: Adults as well as immature leafhoppers feed on the underside of leaves by sucking out the liquid cell contents. The tissue surrounding the feeding puncture turns pale white and eventually dies. Feeding injury shows up first along the veins but later the whole leaf is affected Feeding is limited initially to the lower leaves.
Grapevines can tolerate populations of up to 15 hoppers per leaf with little or no economic damage. However, heavy leafhopper feeding can result in premature leaf drop, lowered sugar content, increased acid, and poor color of the fruit. Ripening fruit is often smutted or stained by the sticky excrement ("honeydew") of the hoppers, which affects appearance and supports the growth of sooty molds. Also, severely infested vines may be unable to produce sufficient wood the following season. Damage to the vine can be serious if infestations are allowed to persist unchecked for two or more years.
Diazinon, Imidan or Sevin are registered for leafhopper control on grapes. Be sure to follow label directions. Repeat sprays may be necessary.
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