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Wednesday, April 9, 2014

Grapeleaf Skeletonizers Flying Now in Las Vegas

Q. My grape vine is started to leaf out. What is the spray I need to use to prevent the leaf eaters? I saw a black wasp like bug today (April 9)
A. That black wasp-like insect was actually a moth and does not sting. But she will be laying eggs on the undersides of grape leaves. These eggs hatch in a few days and the larvae that emerge will begin to consume the leaf from the underside, often times in a row, leaving the leaf veins behind. For this reason we call them grapeleaf skeletonizers.
Great picture of skeletonizer eggs and larvae hatching on the leaf underside from reader.
Also very good picture of adult by reader
Be careful of these larvae. If they land on your skin they will “burn” and give you a lot of pain. Use Bt sprays such as Dipel, Thuricide or Spinosad spray will also work. The sprays MUST be directed toward the undersides of the leaves as well as the tops. So plan on two passes over your grape vines; the first time on the underneath side and the second one over the top.

Spray the leaves enough to give the leaf surface a light coating on both sides. It does not have to be sprayed until the leaves are dripping wet. If you have a spreader/sticker to add to your spray then all the better and it will give you better and longer lasting control.

Both sprays will also control the hornworm which can consume leaves voraciously.

Leafhopper feeding damage to grape leaves. You will also see tiny black specks left behind (poop). These are tiny bugs that hop like a very tiny grasshopper but usually in the thousands on leaves.
Spinosad has the additional advantage of giving you some control of leafhoppers if those have been a problem in the past. The Bt sprays do not. Make two applications. One now and one more about a week from now.

1 comment:

  1. The first plan of attack should be to just remove the egg bearing leaf (or cut off a portion of the leaf with scissors if young plant with few leaves). New grape vines must be protected or they can be stripped of leaves and die. Established vines can take it, so allowing some predation is not particularly harmful. You can get 4-5 generations (amplification) produced in the summer. So early surveillance and intervention prevents the marching army down the road. While these skeletinizers have few predators be cognizant of the fact that predatory wasps will lay eggs on them (I think you will spot paralyzed larvae arched up similar to spinosad or BTK application) and virus infections (liquified remains). I usually leave these alone or move the leaf down into the underlying debris.