Xtremehorticulture

Xtremehorticulture of the Desert

Skeletonizers on Grapes a Late Spring Problem

Leave a Comment / fruit, grape, grape insecticides, grape leaf eaten, grape leaf skeletonized, grape leaf skeletonizer, grape leaf skeletonizer pictures, Grape leaves damaged, grape leaves eaten, grape pests /

Q. I have some pest problems on my grapes that I think is grape leaf skeletonizer, but it made holes in the leaves. Is this the same skeletonizer or do I have a new problem? A. The grape leaf skeletonizer is an adult three quarter to one inch or so moth which lays eggs in clusters and is a problem with grapes every year. The short-lived adult moth, along with the small eggs, don’t do any damage. It’s the larva which burn like matchheads if they fall on your skin. It’s these larvae that “skeletonize” grape leaves that causes all the damage. These young black and yellow larvae glide across grape leaves and turn these leaves into “skeletons” three to five times every year. Skeletonizing grape leaves is what gets them bigger. This can start from April or May of every year in Las Vegas depending on their populations. If you don’t get some control of them early with sprays of spinosad or Bt, their populations may continue to get larger and larger. There is another insect problem with grapes. That is the grape flea beetle which “chews” holes in the leaves. Most of the time it can be confused with “skeletonizers”. This is because they occur at the same time, but don’t create the same type of damage. Flea beetles chew holes in leaves. They don’t skeletonize leaves. And, unlike ‘skeletonizers”, they cause grape leaf damage, at the most, twice year. Oftentimes, just once in the spring. With “skeletonizers” the preferred spray is spinosad. You can use Bt (Bacillus thuringiensis) sprays and most of the time they will work. I like spinosad sprays because they will get leafhoppers as well which Bt does not. For grape flea beetles any insecticide works. But spraying them with an insecticide isn’t always the answer. Usually, unless the infestation is heavy, just waiting three weeks is enough. The population of grape flea beetles will pass without spraying. I oftentimes will just wait for three weeks but not for the skeletonizers. You must spray and spray early. Don’t forget to spray the undersides of leaves early.

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Watch for Grape Leaves Disappearing – Skeletonizer Flying

Leave a Comment / blue black flying insect, grape leaf skeletonized, grape leaves eaten /

Q. I just sited my first grape leaf skeletonizer moth. I’ve learned that Bt will control the worms.   I’d like to try and minimize the larvae if I can by eradicating as many moths as possible. Can you recommend the best course of action, if any, to control the moth itself? Grape leaf skeletonizer adult moth A. Not a lot of people know what they look like. They are a dark, blue-black moth that resembles a wasp more than a moth. I will post a picture of the moth, eggs and damage on my blog for all to see. If you have grapes, everyone should start looking for these guys. Grape leaf skeletonizer larva feeding ont he underside of grape leaf. This picture courtesy University of Arizona and can be found at http://cals.arizona.edu/yavapai/diagnostics/Assets/Images/Insects/grapeleafskeletonizer1.jpg             The adult only lives for about three days. Pretty much its sole purpose is to reproduce. The damage comes from the larvae eating the leaves, not the moth eating the leaves. The eggs are laid on the bottom of the leaf. The life cycle of the insect is about 60 days (two months). It takes about 7 days for the larvae to hatch from the deposited eggs.             I know you want to control the adult in an attempt to control the young but it probably is not the best approach since the adult will be hard to kill. Soap and water or insecticidal soap will work IF the soapy water comes in direct contact with the moth. But since the adult does not eat the leaves, you would have to actually spray the adults to kill them.             The larvae are fairly easy to kill since they eat grape leaves. You must spray it on the bottom of the leaves. Do this by pointing your applicator so it sprays up, on the bottom of the leaves. The Bt (Dipel, Thuricide) has about a one week residue on the leaves.             Spinosad will also work and has about the same staying power but is a little harder on bees.   A word of caution: These larva are nasty critters. If a larva falls on your skin it will feel like you were burned by a matchhead.

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