Xtremehorticulture

Xtremehorticulture of the Desert

Skeletonizers on Grapes a Late Spring Problem

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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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Concord Grapes Ravaged by Skeletonizers

1 Comment / grape leaf eaten, grape leaf skeletonized, grape leaf skeletonizer pictures /

Q. Over the past two days, my two Concord grape vines have been completely defoliated by a larva-like worm.  It is yellow in color with black bands around the body and a wider blue band at each end of the body. Is the vine infected and needs to be removed or can the grape vines be saved? The damage is done, but is there a preventative action I should have taken? A. This is the grape leaf skeletonizer, a dark blue black moth that lays its eggs on the underside of grape leaves. They usually begin laying eggs around April and that’s when control measures need to begin. Grape leaf skeletonizer adult. A blue black moth.             The egg hatches and out comes a larva, fitting your description. This worm or larva begins to skeletonize, or nearly defoliate the grape leaves leaving behind the veins of the leaf. Hence the name, grape leaf skeletonizer. Grape leaf skeletonizer larva or worm eating the surface of a grape leaf. This is not my picture but I can’t find who sent it to me so my apologies to whomever it was.             Control is pretty simple and effective with organic pesticides containing Bt or Spinosad. Sprays should be applied in April prior to egg-laying or just after.             If you follow my blog via my newsletter or my tweets on twitter, I announce when to make these applications like these ahead of time. Otherwise, just mark your next years’ calendar and make this application some time in the first two weeks of April, depending on the weather.             Make sure you spray the undersides of the leaves, not just the tops. The spray will work now as long as the larvae, or the worms, present. It doesn’t work on the adult moths. Your grape vine will put on new leaves to replace the damaged one so just be patient.

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Grapeleaf Skeletonizers Flying Now in Las Vegas

2 Comments / grape leaf eaten, grape leaf skeletonized, veins remaining /

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.

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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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