Q. My grapes leafs are gigantic this year after the big pruning; but something is taking big munching bites out of the leaves – I don’t see any thorn worms? Any ideas?
-Jeri
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| One of the hornworms as larva or caterpillar |
A. It is probably hornworms this time of year. Put on a spray of Bt now or spinosad. Repeat it in about two weeks. Use spinosad if you had leafhoppers last year. They are tiny and they jump. That should keep them pretty clean.
Q. I enjoy your articles in the newspaper. Thank you for your insights into my garden. I have a five year old grapevine. Each year I have an infestation of tiny white flying insects. I have tried traditional sprays with no success. What are they, and how do I get rid of them? BTW – The hummingbirds love them. The birds will cause the insects to become airborne, then pluck them off in mid-air.
-Fred
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| Leafhopper damage to grape leaf |
A. It is possible that they are either leafhoppers or whiteflies. I have seen leafhoppers more often than whiteflies on grapes. However your description fits whiteflies better than leafhoppers since you said they fly and are white.
Leafhoppers are usually darker in color, green or brown or a combination of both but jump into the air rather than fly. Both are hard to control but soap and water sprays are good when they are very young.
It is getting late now as this should have been applied in late April or early May if using soapy water. You can also use insecticidal soap. It is in the right concentration and does not have potential problems as you might have with soaps or detergents that have skin conditioners or scents added.
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| Leafhopper damage cropped and enlarged upper surface |
Be sure to spray the undersides of the leaves which is where they are most likely found but go out and find where they are and direct the spray on the insects, not just on the plants. The insecticidal soaps have no residual so if they land back on the soapy surface of the leaf it will not harm them.
The soapy water MUST come in contact with the insect or it will not work. If these are truly whiteflies then use a fruit spray that contains the words pyrethrums, permethrin, cypermethrin, pyrethroids, etc. you get the idea. It should have “ethr…” in words in the ingredients. There are lots of different kinds.
If this is leafhoppers you can try applying spinosad this time of year but it is starting to get late for this application. It should have been done in May but try it.
Hi Robert – I originally thought that I also had leafhoppers but now that you've mentioned whiteflies I'm not sure. What do you think? https://plaaant.com/plant/grape-on-arbor-1-from-south-ruby-seedless/57eed7b1bd707a0000bc29d2?noteid=59e754568a15d70000caa4ac#59e754568a15d70000caa4ac
I tried to access this URL but I had difficulty downloading the pictures you posted on it. I am out of the country right now and my download speeds are quite low. I will try it again a little bit later when the Internet is not quite so busy but I wanted to respond right away. I really like the selections I saw listed on your site. Very impressive. I hope you are posting what you're learning so that other people can benefit from your experiences. If you are, please send me a link. From my past experiences whiteflies are very different from leaf hoppers in their life cycles as well as control strategies. I would much rather deal with leaf hoppers than whiteflies. To me, whiteflies are like flying dandruff… They swarm when the leaves are disturbed but they are not as easy to excite and have them leave the plant as leaf hoppers. Whiteflies are lousy flyers but they do fly. Leaf hoppers don't fly at all but they can jump long distances compared to their body size so they appear to "fly" to some people who aren't paying close attention.There is some overlap on chemical control of these 2 insects but sprays of Spinosad will not work on whiteflies.I will post more here as a reply when I can get a better look at this picture you posted.
Thanks Robert! Yes to your question. One of the objectives of the website is to accelerate the sharing of information in a structured and objective manner. Let's chat when you're back from your trip. I'm in Phoenix AZ so not too far from you and similar growing conditions.
When you are comfortable with the website output and want to begin some readership please let me know. I will follow it and help people connect to it. I have quite a few readers living in your climate zone.