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Tuesday, October 10, 2017

Controlling Tiny Jumping Pests on Grapes

Q. This year my grapes are again infested with leafhoppers. Before the fruit came off, I used Safer insect killing soap approximately every 7 to 10 days. I kept them at bay for the first part of the summer. However, they are now infesting the grapes heavily. Since I took the grapes off, I have been alternating soap and pyrethrin every 5 to 7 days. 
Characteristic leafhopper damage on grape leaves.Notice the white spots on the leaf surface from feeding by this very small jumping insect.

A. Leafhoppers can be a huge problem on grapes grown in the Mojave Desert. They are often confused with other insects but if walking past your grapes and hundreds of tiny insects jump into your face, then they are probably leafhoppers.
            Once reaching large populations, adult leafhoppers are extremely difficult to control without hard pesticides. Hard pesticides are not “organic”. If you don’t start spraying early, these insects will be a huge problem later in the season and much more difficult to control.
Leafhoppers feed on the undersides of leaves. They leave behind black specks..poo...from their feeding. This can land on the grapes and make the fruit undesirable or cause some off taste on wine grapes during fermenting. This can be a problem on "organically grown" grapes.
            The key to effectively using “softer pesticides”, closer to organic types of control, is to look for the juveniles on the bottom of leaves early in the season. Use soft pesticides in rotation with each other and spray when the younger populations are on the rise.
            Softer pesticides are not necessarily “organic” but are safer for humans and the environment. These pesticides, used in rotation, include insecticidal soaps like Safer, neem oil, spinosad, pyrethrin and even horticultural oils when temperatures are cooler.
Closeup of leafhopper sent to me by a reader. Thank you! They are very small, maybe 1/8 inch long. Did I mention they jump? Right into your nose, eyes or mouth when you walk by the vines. A real pest when the populations are left unchecked. And leafhoppers can transmit diseases among vines.
            Rotating these pesticides means to use a different pesticide in your arsenal each time you spray. Begin looking on the bottom of leaves when grape berries are the size of large peas. Once leafhoppers are seen, spotcheck leaves every week. Remove leaves that surround the grape bunches very early. Very important for insect and disease control.
            Juvenile leafhoppers don’t look much like the adults. But adults will populate the undersides of the leaves with these “babies” quickly once they start. Inspect the bottoms of leaves weekly and spray if populations are increasing.
Extreme leafhopper damage to grapes when you stand back a bit and look at the vines.
            Use a different “soft pesticide” each time you spray. You may need to spray every week but this decision should be made after looking at juvenile populations. Remember, young ones are easier to kill than the adults.
            Non-organic, commercially grown grapes use hard pesticides. Hard pesticides knock problem pests back longer but are not as friendly with the environment, human consumption and other insects in the area nearby.
            “Softer” pesticides must be repeated more often. Use them in rotation. Check populations and look for the juveniles. Start spraying early when the juvenile population is building.

1 comment:

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