Type your question here!

Monday, April 9, 2012

Borers in Fruit Trees and Buggy Grapevines

Q. Through the years I have planted many fruit trees and lost many to borers especially stone fruit trees. My grape vines have been devastated by whiteflies to the point where I could not harvest one healthy grape leaf last season. I have tried soap water but to no avail. Also, I have tried Lindane against borers but their work keeps appearing on my plum trees.

A. Whiteflies can be a difficult problem. We have not experienced whiteflies on grapes. The closest insect which might be confused with whiteflies, and is a common problem on grapes, are leaf hoppers.
Please make sure you are not confusing whiteflies with leaf hoppers because the treatment is very, very different. Whiteflies are like dandruff and usually fly in a cloud of small white insects when the leaves are disturbed. They usually leave a sticky substance on the leaf surface from feeding.

Click here to see some Whitefly pictures

Leafhoppers on their backs, maybe 1/8 inch long
Leaf hoppers on the other hand jump and are brown in color but they can accumulate in thousands on grapes and jump in your face, your nostrils and eyes as you pass the grapes and disturb the foliage. Both are nearly the same size but whiteflies are white and fly more delicately while leaf hoppers jump and are brown.
If soap and water sprays are used religiously on the grapes when these insects are small it should give fairly good control. If soap and water is delayed until they are mature adults, then control is probably iffy at best.

Whiteflies are listed on the University of California and pests lists for grapes but not a common pest.
Leafhopper feeding damage on grapes
Click here to learn the Common Pests of Grapes

If they are whiteflies then sprays such as pyrethrins might be a good choice but the label must include grapes if you are to use it within the law. If these are leaf hoppers, then sprays applied in May such as spinosad might be useful when this insect is still juvenile. In both cases when these insects are adults they are much more difficult to control.

Sap oozing from cut limb of plum
Regarding the borers in your plum tree, Plum can be attacked by boring insects but it is not as common as some other fruit trees like peach, nectarine or even apple. Please check and make sure that this is in fact borers causing damage and not just sap oozing from a stressed out tree. When plum is stressed from water, intense sunlight or heat stress they will ooze sap.

There is no insecticide you can use on fruit trees once they are attacked by boring insects and still safely eat the fruit in my opinion. Most insecticides recommended after fruit trees have been infested are usually systemic in nature. This means that the insecticide could also be in the fruit, not just on the surface.

1 comment: