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Sunday, June 19, 2016

Getting Rid of Leafhoppers

Q. What is the best way to rid the garden of leafhoppers? I have read that worm castings are effective (over time) in eliminating aphid and white fly infestations - is it effective on all insects that suck plant juices?

A. Once leaf hoppers have matured and they are hopping around a lot when you pass by them they are difficult to control without conventional "hard" pesticides.  About the only organic method I know of that does a pretty good job controlling leaf hoppers is Spinosad. Soap sprays may also work but I have not tried them when they are young. We are talking when they first come out, in April or May, well after bloom and fruit set.
Leaf hopper damage on grape leaves

However Spinosad has to be applied when leaf hoppers are immature in the nymph stages. It never totally eliminates them but reduces their numbers considerably if they are applied early enough and the sprays are directed where they are living. As an example I have used Spinosad sprays in about May on grapes to reduce leaf hopper numbers. 
Variegated leafhoppers and leafhopper poo-poo (the black specks)

I apply the spray about one week apart for 2 to 3 applications as soon as I see the nymphs on the undersides of leaves. I direct the spray upward so that the bottoms of the leaves are covered and then I repeat the spray on the tops of the leaves as well. To my knowledge worm castings have no effect on any kind of insect pests or beneficials. Treat it just as you would compost.
Spinosad by Monterey chemical

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