My petunias are horribly sticky - I assume thrips are in control although I have tried to keep them washed off (insecticidal soap) and sprayed with a systemic (orthonex). Is there anything else I might try? Would a dormant oil spray work, and if so when would I use it? Also, there are small worms that are probably chomping the blossoms. What would work to prevent or kill them? How do worms can get into my flower boxes, that are at least 6 feet off the ground?



Petunias exude a naturally sticky substance through their stems that also spread to the flowers.  Although no one knows for sure why this phenomenon occurs only in petunias, many botanists believe it is a defense mechanism to trap sucking insects such as aphids and thrips. Many gardeners find the sticky substance to be a nuisance and therefore do not grow petunias for this reason.  Breeders are working on new hybrid varieties that will not have this "problem".  But if this is indeed a natural process to ward of insects, the new hybrids may result in more a more sticky problem.

As for worms - if you are having leaves that are eaten, it could be budworm, which is a caterpillar of a moth and Bt, Bacillus thuringiensis is effective on controlling caterpillars.

Posted on 6 Aug 2008

Maggie Shao
Horticulture Agent, Salt Lake County

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