Experts tackle readers’ garden questions.
Q: Every spring, silver beetles attack my roses. Years ago, they were only on white roses. Now, every color but red are covered daily. Nurseries say there isn’t anything effective. One year, I tried a trap tied to a tree and it made no difference. There are literally hundreds of them daily. They only last for a month and they are early this year so will be gone soon. I knock them off and squish them but would love to know how to prevent them next year!
Kay Schrudder, Fair Oaks
Master consulting rosarian Baldo Villegas: The silver beetles that Kay Schrudder is talking about are called hoplia beetles, and they are close relatives of the famous Japanese beetles.
Kay is right on her comments on these beetles. They usually show up for about six weeks in the Sacramento area. This year they showed up in the middle of April, and I expect them to be gone by the end of May.
They feed mainly on the petals of light-colored flowers from white to pink blooms. Control is difficult as they migrate from neighboring infestations.
Insecticidal sprays can be effective, but they need to be applied repeatedly to achieve control. However, these types of insecticides are not very selective and beneficial insects can also be killed.
Some control can be achieved by removing the beetles from opened flowers and either squishing them or dropping them in a bucket of soapy water. Birds such as scrub jays and other birds are great predators of hoplia beetles.
Baldo Villegas is a retired state entomologist and master consulting rosarian.
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