They seem to arrive earlier each year, feast on our rose blooms in ever-greater numbers and leave later and later. But whenever they arrive and depart, and in whatever number, they're ugly pests that can do quite a bit of damage to the petals of rose blooms, particularly those that are white or light-colored.

The good news is that they're usually with us for no more than six weeks or so. The bad news is that these six weeks fall right in the middle of our spring flush of blooms and that of course coincides with the spring rose shows in southern California and Arizona

Although there are various products that reportedly can be sprayed on the blooms to kill the beetles, it's difficult to reach these pests as they bury themselves deep within the petals. Also, most of the insecticides do little or nothing to deter new hoplia beetles from taking the places of their dead brethren, and some of these products can be phytotoxic, meaning that they can damage the foliage of your roses Also, the use of broad-spectrum insecticides may also kill insects that are beneficial to your roses.

So what can you do about the hoplia beetle? The response most often given is that you need to pick them out of the blooms one by one and drown them in a pail of soapy water or simply crush them. These aren't elegant solutions, particularly if you have a lot of roses, or if you dislike picking through your blooms and removing nasty critters, but they're probably your best bet if you want to try to control the population of hoplias in your garden.

There's an excellent overview of the hoplia beetle on Baldo's web site and another helpful summary on the University of California Statewide Integrated Pest Management Program site entitled: How to Manage Pests – Pests in Landscapes and Gardens: Hoplia Beetle.

There's an amusing comment in the UC article:

"When planting roses in an area where these beetles are plentiful, consider choosing darker-colored varieties such as red roses to help avoid problems with this pest."