If you grow light colored flowers, you may have noticed this lovely little critter chewing holes in them in the spring. How sweet of them.
This little pest is the Hoplia beetle, and the damage they inflict is really dependent on the plants you grow. This particular bug seems to be mostly attracted to light colored flowers, especially white and especially roses. They don’t chew on foliage or roots of most plants, but will bury themselves deep inside your blooms and start munching down, not just on the petals but also on the base — you know, the part that forms future fruit!!
They may also chew on young leaves and fruits of almonds and peaches — not surprising since they are closely related plants — and also grapes. Since these are all prominent crops grown in California’s Central Valley and that’s where I live, it is not surprising that I have them in my yard every spring.
If there is any upside to the Hoplia beetle, it is that they come around for only a short period of time in the spring. They have only one generation per year, so after they have mated and produced eggs, they are done. I seldom see them in my yard after the beginning of June. The problem, though, is that the timing of their appearance coincides with blossom production of many tree and bramble fruits like peaches, apricots, plums, cherries, nectarines, blackberries, raspberries, and anything else related to them. Since these all have light colored blossoms, they are a susceptible target. With blossoms destroyed, there will be no fruit.
So what to do? Not much. Poisons are not really effective since they must be directly exposed, and of course you could be harming helpful insects that you want to keep more than you want to get rid of these. Most recommendations are to just hand pluck them from infested flowers. I usually pinch them between flower petals. You can also shake flowers over a bucket of very lightly soapy water, where they will drown. Regular checking of your more susceptible flowers and removal of the bugs will lead to smaller populations in the future. The eggs and larvae develop in undisturbed vegetation near food sources (in the Valley it’s apparently alfalfa fields that are a big culprit), so regular mowing down of grasses and/or weeds or raking of fallen leaves may also help.
Another proposed solution to reducing numbers of the Hoplia beetle is to place white buckets filled with dilute soapy water (like a few drops of dish soap) around your more susceptible plants. The idea is that the beetles will be attracted to the color and fall in where they will drown. The soap helps to break surface tension of water and prevents air bubbles from being trapped around the body of the bugs. I haven’t tried it myself, but I do know that we get several of these bugs in our swimming pool every year, so it is likely a viable option.
Really, your best bet for dealing with these is to have a yard that is also attractive to insect eating birds. They will pluck the beetles out and pick up any that have fallen to the ground. The beetles themselves are kind of slow and fat, but they can fly when needed. Birds usually don’t have a problem catching them, as a result. A yard full of diverse plants will be attractive to birds and you won’t even have to pay them for their services!