Every year from late July to early August, I often hear an approaching green fig beetle before I see it. It sounds like a Valley Carpenter bee, an insect I really like, so I usually pause and look around, but more often than not this time of year, the noise is a fruit beetle on the hunt for fruit or a nesting spot.
As a child, I enjoyed catching these beetles, which very likely was the beginning of my fascination with insects. They seem to aimlessly fly around, bumping into buildings, garden structures, and even people, making the beetles appear to be either blind or stupid. They are actually trying to locate garden fruit not by sight, but from the odorless gas emitted by the ripening fruit.
Our yard is a popular spot for the adult green fruit beetles because there are lots of available food sources this time of year with the grapes, peaches, and nectarines. In addition, the mulch and compost make ideal nesting spots for them to lay their eggs. I should be grossed out by the grubs in the compost, but the chickens relish the larvae, and it means more free protein rich snacks for the chickens next spring. The adult fruit beetle is a large green and tan metallic beetle (1.25 inch long) with a scarab shape, just like in the Egyptian artwork of other dung beetles and scarabs. The larval stage is a C-shaped, white grub, that feeds on decaying organic material in the soil, piles of manure, compost, or lawn clippings left in a pile.
I have tried for years to figure out exactly what our pretty green beetles are because local gardeners call them by so many different names, and I enjoy taxonomy of plants and animals. I have heard some folks mistakenly call them Japanese beetles (which is a completely different beetle, Popillia japonica, and is generally an east coast pest that feeds on lawns in the larval stage. According to U.C. Davis, these shiny green beetles are commonly called Green Fruit Beetles or Fig Beetles/ Figeater Beetles.
There is much debate in the scientific community about the exact species we have locally. It is definitely in the Genus Cotinis, but whether or not it should be called coninis texana or cotinis mutabilis, is where the debate remains. Genus Cotinis – BugGuide.Net The adults are definitely a pest insect in the garden, despite the larvae being a yummy chicken treat. The grubs are actually beneficial in a compost pile helping to break down the organic matter, but they are usually discouraged by gardeners because of their awful looking appearance and the damage caused by the fruit eating adults.
Adult beetles eat soft fruit such as tomatoes, grapes, peaches, nectarines, plums, figs, and apricots, causing substantial damage in some cases.
Trying to completely control them is pretty futile, but there are a few organic management techniques to deal with them. The adult beetles will find our garden fruit from a distance by flying in, even if I eradicate every grub in our yard. There are a number of homemade traps like a sweet juice (try grape or peach) or molasses in container with a cone shaped entrance. It will trap and drown the beetles. Harvest fruit early and keep fallen fruit cleaned up. For the grubs, some of the methods include: turning compost frequently to heat it up, flood it for a few days (wasteful in this drought), or open the compost to the chickens to go through. The chickens will pick out every last one. If you don’t have chickens, pick them out by hand when turning the pile, drop them into soapy water to drown or squish and put back in compost. Hey, I know it is gross, but it’s is better than spraying uselessly with poisonous chemicals!