Starting in the fall of 2009, I had reports from a homeowner in Barrow County about millions of holes in her home lawn as well as huge populations of black beetles invading the outside of her home at night. Even after treatment from a pest control company, the insect did not leave. Winter temperatures drove the insect in the ground. However, this summer starting in early August, Barrow County has been invaded by “plague like” populations of these black beetles. We have also been visited by unusually high populations of grasshoppers andarmyworms. These little black missiles have been identified by Dr. Dan Suiter, UGA Entomologist, as Dyscinetus morator or commonly called a Rice Beetle (although no evidence has ever been produced that it actually feeds on rice).
They are roughly one-half up to three-quarters of an inch long and about 5/16 – 7/16 inch wide. The adults are nocturnal in their feeding and highly attracted to mercury vapor lights which would explain their habit of dive bombing parking lots at night. Once they are attracted to light at night, they stay until dawn which forces them to look for shelter (usually burrowing down in the soil or under any convenient shelter). They are excellent diggers easily burrowing down 6-8” in moist soil. If the lights are in a parking lot, then they’ll dig in at the soft spots where there are cracks or breaks in the pavement. They have also been known to damage asphalt shingles on roofs as they burrow looking for shelter.
Because they don’t necessarily overwinter in the same place, they won’t necessarily cause problems in the same place every year. There is no strong evidence of adult beetle feeding habits though their grubs are known to feed of grass roots just like the grubs of June beetle, Japanese beetle and chafer beetles. The good news is that their breeding is over for this year. We should expect two generations per year (late April / May and again in August). An emergence usually lasts for 1 -3 weeks. The beetles that emerged in August –September have laid eggs which will develop into larvae that overwinter until next April or May.
Unfortunately there is not a good control method for these Rice Beetles. To manage an emergence next spring, two things can be done. First, and most important, is light management. If it can be done, lights (some or all) should be turned off during the period that beetles are active. Or, lights on the building can be changed to those that are less attractive to beetles (yellow lights-never use mercury vapor lighting, unless you’re trying to attract the beetles). The problem with this partial solution is that the beetle mass emergence will likely be finished by the time the lights are changed. If lights must stay on, try altering the way they face or try relocating lights so that they’re away from, but still illuminating, the building. Another idea is to try a “bait” or “interceptor” light. These lights, and they should be a highly attractive light, should be placed in an area that attracts the beetles away from the building or from an area that’s trying to be protected, such as entryways into buildings.
Chemical treatments (sprays) likely don’t do much. If used, they should be microencapsulated or wettable powder formulations or any other formulation that maintains bioavailability of the insecticide. Treatments should be made around lights or in areas where beetles congregate (corners, lines along the intersection of a wall and flat surface); so that when beetles land they will be exposed to the insecticide.
A good publication on this beetle can be found at: http://entnemdept.ufl.edu/creatures/ misc/beetles/rice_beetle.htm As always if you have questions about the Rice Beetle or other pests of your farm, garden or home feel free to give us a call at 770-307-3029.
Britt West is the extension agent for Barrow County. You can reach him at firstname.lastname@example.org.