Our sod producers along the coast have reported the first sightings of Japanese beetle activity this week. We have yet to see high numbers of Japanese beetles around the Raleigh area but I am expecting numbers to pick up drastically with the next substantial rainfall event. Over the next six to eight weeks, female beetles will be mating and laying eggs in lush, dense stands of turfgrass. Female beetles prefer to lay their eggs in areas with high moisture to ensure egg survival. The eggs will soon hatch into larvae commonly known as white grubs.
White grubs are capable of inflicting considerable damage to turfgrass by chewing off the root zone. The grubs will reach their most destructive point later in the fall when the turf is more susceptible to feeding damage due to drought stress. Feeding damage will appear as dead patches of turf that can easily be pulled back like carpet revealing the grubs. Over the past three years we have conducted extensive trapping across the state and have found that Japanese beetle flight peaks around the July 4th holiday. Peak flight indicates that the majority of the beetle population is active. This timing is used as a target for application of preventive grub insecticides. If white grubs are a perennial problem for your turf you may want to consider preventive treatment to keep your turf grub free in the fall. If your grub problems are more sporadic you may want to opt for a wait and see approach and target grubs with curatives such as Dylox or Sevin in the fall.
In the past few years we have seen a flurry of new products labeled for preventive grub control. Current preventive grub treatments include: Acelepryn, Arena, Allectus, Aloft, Meridian, Merit, and Mach 2 along with several generics. If you are planning on putting out a preventive grub treatment in the following weeks whether it be a granular or a spray, be sure to water it in to reach grubs feeding beneath the thatch!