"It's a problem for farmers because the grubs feed on germinating corn seeds and roots in the spring, causing stand reductions," he says.
Asiatic garden beetle grubs are smaller than other grubs such as true white grubs and Japanese beetle grubs, Hammond says. The main characteristics to identify Asiatic garden beetle grubs are the enlarged maxillary palps on the side of their mouthparts, he says.
The problem with these particular grubs is that there really isn't much that can be done to mitigate them once they've begun feeding in the soil and causing stand reductions, Hammond says.
"Growers can scout their fields to see if they can find the pest and then use a preventive treatment of liquid or granule soil insecticides labeled for grub control in their fields," he says. "But the bottom line is that because this pest is so new, there isn't much data as to what insecticides are best to use.
"While scouting can potentially find grubs, that won't indicate if there is a problem. So growers who've had a history of unexplained stand loses should make sure they use a soil insecticide that has grubs on the label."
Hammond suggests that growers leave untreated strips to see what insecticides work best for their fields.
"None of the infested fields over the years appear to have been protected by the various seed treatments," he says. "Transgenic corn hybrids aren't designed for grub issues; all of these corn hybrids that were damaged last year had seed treatments on them that didn't do any good."
Growers with a history of unexplained stand loss may have to go with their field's previous history as the primary reasoning in deciding whether to use a soil treatment with insecticides, Hammond says.
"The grubs have to be managed prior to planting with a soil insecticide if growers already have them in the soils in their fields," he says. "Any kind of stand loss in corn hurts the yield.
"You can have a few bushel losses or up to a 30 to 40% yield loss, depending on how heavy or great the stand loss."