Turf Pest of the Month: How to best mitigate potential billbug damage

What makes billbugs such a difficult pest for golf course superintendents to deal with? Doug Richmond, Ph.D., entomology professor and Extension specialist at Purdue University, says identification and monitoring to start with.

He says, unfortunately for golf course turf, the only real way to monitor adult billbugs is with pitfall traps.

“Nobody’s going to do that,” Richmond continues. “(Instead) you can soil sample for the larvae. The larvae will show up in the soil here in the Midwest, it’s usually sometime in the second half of June when you start to see larvae moving from the stems of the plants to the crowns and then into the soil.”

Even more unfortunately for golf courses, at that point, damage to the turf has already begun. According to Richmond, damage appears just as the larvae move from the crowns and into the soil. That means that the only way to monitor them is to dig holes and look for the larvae.

Either that or using the tug test after damage has occurred to confirm that it’s actually billbugs.

“You take some of the damaged tillers and pull those out, they will come out of the ground really easily,” he says, explaining the tug test. “They’re not attached anymore. They’re sort of severed at the crown, and the crowns will be shredded and packed with a really fine sawdust-like frass, which is from the larvae chewing on the crowns.”

Prevention

On the chemical front of prevention, insecticides with clothianidin and bifenthrin work well for hunting billbugs, and an application in the fall would protect courses in the southeast during the winter. Richmond also names Envu’s Tetrino as a potential aid in the fight against billbugs.

“We’re doing some experimenting and trials with (Tetrino) right now,” he says. “That’s something that, down the road, could be an aid for superintendents with billbugs.”

In the realm of cultural control, Richmond says that superintendents should provide proper mowing, fertilization, irrigation, thatch management and cultivation practices to promote healthy turf.

Another option for golf courses that might have upcoming renovation or regrassing projects is the use of high-endophyte turfgrasses. These grasses — including certain cultivars of perennial ryegrass and tall fescue — hold certain types of fungi that deter feeding from insects like billbugs.

“These endophyte-infested cultivars, if the rate is high enough, will provide the plant with fungal toxins that will essentially kill the billbugs,” Richmond says. “It’s a nice built-in defense mechanism for a golf course and its superintendent.”

A new challenger

Superintendents in the Midwest will usually see bluegrass billbugs, according to Richmond. As the name suggests, bluegrass billbugs target cool-season turf like Kentucky bluegrass. That has changed over the last several years with hunting billbugs, a species normally found in warm-season turf making its way into the Midwest.

This is partly due to an increased planting of warm-season turf further north because of its climate resiliency, according to Richmond. Hunting billbugs provide a different challenge for superintendents as they’ve been reported to cause damage not only in their larval stages but as adults as well.

Get out and stay out

Luckily for golf course superintendents who have faced and defeated billbugs in the past, it’ll take some time for them to return.

“If you get good control, they don’t fly, so they have to walk to new areas,” Richmond says. “Once you’ve established control, it’s usually going to take years for those populations to rebound or move back in from adjacent untreated areas.”

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