Kill Bill(bug): Activity in Turf and a New Insecticide Option
|Four species of billbugs have been found in the Intermountain West: Bluegrass billbug (A) is the smallest and most abundant; Phoenix billbug (B) is identifiable by the dark M on the thorax; hunting billbug (C) is identifiable by the Y and parentheses markings; Rocky Mountain billbug (D) is the largest species with deer hoof prints on the wings.|
Linear pitfall traps are used to monitor billbug activity in turf.
Billbugs (Sphenophorus spp.) are a primary pest of turfgrass in the Intermountain West. Young billbug larvae feed within turf stems and mature larvae feed on roots, causing a tan to brown discoloration resembling drought-stressed turf, and sometimes plant death. Although the adults do feed on turf blades, the majority of damage results from larval feeding.
Most of what we know about billbugs comes from research from the eastern U.S., and we have found many differences in our region. In the Intermountain West, there is a complex of three species that occur simultaneously, including the bluegrass, hunting, and Rocky Mountain billbugs. In some isolated spots, the Phoenix billbug represents a fourth species. In other regions of the U.S., only one and sometimes two of these species will be present as major pests.
The eastern U.S. degree day (DD) model predicting billbug activity does not appear to be a good fit for the Intermountain West. For example, first occurrence of billbugs in Logan, UT in 2014 was on April 12 (60 DD after March 1), more than one month earlier than the eastern model predicted, which was on May 25-31 (280-352 DD). (Degree days can be obtained at the Utah TRAPs online tool).
Recognizing these differences from the eastern and western regions is key to improving management strategies. One way to be effective is to monitor. Installing and monitoring pitfall or linear pitfall traps aids in determining when the billbug adults are active in the turf.
In 2014, we monitored billbug activity on two golf courses near Boise, ID and one each in Logan and Draper, UT, and found that bluegrass billbug was the dominant species, making up more than 50% of the total trap catches. The next most abundant was the hunting billbug at around 35% of total trap catches, and Rocky Mountain billbug was the least abundant. Peak capture of adult billbugs occurred from late May to early June. Based on observations in 2013 and 2014, peak activity for the region has been around 400-600 DD. Billbug egg-laying coincided with peak adult activity and larval stages were most abundant a few weeks after adult peak activity.
Appropriately timed insecticide applications early in the season have been successful at suppressing newly emerged and young larval stages. The options include the neonicotinoid and diamide classes of insecticides that have systemic activity. Turf managers will be familiar with the neonicotinoids (Arena, Merit, and Meridian) and Acelepryn, a diamide having a mode of action that leads to muscle paralysis and death of the insect. Registration of Ference, a new diamide insecticide from Syngenta, was made available in August 2014 and has shown good results in suppressing billbug larvae.
These materials were tested in northern Utah and Idaho to determine optimal timing of these products in the region.
- Neonicotinoids, namely Meridian, should be applied between May 1 and mid-June.
- Acelepryn, which has very low water solubility, should be applied 2 to 3 weeks earlier, starting in mid-April.
- Although Ference has a similar chemistry to Acelepryn, it has a higher water solubility so that it should be applied at a similar timing to neonicotinoids. Ference also has a shorter half-life and persistence in the soil than Acelepryn.
Keep in mind that the recommended timing provided above is a guide and that weather and location can shift the dates. Colder winters and springs will mean later billbug activity while warmer winters and springs may result in earlier activity. Monitoring and becoming familiar with tools like degree day models helps to predict and anticipate pest populations.
- Ricardo Ramirez, Entomologist