The Usual Suspects for Turf Insects
& Research Results in 2013
Chinch bugs are active in the thatch layer and damage turf stems with their piecing-sucking mouthparts.
Hot, dry conditions in 2013 also flared mite problems.
The variety of turf arthropods diagnosed by the Utah Plant Pest Diagnostic Lab this year mirrored what was seen in 2012. In particular, chinch bug and Banks grass mite were among those unusual pests that were submitted to the lab for a second consecutive year. Light feeding damage from these pests resembles drought stress in a lawn, but with high chinch bug populations, the turf begins to die in irregular patchy areas. Heavy mite pressure can also kill turf, where the blades of grass turn brownish-yellow and become stiff.
The common factors of the past two seasons were warm springs and summers and drought conditions that favored both chinch bugs and mites. Drought-stressed plants often have amino acids and other nutrients that are more available to these arthropods compared to healthy plants. In addition, drought conditions can make for an unsuitable habitat for predators that feed on these pests. It is predicted that these climatic conditions will continue, leading to more occurrences of these pests in our region.
Billbugs (Sphenophorus spp.) are another problematic turfgrass pest in the Intermountain West. These weevils deposit eggs in turf stems, where the larvae hatch and begin to feed on plant tissue. Feeding damage causes severe discoloration of turf resembling drought stress, and in severe cases, can lead to plant death.
A degree-day (DD50) model, which is a tool to predict timing of insect emergence and activity, has been developed for billbugs in the eastern U.S. The model calculates degree days from daily maximum and minimum temperatures using a baseline development threshold of 50 F. Insect activity and development is, in part, dependent on temperature, so degree day models provide optimal treatment timing recommendations. Because temperatures vary among years, applications based on calendar date may be too early or too late, resulting in poor control of billbug larvae.
This model, which includes information for first occurrence of adult activity, timing of egg deposition, and duration of larval stages, has yet to be validated in the West. In 2013, we began to survey billbugs to determine their seasonal activity and to test the DD50 model, as a component of a USDA-Western Region Integrated Pest Management grant (#2012-03313).
Linear pitfall trap consists of a 1 m long PVC pipe with an opening (1 cm) along length, buried flush with soil surface.
Billbug adults are captured in a collection cup held in an irrigation box at one end of the pipe.
Golf course sites were selected from Boise, Idaho to Logan, Utah where major billbug issues had previously been reported. From May to October, with the help of University of Idaho Extension in Ada County, billbugs were surveyed in the rough at each course where billbug damage was suspected. Researchers used linear pitfall traps to collect ground-active adult stages and turf soil cores to detect the eggs and larvae in stems and soil.
The bluegrass, hunting, and Rocky Mountain billbug species made up the complex of billbugs found at all sites. Bluegrass billbug was the dominant species and composed 60% of the total trap catches, followed by the hunting billbug (34%), with the Rocky Mountain billbug being the least abundant species.
We compared billbug emergence with the existing DD50 model. It predicts that the first flight will occur between 280 and 352 DD50 after March 1. However, in 2013, we found the first occurrence of billbugs to be before 217 DD50 (May 15), about one week earlier than the current model predicted. We found that peak billbug adult activity occurred in mid-June (540-650 DD50). Billbugs deposited eggs from late May into early June just before peak adult activity and the damaging larval stages were most abundant in July.
This study will continue in 2014, where we will add additional sites around the Wasatch Front. Data from multiple seasons will be used to adjust and validate the DD50 billbug model to optimize timing of management in the West and to assess factors contributing to the variation in billbug populations (elevation, precipitation, temperature). It is clear that monitoring with traps is a useful tool, and once the billbug DD50 model is validated, both can be used to improve management practices, such as more efficient timing of prophylactic pesticide applications.
-Ricardo Ramirez, Entomologist and
Madeleine Dupuy, USU Biology graduate student
For More Information:
Kopp, K., R.S. Davis, and R.A. Ramirez. 2013. Chinch Bugs. Utah State University Extension. ENT-169-13PR.
Cranshaw, W.S. 2012. Clover and other mites of turfgrass. Colorado State University Extension. Fact Sheet No. 5.505.
Murray, M.S. 2008. Using degree days to time treatments for insect pests. Utah State University Extension. IPM-05-08.
Shetlar, D.J. and J.E. Andon. 2012. Billbugs in turfgrass. Ohio State University Extension. HYG-2502-12.