Saturday, November 2, 2013

November 2, 2013

Last Tuesday, October 26, we were visited by entomologists Dr. Albrecht Koppenhofer and his post doctoral research associate, Olga Kostromytska, from Rutgers University. The purpose of the visit was to collect adult annual bluegrass weevils (ABW)  to be used in a study to determine the degree of insecticidal resistance to products that are traditionally used to control their populations.

The annual bluegrass weevil, which feeds primarily on poa annua, is the most destructive insect that we battle with throughout the year. In the spring the adults emerge from their overwintering sites ( from under debris, leaves, dropped pine needles, etc) and migrate across the rough to greens, tee, and fairways where they lay their first generation eggs inside the sheath of its preferred host,  short cut poa annua. The eggs hatch and the larvae feed on the plant before tunneling out and entering the soil to pupate. This egg laying, feeding and tunneling in the poa plant kills the plant. In the soil they cause no damage, but become adults that will repeat this process. Over the year, up until October, there are multiple overlapping generations, before the adults head back to tree lines to overwinter. 

For each stage of its life cycle, a different insecticide must be used – a contact for the roaming adults, a systemic type for feeding larvae, and a soluble contact that can be watered into the soil to affect the pupae. That is complicated enough, yet what makes control even more difficult is that these weevils have been evolving to be resistant to many of these insecticides to the point that the products offer little if any control. In the end, the weevils are becoming harder to control and populations are growing, and damage is increasing. At courses with a long history of ABW, resistance is a serious problem. At the same time, the annual bluegrass weevil, which once was a threat mostly only to New England, is now evolving to thrive in the warmer temperatures of the Mid - Atlantic States and south.

At Greate Bay, we began seeing damage just four years ago. I suspect there is a degree of insecticide resistance because each year it has become harder and harder to control the ABW populations here. This year was especially tough. Two years ago we only needed to treat a few areas on the course, and were able to decrease the adult population enough so that subsequent applications were not necessary. Last year though, we needed to treat the entire course and then on certain fairways and most greens we had to follow up again with as many as three subsequent treatments. As late as early October, we were still noticing light damage on the greens, collars, and on some fairways. This sustaining population of ABW might be an indication that the insecticides we use are decreasing in efficacy, due to resistance

Dr. Koppenhofer had contacted the NJ Superintendent’s Association looking for courses that would allow him and his team to collect weevils for a study to determine resistance population levels throughout NJ and surrounding areas. Within a week after volunteering Greate Bay as a collection site, we had set up a date for his visit.

Sampling was simple. The researchers dug out small, 6-8” diameter pieces of sod, about an inch deep, in suspected overwintering sites along the tree lines of hole #7. The sod was placed in five gallon buckets of warm water and a paper towel was laid on the water as a raft for the weevils to hang onto as they floated up wards through the water. The weevils were then collected from the paper towel rafts and put in containers for their trip back to Rutgers. In all, they were hoping to collect at least 1,500 adults, which they did.

Our weevils, along with the ones from other courses taking part in Dr. Koppenhofer’s study, will be tested with various insecticides normally used to control them, and the degree of resistance, if any, will be determined. From this study, alternative treatments and/ or insecticide rotations may be recommended to decrease resistance so that in the future, we will be able to better control the ABW. 

Dr. Koppenhofer collecting weevils on #7

Annual Bluegrass Weevil