Scouting for Annual Bluegrass Weevils

A new pest (new to us that is, but very common on the East coast) that is moving west into the Cleveland area is the annual bluegrass weevil (ABW). As the name indicates, it prefers to feed on annual bluegrass however, if it has no other choice it will feed on bentgrass. Last year we found a bit of ABW damage around the chipping greens and in some spots on the course, but it was very limited. A few other courses in the area had more extensive damage though, so it behooves us to keep an eye out for them. Besides just scouting suspected damage areas you can set traps to catch ABW as they exit their overwintering spots.

To help protect themselves from the cold, annual bluegrass weevil adults spend their winters in the leaf litter from trees. After they wake up for the season, they walk from the wooded area toward the shorter grass, where they prefer feeding. To monitor their activity levels we have set out Richmond linear pitfall traps, which catch the overwintering adults (if we have any) as they exit the wooded areas and let us know when populations are increasing and decreasing. Today I put out three traps in areas next to the woods and will check them three times a week. Below is a picture of one of the traps that is on the right side of #15.

As you can see it is a very simple trap, made out of a 2" piece of PVC pipe and a two liter bottle of Coke. We cut a slit into the top of the pipe and sloped it slightly toward the bottle, which has a bit of water in the bottom of it to keep the ABW in the trap. I will then pour the water through a colander and count the adults that are in the trap. By checking the traps a few times a week, we will be able to get a good idea of what the population levels are. When we feel the levels have reached their peak, we will spray an insecticide to eliminate the maximum number of adults and disrupt the life cycle.  

It is important to kill the adults because if we don't, then they will mate and lay eggs. ABW lay their eggs in the leaves of the turf plant, and when the larvae hatch, they eat their way down through the crown toward the thatch layer. Once the crown of a plant is damaged, the plant is dead. Therefore, to effectively control ABW, you need to kill the adults. There are also options to kill the larvae if we don't get great control from the application targeting the adults, but the ABW also has multiple generations a year (2-3 per year) so it is vital that the initial population is knocked down to avoid exponential growth. 

As stated in an earlier post, cold winters like we just had tend to kill off a lot of overwintering adults, so hopefully the ABW populations will be low this spring, but if they did survive, we will know as soon as they start exiting the woods. 

Ian