COURSE CARE
No Matter What We Do, These Darn Things Are Still Here June 24, 2014 By Darin S. Bevard

Annual bluegrass weevil damage has been prominent recently on several golf courses. In this case, damage occurred on a pure stand of creeping bentgrass despite numerous preventative and curative control applications targeting annual bluegrass weevil.

Despite aggressive control strategies, annual bluegrass weevils have wreaked havoc in parts of the Mid-Atlantic region. Damage from annual bluegrass weevils and subsequent control has been a frequent topic of conversation recently. Damage to Poa annua has been widespread and despite the namesake of this critter, creeping bentgrass has also been affected. Superintendents are frustrated because preventative control applications have not been as effective as hoped and curative measures are requiring repeat applications to stop the spread of damage. Furthermore, many annual bluegrass weevil control programs that were successful in the past have failed to provide adequate control this spring and early summer.

Why is this so? There are many different theories, including resistance to control products, attempting to explain the difficulty in controlling annual bluegrass weevils this year. However, in most cases, the unusually cold spring likely contributed to the increase in annual bluegrass weevil damage. Colder-than-normal temperatures with intermittent periods of warm weather may have extended the period of adult annual bluegrass weevil emergence. Early adulticide applications may have controlled some but not all adults, and those that survived may have gone undetected and continued to reproduce. During recent visits the larvae, pupa, callow (immature) adult and mature adult stages of annual bluegrass weevil have been observed in the same area of turf, further complicating control. The best products to control larvae may not control adults and vice versa. The pupal stage is especially difficult to control with current products.

The early-season damage caused by annual bluegrass weevils may go unnoticed by golfers initially, but the impact of repeated control applications on the budget will not. Once annual bluegrass weevils are present, the expense of treating for them should be included in the annual budget. Although annual bluegrass weevil populations may fluctuate from year to year, they are very persistent. The bottom line is annual bluegrass weevils are nearly impossible to eradicate. The goal is to manage populations to keep damage to a minimum.

If your control strategies have been successful and damage has been kept to a minimum, consider yourself lucky. However, you should continue to scout for adult populations. As we have seen too many times this spring, assuming that control applications were successful without doing follow-up scouting can lead to major problems. Remember, annual bluegrass weevils are very small and can be difficult to detect. As a whole, annual bluegrass weevil damage has been worse than normal in the Mid-Atlantic region this year. 

Source: Darin Bevard (dbevard@usga.org)

Information on the USGA’s Turf Advisory Service

Contact the Green Section Staff  

More from the USGA