Welcoming Weevils?

For many years we have applied a selective post-emergent herbicide in late fall for the control of Poa Annua on the tees and fairways.   The product has a reputation for being most effective when the weather's bad--basically, the worse the winter, the better this works.  Therefore, given how harsh this past winter was, it was somewhat surprising to find more Poa in the fairways this spring than we've seen in the past. 

There are a few options for controlling Poa in fairways, including the use of other selective herbicides, or plant growth regulators.  But what about trying a biological control?

One of the biggest insect concerns on golf courses in the northeast is the Annual Bluegrass Weevil.  With Poa (Annual Bluegrass)  being the predominant turf species on the greens, we must guard against this damaging insect.  However, on fairways we may welcome weevils as they can potentially help keep the fairways clean of Poa.  


Weevils have damaged the Poa in the fairway. 

Here's the plan:  We spray plant protectants on the greens to prevent weevil damage and do not treat the fairways, allowing the weevils to selectively remove the small amount of Poa we have.

Well, that sure sounds simple and easy.  Here's the catch--while Poa may be the preferred plant for weevils to wreak havoc upon, once the Poa is gone, they don't hop on the bus and head to the course down the street.  So, despite their name, Annual Bluegrass Weevils can damage Creeping Bentgrass.

Thus the plan becomes a bit more complex:  Allow weevils to munch on fairway Poa, but don't let them get so out of  control that they start damaging the Bent.   

In order to do this, we have allowed weevils to work on the Poa in fairways throughout the spring.  The damage to the small amount of Poa we have has been welcomed.

However, now that we're in the summer heat, we don't want weevils adding to the stresses that the Bent turf goes through.  We will now apply a plant protectant to the fairways in order to keep the weevils from working their magic on the Bentgrass.

As the year progresses we'll see if allowing this limited weevil activity truly helped keep Poa out of the fairways, while protecting Creeping Bentgrass.

At only 1/8" in length, the weevil larvae resemble a grain of rice.