You Are Here: Management Updates 2009 Archive May 5, 2009

Date: May 5, 2009
Category: Insects
Subject: Annual Bluegrass (Hyperodes) Weevil

Annual bluegrass weevil applications in a rainy week
Many golf course superintendents in New England have been wondering whether they should be applying their insecticides this week for annual bluegrass weevil control. The plant phenology indicates the timing is perfect for many of the insecticides, as many areas in central New England are currently at Forsythia "half green - half gold" or slightly past that point. But as you no doubt have noticed, the forecast calls for rain every day this week with the possible exception of Wednesday.

So the question is - should you treat early in the week (5 or 6 May) or wait until it gets drier, perhaps early next week? The answer depends in part on what insecticide you are using.

The pyrethroids are virtually insoluble in water, so you could go ahead and use them as long as the soil is not saturated, and be quite confident that they will stay where you need them unless a torrential rain follows shortly after the application. (Torrential, in my mind, would be an inch or more less than six hours after the application.) The pyrethroids include: bifenthrin (Talstar™), cyfluthrin (Tempo™), lambda-cyhalothrin (Battle™, Scimitar™), and deltamethrin (Deltagard™), among others. The same is true for chlorpyrifos (Dursban™), which is still labeled for use on golf courses through 2009.

According to Dr. Chuck Silcox, product development manager at DuPont, chlorantraniliprole (Acelepryn™) appears to be pretty forgiving about water. The active ingredient is not very soluble, so we would not expect it to move very much even if heavy rain follows an application. Of course if the rain is heavy enough to cause surface run-off, the compound might move, but in light to moderate rains, Acelepryn™ should not move much. In addition, Dr. Silcox indicates that Acelepryn™ can be quite flexible regarding post-application watering. As long as the soil has decent moisture at the time of application, very little water is necessary after application - perhaps one or two spins of the heads.

Indoxacarb (Provaunt™) is less soluble than Acelepryn™ and it is not systemic. It binds strongly to soil organic matter and will not be moved very far into the soil profile, even by excessive rain or irrigation. Some readers in Pennsylvania and southern New Jersey may be getting ready to use Provaunt™ (which is best used to target young larvae), but those in the metropolitan New York area probably should wait for a few days before using Provaunt™. Hopefully by then the current stretch of wet weather will have passed. For those of you in central New England or further north, Provaunt™ should not be applied until at least two weeks from now.

Aloft™ contains bifenthrin (a pyrethroid) and Arena™ (chlothianidin, a neonicotinoid). Dr. Doug Houseworth, with Arysta LifeScience, has been urging applicators to delay watering in Aloft™ when targeting annual bluegrass weevils. His thinking was that leaving the material on the surface would give the chlothianidin more time to be absorbed through the foliage and the bifenthrin plenty of opportunity to kill the adults on the surface. However, when I posed the question to him, he indicated that the chlothianidin component of Aloft™ will work well regardless of when it is watered in. And my thinking is that the bifenthrin will not move very far, if at all, in the generally light to moderate rains that are forecast for this week.

All of us (Dr. Silcox, Dr. Houseworth, and myself) are in agreement - it is probably best to treat when the timing is right, even if the weather is not entirely cooperative. But do not apply anything if the soil is saturated and do not treat if it looks like you will get heavy rain in the 12 hours following the application.

Remember that Acelepryn™ is not yet registered in New York, but I understand that conversations are continuing between DEC and DuPont, and DuPont lists the registration as "pending".

Stay tuned for further developments.

Submitted by: Dr. Pat Vittum

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. The author and the University of Massachusetts are not liable for any consequences of any pesticide "recommendations". Mention of any trade name is not to be considered endorsement of a product.

Links followed by the symbol are external links that open in a new window.