This section of the web site features Management Updates written by the turf specialists of the UMass Extension Turf Program. The messages cover local problems, are geared toward local conditions, and are posted frequently during the growing season. The most current message appears below; click into the archive at the right to see previous messages. Join our free e-mail list to receive notification whenever an update is posted.

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Latest Message

Date: September 2, 2010
Category: Insects
Subject: Invasive Crane Flies, Sod Webworm, White Grubs

Webworms, crane flies, and grubs, Oh My!

As we enter September, we can hope the hot weather will finally break for good - and that Hurricane Earl will stay well east of Cape Cod. But late summer is the time when we can expect to see several turf insects in a variety of settings.

Invasive crane flies

A year ago invasive crane flies (the "marsh crane fly", Tipula oleracea) were confirmed on Martha's Vineyard and in Falmouth. You may still be seeing some adults flying in those areas. The adults look like giant mosquitoes. (Remember that there are also many native species of crane flies that fly at this time of year, so just because you see crane flies is not necessarily cause for panic.) The adults will be laying eggs soon. The eggs survive better in areas where the soil is moist - so if the hurricane drops a lot of rain in southeastern Massachusetts, that might increase the likelihood of those eggs surviving. The immatures (kind of leathery looking, often an olive green or gray color), will feed into November most years, and can feed through the winter months if temperatures are mild. They will complete their development next spring (sometimes as early as April), adults will emerge, and produce eggs for another generation.

There have been very few field trials conducted on this species of crane fly, but there appear to be many options. One approach is to treat affected areas just as larvae are hatching out of the eggs (likely to be mid to late September this year). Several classes of insecticides have been used with success in New York and Washington State, including neonicotinoids, pyrethroids, and the new insecticide from DuPont (chlorantraniliprole). Refer to the Professional Guide for IPM in Turf for Massachusetts for details. Follow the application with water, to enhance contact with the subsurface larvae.

Webworms

Right on schedule, sod webworm adults are flying in large numbers in my own back lawn. I always see the moths flitting about in late afternoon or evening at this time of year, when I am mowing, and I am always impressed at the large numbers of moths. But to date I have never seen any damage caused by the webworm larvae that would have been feeding in the previous two to three weeks. While some turf managers do experience damage from webworms during the summer, most areas do not experience populations that warrant treatments. Furthermore, as we are approaching late summer and early autumn, surely we will get a break from the beastly hot temperatures, and our cool season turfgrass should be able to begin to recover from this record-breaking summer.

White grubs

This is an excellent time to monitor for white grub activity. Because the summer was so hot and dry in most locations, you might find that grubs are more active in areas that retain moisture better (heavier soils, low lying areas, areas near leaky sprinkler heads). Remember that ordinarily European chafers do better in dry conditions than our other main species (Japanese beetles and oriental beetles). Also keep in mind that some Japanese and oriental beetle females may have delayed egg laying because soils were so dry in so much of the region. So you may see some fairly small grubs, along with the more typical second instars, in many locations.

For turf managers who must comply with the Massachusetts Children and Families Protection Act, it is really important that you monitor for grub activity NOW. Products that contain trichlorfon are often used to reduce early autumn grub populations but the law prohibits use of those products on certain school grounds and athletic fields. However, we conducted studies a couple of years ago and found that two of the neonicotinoids currently available on the turf market did reduce grub populations, even when applications were not made until mid September. The products did not lower grub counts nine days after application, but when we came back and looked 30 days after application, grub counts had been reduced significantly. The applications that "worked" were products that contained chlothianidin or thiamethoxam. Note that imidacloprid did not reduce grub counts significantly, even 30 days after the September application.

The message - if you need to rely on a neonicotinoid to reduce this fall's grub populations, the earlier you make the application, the more quickly it will work (and the more skunk damage you will avoid!). Remember to follow the application with at least 0.1 inch of water, 0.25 inch is better.

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. Trade names of materials are provided for informational purposes only and do not substitute for a thorough and careful reading of the label and application according to label instructions. 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.

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