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Management Updates: Apr 22, 2016

Spring Insect Update
Apr 22, 2016

White grubs

I received a grub specimen last week from near Amherst that appears to be a green June beetle larva. Green June beetles are quite common throughout the Mid Atlantic states but less so in New England. The larvae are a bit larger than European chafers (up to 1.5 inches long) and have very short, stubby legs. They feed on or near the surface at night, and often produce large mounds that resemble earthworm casts. Adults often feed on thin-skinned fruit. The life cycle is very similar to that of the Japanese beetle, with large larvae active in the spring before pupating. Adults will emerge in summer and lay eggs. (Adults are almost an inch long and a brilliant metallic green color.) The next generation of larvae will be active in August and into September, before moving down in the soil profile in preparation for winter.

Winter cutworms

Noctua pronuba, a relatively new introduced species, has become more common throughout New England in recent years. As the name suggests, the caterpillars are active in the winter (often feeding under snow cover). I received a report of winter cutworms causing damage in blueberries last week, which prompted me to mention to our turf managers that this is the time of year when large caterpillars may be noticed. They are nocturnal but you may see evidence of their nightly foraging - tracks in the early morning dew or new feeding. The caterpillars are usually a tan or almost pinkish tinge with a pair of dash marks (light and dark) on each side of each segment of the abdomen.

Very little is known about the life cycle of this insect in New England, but we believe the adults lay eggs in late August. If damage has been noticeable this spring, I would try to "manage the damage" for now, and not apply an insecticide. The larvae are almost finished with their development and will not be very susceptible to chemical control efforts. But make a mental (or physical!) note and consider treating the affected areas in late summer. Any product labeled for turf caterpillar control (e.g., cutworms, army worms, webworms) should work fine.

Annual bluegrass weevils

The Forsythia in the Amherst area have been at full bloom for almost a week now, and are beginning to show some green as the leaves begin to "pop". We collected adults from a golf course near Hartford earlier this week, and dissections show that several of the females are mature and contain eggs - but at least half of those females have not yet mated so if they were to lay those eggs, they would not be viable. (About half the males are fully mature, and the others will be soon.) Based on the development of Forsythia, many people in the southern part of the region will be well advised to apply an adulticide next week or early the following week. Once Forsythia hits that "half green - half gold" mark, you should be "good to go". (The degree day target is still being refined, but appears to be around 125 to 150 accumulated degree days, using a 50 degree base temperature.) But remember, when in doubt, hold off a day or two. While the adults clearly are on the move, there are undoubtedly many adults that have not yet reached the short grass. So if you treat too early, you will miss the "laggards".

Invasive craneflies

Many areas of southern New England are dealing with invasive craneflies. The primary species in this area is Tipula oleraceae, which has two generations per year. They overwinter in the larval stage (look like dirty brown, wriggly caterpillars but they don't have any legs). Those larvae will be completing their development soon in many locations. The pupal stage starts in the soil, but just before the adult emerges, the pupa is able to wriggle a bit and stick its tail end out of the turf. These "projecting pupae" look like twigs sticking into the air. Start watching for the pupa, especially on shorter heights of turf (fairways, tees). They are present in lawn settings as well, but not quite as easy to see. If you have experienced cranefly damage in recent years, you should consider treating for this next generation about two to three weeks after you see the pupae. (That gives the adults time to lay the eggs and for the eggs to hatch.)

Submitted by: Dr. Pat Vittum