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Management Updates: Jun 24, 2016

Insects: Dry Weather Adding Challenges
Jun 24, 2016

Dry weather adding challenges

Many areas in New England are facing moderate drought already, with rainfall totals for the year running 3 to 6 inches below "normal". This may well have an impact on turf insect activity, at least until we see some steady restorative rainfall.

Chinchbugs prefer sunny areas with soils that drain well, along with plenty of thatch. They can feed on any cool season turfgrass, and are often found on creeping bentgrass that is maintained at lawn height. (While bentgrass is not normally a preferred species in lawn settings, there are some native bentgrasses that seem to thrive in lawns. Sadly, I have some in my own lawn.) Bentgrass in a lawn-type maintenance tends to be very thatchy, providing plenty of "safe haven" for the chinchbugs.

Chinchbugs are usually active from early June through mid September, with adults and immatures active at the same time. Chinchbugs go through gradual metamorphosis, which means the immature stages ("nymphs") look just like the adults and feed in the same way - using piercing and sucking mouthparts to extract nutrients from the plants. As soon as you see evidence of chinchbug feeding activity, you can get some relief by applying a pyrethroid to the affected area. Most of the other common turf insecticides either do not have chinchbugs on the label or only claim "suppression", whatever that means.

Adults of white grubs are becoming active in many parts of the region. European chafer adults are flying now in some of the more southern areas of New England, and I expect they will be noticeable in the Mid Coast Maine area soon. European chafer adults are nocturnal but you often see flights emerging around twilight, and sometimes huge numbers of adults are attracted to a wide range of shade trees. While I have not had reports of it yet, oriental beetles are probably flying now. (They fly both in the day and at night.) And Japanese beetle adults will be flying very soon. We usually consider July 4th as the time when we become aware of the beetles, but they should start showing up in Japanese beetle traps within the next few days. They fly readily during the day, especially sunny, warm days, so don't be surprised if you see some on Sunday or Monday!

If the dry weather continues well into the summer, beetles of many of the white grub species may delay egg-laying. The females are able to detect when soil moistures are very low, and instead of laying eggs "on schedule", they will hold on to those eggs until soil moisture conditions improve. If this happens, the normal window for application of a neonicotinoid (mid June to early August) may be too early to achieve good grub control. It is too early to tell whether this will be the case, but stay tuned!

Also keep in mind - if you are planning to use a neonicotinoid as a preventive treatment against white grubs, you normally are counting on some of that active ingredient to be taken into the plant (taking advantage of the systemic nature of the neonicotinoids). But if the plants are in summer dormancy as a result of low - or no - rainfall, they are not able to take up the active ingredient.

Annual bluegrass weevils are completing the first generation even as I type. We are seeing new adults at most of our study sites, and they will be mating and reproducing within the next week or two. We refer to "new" adults as callow or teneral. The easiest distinguishing characteristic is that the adults are a yellow-tan color and very soft-bodied for the first 24 hours after they emerge. Then they gradually turn darker, passing through a reddish brown color and the body hardens up. Within three or four days after emerging from the soil, the body is quite dark in color. But new adults will clearly have a lot of scales on their thorax and hind wings, while older adults will be more shiny because a lot of the scales have rubbed off over time.

I dissected about 50 adults that we collected earlier this week (at a site just east of Springfield, MA). About 60% appeared to be "old" adults, ones that overwintered and are just now winding down. Many of those "old" adults were mature and still had a few eggs (or well developed testes in the case of the males), and some of the females appeared to have completed their egg production. Most of the "new" adults were sexually immature (as I would expect), but true to form, the weevil continues to throw curve balls at us. One of the adults that was still reddish-brown, so presumably was only a few days into its adulthood, was fully mature. Good grief!!!

While it looks like many people got through the first generation with little visible feeding damage, I would not let down my guard. For some, the first generation is not yet done, and the larval feeding will coincide with the hot, dry weather that is forecast for the next week. The summer weevil activity is often very difficult to characterize or predict, as we will no doubt be seeing small larvae, medium larvae, large larvae, pupae, and adults all at the same time. Some products work well on adults, while others are strictly larval products, so you will have to monitor aggressively and know which stage is dominant at any given time.

The dry temperatures we are experiencing will complicate matters for superintendents. The dry conditions will mean the turf is already under considerable agronomic stress. That means it will not take very many larvae (maybe as few as 10 or 20 per square foot) to weaken the turf further and cause visible damage. So be vigilant. If anything looks like ABW damage, get down on your hands and knees and take a closer look. Like so many things, early detection is the first line of defense.

As I have said several times already this year, it promises to be a challenging summer for ABW management.

Submitted by: Dr. Pat Vittum