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Management Updates: Jul 13, 2016

More Dry Weather Insect Woes
Jul 13, 2016

And the (drought) beat goes on. We received a smattering of rain in the Amherst area earlier this week but not nearly enough to make up for all the evapotranspiration losses from the past several weeks. These dry conditions, as noted in an earlier post, make it hard to distinguish some insect activity from summer dormancy.

Be on the look-out for chinchbugs and billbugs, especially. They normally feed most aggressively in July and August, and the damage resembles drought stress. In fact, after I posted a similar comment a couple weeks ago, I received several e-mails from people, many of whom included photos of damaged areas and pictures of the guilty insects. So sadly, I was right - conditions are perfect for chinchbugs and billbugs to get established and do a lot of damage.

So again - monitor for chinchbug and billbug activity. Heavy chinchbug populations can be reduced with a pyrethroid. (If you are a golf course superintendent, remember that any application of a pyrethroid can contribute toward the development of resistance of annual bluegrass weevils to pyrethroids.) Billbugs are much more challenging to control once they reach the larval stages. Your best bet will be to manage the damage (raise the height of cut if possible, provide irrigation if possible) and make a note to take action next spring.

White grubs

Adults of all the white grub species (Japanese beetles, oriental beetles, European chafers, Asiatic garden beetles, masked chafers) have been flying for at least a couple weeks. Remember that dry conditions such as we are experiencing in unirrigated turf will force many females to delay egg laying until soil moistures increase enough for the eggs to survive. That means that we may not see new grubs hatching until a couple weeks (or more) later than usual.

Much of Massachusetts is currently 5 to 8 inches below "normal" for precipitation for the year, which translates to various levels of drought advisories. Many towns have already enacted watering bans, and the current forecast does not show much relief in sight. Keep in mind that insecticide applications that are made to target grubs really need to be watered in, but that may be really hard to do this summer. And remember that the neonicotinoids have some systemic activity, but the ability of the plant to take up the active ingredient is severely compromised when the plant is dormant.

Annual bluegrass weevils

Many superintendents seem to have gotten through the first generation without major damage. My guess is that this is because the egg-laying period was spread out over several weeks, much longer than normal. Many years we have a single well-defined period of time (say, a couple weeks in early June) during which most of the first generation insects are large larvae, feeding heavily. So the damage they cause is very visible but does not last very long. But this year, the adults spread the egg-laying over a much longer period of time, which meant that at any given time a site might have about 33% large larvae, 33% medium larvae, and 33% small larvae. The total number of larvae might have been similar to other years but because they were not all big at the same time, the degree of damage was spread out.

Heads up, though! We are now heading into the second generation. Samples from golf courses in southern New England confirm that we have new adults fully capable of producing eggs for the next generation. The hot temperatures that are typical for July and August, coupled with moisture stress, put the turf under severe agronomic stress, so it does not take very many larvae to cause visible damage.

Now is the time to scout your hot spots regularly and carefully. Many superintendents are currently reporting high numbers of adults moving about on the short surfaces (fairways and shorter). You might consider spot treating those areas with chlorpyrifos to knock down the adult populations. Meanwhile keep at least one larvicide in your storage area so you can use that if some hot spots flare up.

Submitted by: Dr. Pat Vittum