Another wave of cutworm damage

Cutworm emerging from a soap flush

cutworm feeding damage

There is another wave of cutworm damage at the moment on our research greens here at GTI. I am not sure if it reflects what is happening in other areas, but I thought I would post an update on it. What is remarkable is how much damage a single cutworm can do. We have observed lots of feeding damage and our soap flush in the area will only flush out 1 caterpillar. Insecticide applications should be made at night. The insect parasitic nematode Steinernema carpocapse is quite effective against cutworm. You might want to give it a try. The nice thing about them is that it is not a Class 9 pesticide that has to be reported on your PCP Application Form.

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Grubs have gone into hiding

A few samples of the grubs found yesterday

Dr. Michael Brownbridge, his gang and I marked out a site for a grub bio-insecticide trial yesterday. Granted, the site was a very sandy soil and it had not had much rain to speak of in the last couple of weeks. What we found is that the grubs have gone quite deep in the soil to where they can find moisture. In some cases this was as deep as 4-5 cm. Secondly, the grubs are still very small. Dr. Brownbridge put in a similar trial at the same time last year on this same site and the grubs were much larger at the same time last year. They are almost all in very early to mid-first instar.

So this brings me to my recommendation. Even though this is usually a good time for lawn care operators and homeowners to apply nematodes for grub control, if you are in an area that is not irrigated and has not received much rain and or you have sites with very light textured soils, I would recommend waiting until we get a good rainfall event before attempting to apply nematodes to control grubs. They are simply too far down in the soil and your chance of success is not good. There is still plenty of time to apply because as I mentioned the grubs are still very small. There is probably at least a two week window left to successfully apply nematodes for grub control. In some ways this is good news, especially if you are in an area that has both Japanese beetle and European chafer grubs. By waiting a couple of weeks there is a greater chance that all of the Japanese beetle adults will have finished egglaying and you will be better able to target both grub species with one nematode application.

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The good news and the bad news about insects

BTA adults under the GTI research green.

Let’s start with the good news. In our hairy chinch bug bio-insecticide trial we are now finding that about 90% of the chinch bugs are adults. This means that the damage that you are currently seeing is probably as bad as it is going to get. Once the chinch bugs become adults they feed very little and they are going to be concentrating on finding a nice protected hiding place for the winter.

There is also good news where black turfgrass ataenius are concerned. They are also at the end of their one year life cycle. The bulk of the damage showed up towards the end of July and the beginning of August. Here at the GTI, Peter Purvis is renovating half of a research green and when he cut and lifted the sod he found hundreds of adult BTA and only a very few grubs.

Now for the bad news. European chafer grubs have hatched and are mostly in the late first instar and early second instar. We are planning to treat next week for our nematode and bio-insecticide trial on European chafer grubs. So if we are treating, that probably means that those of you out there with clients with grub problems, you should be treating too. There are some complications in areas where the grub population is a mix of European chafer and Japanese beetle grubs. If you have an area where this occurs it is probably best to wait for a couple more weeks and treat in early Sept. to insure that all of the Japanese beetle adults have laid their eggs. Remember the best management practices for applying nematodes for grub control.

1. Purchase the correct species for the target pest (H.b. for grubs
2. Keep the nematodes refrigerated after purchase
3. Use within 3-4 weeks of purchase
4. Apply when soil temperatures range from 12-30 degrees C.
5. Water lawn until moist before applying nematodes
6. Use nematode mixture within 2-4 hours of mixing
7. Keep the nematode mixture well stirred.
8. Apply nematodes at dusk or on a cloudy day and water in immediately.

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