Beware of the other 
ash borer

I have a couple questions. First, are you advising folks to start using something on ash trees as a precaution against that new borer? If so, what do you recommend? I have some Bayer Tree and Shrub. Second, I have violets taking over my grass that I don’t want. Do you have any suggestions?

— Barbara

The borer you’re thinking of on your ash trees is called emerald ash borer. It’s not over here yet — it started in Boulder and has spread into Longmont and now Lafayette. Whitney Cranshaw, a professor of entomology at Colorado State University and the “bug guru” for the Rocky Mountain region, believes that the emerald ash borer will be limited by river basins. For now, it’s in the South Platte Basin and other parts of the state are unaffected. The truth of the matter is not if the emerald ash borer will get over here, it’s a matter of when. Hopefully, it will be 50 years, but it could already be here and we just haven’t identified it yet. For now, we’re alert for any telltale signs of the insect locally and trying to educate people on the necessity of not transporting ash nursery stock, especially firewood, from an infested area into an area that’s not infested. The belief is that most of the “leapfrog” spreads of this pest (it jumped more than 600 miles from Kansas City to Boulder) are due to people transporting firewood.

Having said all that, we do have a different borer that affects ash trees that’s always been here. It’s called lilac-ash borer. It’s been on the rise the past few years, which is normal — insect and disease pests have their highs and lows. Right now we’re on a high with this little monster. I think it’s advisable for people to be vigilant. If you see any dead branches on the tree, it’s probably due to lilac-ash borer. I’m not talking about little, dead, twiggy stuff in the interior of the tree — that’s normal. If you look at the tree from a short distance and see dead branches sticking out from the canopy that’s the call to action.

The time to treat for this borer is in the spring. The way to control it is with a spray of 38 percent permethrin. You need to spray well up into the tree, coating the bark of any branch 1 1/2 inches or larger down to the ground. The first spray is the latter half of April and the second is a month later. I’m afraid that the imidacloprid in your Bayer Tree and Shrub won’t work on this type of borer (though it will work on emerald ash borer).

As for your violets, they’re doing what violets do — spread with abandon! You can get rid of them with a bit of persistence. Spray the lawn area with Fertilome Weed Free Zone. It won’t hurt the grass, it only affects broadleafed plants. You’ll want to spray every couple weeks until they’re gone. Violets are a tough plant to get rid of and you really have to keep at it for it to work. If you let the violets recover, you’re just starting over.

A couple notes of caution, though. First, make sure that there’s no spray drift that might get on your good plants. You also want spray early in the morning to minimize any volatilization of the herbicide which might affect your plants. Secondly, the herbicides in this spray do have some soil activity and can affect surrounding desirable ornamental broadleaves if you’re not careful. When you spray, only spray enough to wet the foliage of the violets without soaking the soil. These herbicides can persist in the soil for several years, so over-application can lead the accumulation of the chemical, which can lead to damage or even death of surrounding plants.

Dennis Hill is the nursery manager at Bookcliff Gardens, Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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