HWA IPM considerations

Alright, I'd like to hear your management tactics for the following property, I'll list mine after the description.

Roughly 15 middle aged hemlocks ranging anywhere from 35 - 55' in height (combined diameters of ~100"). Plenty of shade from mature oaks, LOTS of HWA and scales. Damage has caused folliage loss upwards of 50% in most of the trees. Thin layer of clayey soil with lots of fine absorbant roots, beneath the clay for the most part is rock, or rocky subsoil. The new owners of the property have planted roughly 20 - 30 young hemlocks under and around the infected material during the summer. These young ones are no more than 6' in height and have already become infected with scale and HWA. Customer would like to not only see the new material thrive, but would like to try to save the sickly ones.

Site concerns are surface runoff going into the lake which is within about 200' of the trees, and then of course drift to neighboring properties and non target plants. Customer would like to stay as organic as possible.

What I did was a soil injection for the larger trees with imidacloprid within the recommended rate, and then an oil spray at 2% on the new material, or anything under 10' in height.

What do you guys think?
 
Sounds right. Imidacloprid is only contraindicated for water less than 25' away, so 200' is no problem. It's also very immobile in soil, so leaching shouldn't be a problem.

The only problem I see is the smaller trees taking up some of the imidacloprid, thereby reducing the overall availability to the larger trees. It will take a while to see results on trees with 50% foliage loss, but I've seen it happen quite a bit.

The oil spray will have to be repeated next year, but it should do well, too.
 
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