Part IV - Living Walls - Borders & Hedges: Yews and Hemlocks: Re: Re: Hemlock in these times?

» anewleaf - Re: Re: Hemlock in these times?

No bios known yet. But another chemical you can use is Imidacloprid. it is a bayer exclusive....in the tree and shrub insect control product. this is the same chemical as Marathon used in the greenhouse industry for whiteflies and fungus gnats and Merit used in the nursery industry for sucking insects...like adelgids, which are little more than living guts.

Application on large(all) specimens is simplified by the fact that it is applied to the soil under the tree, in the root zone in a water mix. one application in spring is good for a year. At first glance it seems a bit pricey, but considering its longevity its a pretty good deal.

The adelgids mode of attack is a bit curious. Typically the first attack is heavy and then nearly disappears as the hemlock responds with natural defences. Often a homeowner thinks they have weathered the storm- false security, I'm affraid. The few survivors tho are immune to the tree's defenses and wham, bam.... the second wave pretty much finishes the job on the weakened tree.

So far, my observations are that the imidacloprid seems to be effective as a repeat agent, but one can't rule out the possibility of adelgids developing resistance over time...so the best course seems to be to use it sparingly...once every two, three, or four years, which really ought to be effective.

-- posted by anewleaf