Wooley Adelgid got my Hedge.
March 2, 2011 8:01 AM Subscribe
Hemlock hedge invaded by wooley adelgids. Should I try to save it?
We moved in in Nov. There is a 100' long hedge of hemlocks, well established, probably been there for 30 years. It offers a great barrier from the road, so we would love to keep it. Though a fence would do it, too. I have read all sorts of things about how to treat them, oils, chemicals, etc. Even consulted a forester. So, is the hedge worth trying to save? They will be need to be treated again and again. The bugs will probably come back via other hemlocks in the neighborhood. What is your experience?
We moved in in Nov. There is a 100' long hedge of hemlocks, well established, probably been there for 30 years. It offers a great barrier from the road, so we would love to keep it. Though a fence would do it, too. I have read all sorts of things about how to treat them, oils, chemicals, etc. Even consulted a forester. So, is the hedge worth trying to save? They will be need to be treated again and again. The bugs will probably come back via other hemlocks in the neighborhood. What is your experience?
We have a single tall hemlock with woolly adelgid, and were told the same thing you were, that they would need to be treated again and again. The tree guy, who would have made money from us choosing repeated treatments, advised us to cut it down.
posted by LobsterMitten at 4:35 PM on March 2, 2011
posted by LobsterMitten at 4:35 PM on March 2, 2011
Double-checked with my friend... He said he wished he hadn't cut them all down at once.
posted by ObscureReferenceMan at 5:41 PM on March 2, 2011
posted by ObscureReferenceMan at 5:41 PM on March 2, 2011
The pathogenic triangle. Let me show you it. Check principle 2 in this link.
Long story short, pathogens (and insect pests) are always present. They manifest themselves as disease or become problematic when the host plant suffers from some environmental stress. One thing is that plants age, and can become vulnerable to disease in maturity. You might want to see if there are other environmental changes - change in sunlight/shade, drainage, root damage (often caused by construction), etc.
Another factor is that Woody Adelgids are not native - so they don't have a "natural" predator. Some local natives such as ladybugs may eat them, but there's nothing like the co-evolved predator to keep runaway populations in check.
The conventional wisdom is that once plants begin to display disease, there is little you can do to permanently change the situation. That's why the recommendations to remove the plants. You can treat pests with oils, soaps, pesticides, even just washing with clean water - but as you already know, you'll just have to repeat the treatment again and again.
In my opinion, the best long term solution is to remove the hedge and replace it with something not susceptible to pest infestations. Your local nursery can advise you as to what works best. If you can't bear to do that, then treat with pesticides.
Note that pest infestations can introduce and aggravate fungal diseases as well, further stressing the plant - it's a slippery slope of decline.
posted by Xoebe at 10:35 AM on March 3, 2011
Long story short, pathogens (and insect pests) are always present. They manifest themselves as disease or become problematic when the host plant suffers from some environmental stress. One thing is that plants age, and can become vulnerable to disease in maturity. You might want to see if there are other environmental changes - change in sunlight/shade, drainage, root damage (often caused by construction), etc.
Another factor is that Woody Adelgids are not native - so they don't have a "natural" predator. Some local natives such as ladybugs may eat them, but there's nothing like the co-evolved predator to keep runaway populations in check.
The conventional wisdom is that once plants begin to display disease, there is little you can do to permanently change the situation. That's why the recommendations to remove the plants. You can treat pests with oils, soaps, pesticides, even just washing with clean water - but as you already know, you'll just have to repeat the treatment again and again.
In my opinion, the best long term solution is to remove the hedge and replace it with something not susceptible to pest infestations. Your local nursery can advise you as to what works best. If you can't bear to do that, then treat with pesticides.
Note that pest infestations can introduce and aggravate fungal diseases as well, further stressing the plant - it's a slippery slope of decline.
posted by Xoebe at 10:35 AM on March 3, 2011
This thread is closed to new comments.
A guy I know had his hemlocks diagnosed with the WA. And he cut them all down in one shot. I think he regrets that. He would have prefered to cut down one or two at a time, and replace them with saplings/small trees so that he would not have lost all the nice shade in one go. As I recall, his decision was mostly financially motivated - it saved him money to take tham all down at once.
posted by ObscureReferenceMan at 8:38 AM on March 2, 2011