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Hemlock Help - Wooly Adelgid

Posted by bergenjersey (My Page) on
Wed, Jul 2, 08 at 13:26

I have a hemlock that suffered some damage from wooly adelgid. I sprayed it recently with ortho volck oil spray.

A few days before application I hosed down the tree. I'm going to try and do that every week to try and save it.

When should I reapply the spray? I guess I need to do this every year so when are the best times to apply in general?

I used a hose end sprayer but not all the wooly stuff came off. I read this is normal, that the spray only kills the bugs. Hopefully the water sprays will help knock out the rest.

There's another tree close to it that doesn't appear to be infested. It kinda looks like a hemlock but I'm not sure.

Can anyone tell me what kind of tree this is?

Follow-Up Postings:

RE: Hemlock Help - Wooly Adelgid

Bergen, I have some good info from a recent Rutgers U. workshop, but left it at work. Will post tomorrow.

You're going to have to be very timely and persistent with your applications - these are a stubborn pest and, as you probably know, can destroy your tree.

RE: Hemlock Help - Wooly Adelgid

thanks! I look forward to reading what you provide.

The tree is in pretty bad shape already. Went a couple years or more without being sprayed. I'd say maybe half the needles are gone if not more.

I have been seeing some new growth in a few spots. I hope that means chances are good that it will recover.

Any idea what kind of tree is in the picture?

RE: Hemlock Help - Wooly Adelgid

I searched through the Rutgers site and found this paper on The Hemlock Woolly Adelgid:
Life Cycle, Monitoring, and Pest Management in New Jersey

Looks like next august-september would be a good time to respray with a 1% horticultural oil. It should also be more effective then the spraying I did in june.

I'm going to keep spraying it once a week or so with plain water try and disloddge any insects that may still be on or recently landed on it and hope it comes back.

There's already some signs of new growth so I hope it can be saved.

RE: Hemlock Help - Wooly Adelgid

The mystery tree resembles my Tsuga caroliniana,(if that's how it's spelled), the carolina hemlock. The needles are not in two neat rows like the more common hemlock. For years my carolina hemlocks resisted the insect while it attacked the nearby more common hemlocks, but now they have been badly infested also.

RE: Hemlock Help - Wooly Adelgid

I'm glad you found the Rutgers paper; that should be an excellent resource. I trust you took note about not fertilizing the infested tree? There's little I can add, except the following excerpted from a lecture this spring given by Rich Buckley, Director of Soil Testing and Plant Diagnostic Services for Rutgers:

It would help if you can be sure you're dealing with hemlock woolly adelgid and not elongate hemlock scale. The two are easily confused. Both are protected by the white, waxy coating they exude, but the adelgid seems to settle at the base of the needles, whereas the adult scales are found on the needles. Rich did mention that he feels that imidacloprid (Merit) is more effective against the adelgid than the dormant oil, however it is not effective against the scale.

The lecture notes recommend "dormant insecticidal oils for light infestations of HWA, imidacloprid for heavy infestations in May." For the EHS, the recommendation "dormant oil treatments may suppress small populations; use an insecticidal oil or soap when crawlers appear in May and September."

We lost one of our beautiful 80-year-old Sargent's Weeping Hemlocks at the park to HWAdelgid ... amazing, isn't it, that such a tiny, short-lived thing can destroy something vastly larger and with such a longer life-expectancy.

Be consistent and persistent and you just may beat those little devils. Good luck!

RE: Hemlock Help - Wooly Adelgid

Thanks for all the info.

The pics of carolina hemlocks looks close but I'm still not 100% sure. Wish I knew more about trees. Regardless, I'm spraying that as well as the yews and another bush I have no idea what it is. From reading about the horticultural oil it may not help any but it shouldn't hurt. I'm worried that the spraying of the infested tree might make some of the HWA airborne and land on the other tree and it might be a hemlock.

One thing, the infested tree in bad shape also doesn't get a lot of sun, but the other tree a few feet away gets a lot more sun.

I don't fertilize he trees in genera and I'll be careful when I apply fertilizer to the lawn. I had to put some starter fertilizer a couple of years ago when I reseeded that area. Wonder if that was what triggered it to get worse.

The white spots are at the base of the needles so I'm pretty sure it's HWA. I didn't see any signs of scale on the needles. I think there might have been a layer of green film like moss or something on the trunk and branches before I sprayed. Not sure.

One odd thing. There was a clump of dead branches near the top that I tried to knock down. Got most of it. At first I thought it might have been a bird's nest but I didn't see any bird activity there for a long time.

When I knocked it down I saw some odd things. There was a long cottony yarn looking thing. A few feet long. There was also some almost netted type stuff that almost looked like deteriorating cassette tape but thinner and darker. Not sure what the black stuff was but was wondering if the yarn looking thing was related to the HWA. There was no active growth there.

There are quite a few dead branches in the tree. The only growth seems to be on the outside. The inside of the tree is mostly devoid of any needles.

Each day though I notice more and more new growth.

RE: Hemlock Help - Wooly Adelgid

FWIW, I have hemlocks that have been living with woolly adelgid for nine years. They are in a shady, sheltered spot so don't face drought stress, and they look decent. They don't matter enough for me to go on a strict spraying program, so I never bothered. I don't know how big the Japanese ladybug is that has been introduced to prey on the adelgid, but every now and then I do see a small round black beetle there, about 2 mm. long.

My neighbor hired a tree company for the sprays but eventually gave up and had them taken down.

RE: Hemlock Help - Wooly Adelgid - predator

Link to the ladybug. Looks like my little black guys. Don't know if they're commercially available.

RE: Hemlock Help - Wooly Adelgid

Predators of the HWA are being raised at the Phillip Alampi Beneficial Insect Rearing Lab, a division of the NJ Dept. of Agriculture, located outside of Trenton, NJ. Some insects are available for purchase by the public. Better call first to see if these available. It's best to go pick them up rather than have them shipped ... besides, it's a very interesting place. (Ummm, little plug here: They'll have a display at the Monmouth County Fair in the Home & Garden Tent July 23, 24, 25, and will have staff there with additional (and some live) display materials during the day on Sat & Sun, July 26 & 27.)

The following link will take you the NJDA page with info on the Lab, directions, phone number, etc. To get more information on the insects they're working with, click on "Biological Control of Plant Pests" on the right-hand menu - the HWA is right at the top.

The value of the tree is always a consideration in deciding how aggressive one wishes to be with a remedial strategy. In the case of our 80-year-old Sargent's Weeping Hemlocks at the park (I wish I had a good picture to post), there was no doubt that an aggressive approach was needed. In other cases, it may be best to let nature take its course, or just remove the infested tree and replace with something else.

Bergenjersey, the long, stringy stuff sounds like maybe there was a bird's nest up there ... or maybe some active young boys in the neighborhood? My sons were trying to see how high they could toss an old bicycle tire and it got stuck in the topmost limbs of an old dogwood ... hasn't fallen/blown down yet, can't reach it without a bucket truck, and someday somebody's going to move in here and wonder how the heck that got up there! (Thank goodness it's camouflaged by limbs from other trees.)

Remember that the waxy coating may persist long after the critter that made it is dead, so what you're seeing could just be remnants. You could try taking a sample in to your local extension office to see if they can advise on the status of your adelgids.

Here is a link that might be useful: NJDA Beneficial Insect Rearing Lab

RE: Hemlock Help - Wooly Adelgid

Great information thanks for sharing. I think you might find the following article from Arnoldia interesting. kt

Here is a link that might be useful: The Role of Arboreta in Studying the Evolution of Host Resistance to the Hemlock Woolly Adelgid

RE: Hemlock Help - Wooly Adelgid

I'm going to stick with the oil sprays for now and see how ti goes before investigating putting more bugs in the area.

I noticed that a lot of the white substance has washed off of the needles. Not all but a good portion.

There is one branch on an upper portion that is still very much covered. It was sprayed properly but because of the distance and position it couldn't get the pressure to wash off the substance. Most of the needles are brown/yellow.

It also sticks out a bit. I'm hesitant to prune the tree because it has already lost a lot of needles but do you think it would be ok to remove that eyesore from the tree?

RE: Hemlock Help - Wooly Adelgid

Someone else may have an answer for you, but I wouldn't dare try answer that question, especially without knowing how much of the tree you would be removing. If this tree is valuable to you, you may wish to at least get an estimate from a good certified tree expert; the consult and estimate should cover whether any pruning is advised, and how much, as well as any treatments they would recommend/provide.

Remember that while deciduous trees are "engineered" to lose and replace all their leaves every year, evergreens are not made this way. Some can withstand even a heavy pruning and bounce back with vigor, others cannot.

FYI, and somewhat tangential, below is a photo of one of our Sargent's Weeping Hemlocks at the park ... awesome trees.


RE: Hemlock Help - Wooly Adelgid

Thanks again for the advice. I was going to just cut off one branch because it was quite yellow/brown. Yesterday I noticed some new bright green growth on it and decided to leave it as is and see if it begins to thrive again. From looking at it now it looks half dead so I don't want to trim any growth now, especially not new growth. That one branch just bothered me because it really sticks out.

I tried removing some more of the dead branches that were probably a nest to increase the circulation of air, water and sunshine.

By the way what park is that exactly?

RE: Hemlock Help - Wooly Adelgid

I don't think it can hurt to give that branch some time and see how it does before doing any drastic pruning ... they're awfully hard to put back once they've been cut off ;-) I'm glad to hear there's some new growth appearing.

That view is down through the Rockery towards the Parterre (just planted with 180+ rose bushes) at Deep Cut Gardens in Middletown, part of the Monmouth County Park System. Out there beyond the tree line is Sandy Hook Bay. Those trees were planted around 1935-37 and are judged to be now about 80 years old. It's only about 5 minutes off the Garden State Parkway (Exit 114), so if you're in the area, like "down the shore" on a fine summer day, please do come visit ... admission's free!


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