How to save Hemlocks from Wooly Adelgid

[chainsaw_louie]

Hi,

I recently discovered that the big hemlocks I have next to the house have scale and wooly adelgid.   I've paid a fella $300 to come and spray horticultural oil on it - once in may and once in june. He is to come and hit them again in the fall.

Its been real dry here in NY so Ive recently been watering the ground below the trees hoping to relieve the drought stress. 

Any suggestions on how to save these trees?

Thanks.

Tim

[SwampDonkey]

Wish I could help you out here. A friend of mine was working with the forest service through Virginia Tech in identifying sites for control. He now has taken a different position in Pennylvania. Haven't heard from him since this spring. Possiblly the forest service has information on their regional sites. Up here we get it (or something similar) in balsam fir and is most damaging in Christmas tree farms. We have hemlock also, but it's not considered a high value tree in my region. That being said, I like hemlock and would like to establish some on my woodlot. Sap sucker is a real problem here, they pepper the tree trunk with bore holes.  >:(

[nyforester]

Hello Chainsaw
One key factor here is health. If the tree is healthy it should be able to fend off most intrusion.
Go to your local plant store (even Walmart) and get yourself some fertilizer sticks. They come 8 or 10 to a pack. Buy the generic brand. They have the same ingredients as the well known brands, however they are much less money. I use several (maybe 8-10) on large trees in my yard. They are slow release so it will not shock them. You want to drive them into the soil just inside the outside drip edge of the crown. This is where the feeder roots are located. I use a large screw driver and make a pilot hole in the soil. Then I pound them in with a hammer flush with the ground. You will not see results immidiatly, but do it at least twice a year. The tree will develope better color and more branching. This is a much cheaper $ avenue to take than chemicals. If all else fails........use the "chainsaw".
Pete

[SkidrowJoe]

Wooly Adelgids are peircing/suckering phloem feeding apihids that cover themselves with their own secretions, the white cottony stuff.  Treatment can be made with a horticulture oil usually in winter, starting in October and in to late winter.  Usually you can control the second generation of HWA in winter since they are young immatures.  Remember that Hort Oil is not good for application in the growing season for two reasons, the trees foilage can get scalded from the oil and the effect of the oil on mature HWA is minimal since they reached a mature stage and are covered in the white cottony secretion.  Fertilizing at this time may be problematic for the tree, since it is stressed the excess amounts of salts, etc in the fert may further the decline of the tree.  Address one problem at a time, once the tree is rid of the HWA then you can worry about annual fertilizing.  Remember trees like fert. with high nitrogen compounds a fert of 27-9-9 is about par for a tree.  I am not sure what these fert sticks are but the best application is usually deep root fert. with a high pressure spray rig.

Caution HWA can possibly kill a tree in one year if no measures of control are taken.

Hope this helps,
Steve

[Brian_Rhoad]

I was told that fertilizer seems to make the aphids eat the needles faster. I don't know if it is true or not.

[chainsaw_louie]

Thanks for the good information.  The fertilizer sticks seem like a good idea for my other trees as well.  I had read somewhere that the hemlock likes lots of water and prefers areas where the soil is moist.  The dry summer this year didnt help and I have been trying to water the trees under the drip line whenever possible.  I even had an idea of rerouting the kitchen sink drain pipe to pour out by the base of these trees - it would keep it moist but it wouldn't be code.

Tim

[bugboy]

hi,

i am the guy swampdonkey said was working on the problem.  hwa is an exotic insect and there are very few natural enemies that eat it.  Also, hemlock is HIGHLY susceptible to this insect.  The only real option we have is chemicals.  Research are bringing in bugs that eat it, but they are years away before any real impact is seen.

Hort oil works by smothering the hwa.  however, populations rebound very quickly. 

The best thing to do is get somebody to either treat the soil or inject the tree directly with imidacloprid.  there are a number of companies that specialize in this sort of treatment.  the most popular chemical is Merit.  this chemical is taken up inside the tree and the adelgid dies by eating it.  this chemical can also keep hwa off the tree for 3-5 years if done properly.  PLUS, it won't cost $300.  My guess is about 150 for 3-5 years worth of control.

once control is demonstrated, then fertilization is recommended.  don't do this before as the hwa likes nitrogen ;)

cheers,

[ToadHill]

In addition to Merit, if you find a local arborist who uses Tree Tech products they have an injectable product named Harpoon that I have had great success using on HWA.  The injection should be done in May for crawlers and again in August if further control is needed. In my experience it is less costly than Merit. 

[bugboy]

Imidacloprid (Merit) will likely become cheaper as it comes off patent.

If you need to treat twice, is the cost still less than treating once with merit?

[bugboy]

Harpoon is an organophosphate class of insecticide and is a 50% concentrate.   :-[

This might not be available in many areas.  Use this product with extreme care!!!

[ToadHill]

bugboy:  I've never had to treat a second time with Harpoon, however the Literature on the product offers it as an option.  I agree this product is an organophospate but in New York Merit is also a restricted use chemical.  Vivid ll (ABAMECTIN)  is also labeled for adelgids and is not a restricted use chemical.   

[bugboy]

I've used both Abamectin and Pointer (5% solution of imidacloprid) for stem injections with a new injection system.

I got control of hwa inside of a month with Pointer, but still waiting on the abamectin to kick in (i know it will, but it takes a little longer). 

Personally, i think most chemicals should be restricted use and things that happened in Long Island could be avoided in the future (hopefully).  by the way, Merit is not restricted use because of its toxicity or its persistence in the environment; it was because it was used improperly initially.  This is something that could have been avoided if only certified pesticide applicators were allowed to use it.  Harpoon IS restricted use because of its toxicity and persistence, i think.

Orthene is another good product for stem injections.  Moves well once injected.

I've used many chemicals in systemic injections for HWA that should have worked.   HOwever, the formulation was such that the ai did not move well inside the tree.  :(

Part of my job is to test new formulations of old ai's and new ai's for companies...

[KGNC]

Hello;
I'm new here and i don't want to highjack a thread my first day but I've got the same problem on a bigger scale. I have 25 acres with about 150 hemlocks of various sizes. The largest are 36" bhd. This last summer I saw the first indication of HWA. I had a local guy come out and quoted injecting each tree and spraying with oil as need for three years.  The total was $35k! That's not going to happen.
So, do I have any realistic options? I thought about buying a sprayer and trying to spray them twice a year but don't think I could reach the tops of a lot of them. All of the trees seem to be in good health right now and I hate the thought of a valley full of dead hemlocks. Any sugestions? I hate to start logging hemlock but I may have to.

[bugboy]

150 trees is a lot to treat.  If the trees are really large, treating with a foliar spray won't be effective. so, Yes, 35K is a lot.  If the trees are not near water, you can do a soil injection with Merit.  The cost would be about 6000, but only one treatment would be needed and it should last 3 to 4 years.

Alternatively, treat only your best trees and deal with the others either with an ax or let them go hoping to treat them later.

You might be able to convince somebody to release natural enemies into your area.  Ecoscientific solutions in NJ is growing beetles that eat HWA.  There's no guarantee the beetles will work, however, there is a guarantee the chemical will.

[KGNC]

Thanks for the info bugboy.
Most of the tree are within 50 ft of a stream that bisects the property so I don't think the soil injection could be used. If I were to get the stem injection treatment for the larger trees could I manage the Adelgids on the smaller trees with the foliar spray? thanks

[bugboy]

Stem injection is the best way to go.  I would not use an organophosphate near a stream no matter how legal it was.

I don't think you can even cover spray due to the proximity to the stream.  The trees won't die overnight.  why don't you treat a few this year, some next, etc.  Only treat the trees that have the highest HWA populations.  this way you'd kill the bulk of the population and perhaps delay infestation on other trees.

There are many stem injections you can use.  they range from good to great, slow to fast.  find out what options you have and then contact me again if you'd like for my opinion.

cheers,