Need help with scale infested Hemlock.

Reply to post by MBurke, on June 20, 1999 at 21:31:57:

What help do you need? Where are you located?

Have you identified the pest? THere are several species of scale that infest hemlocks. Horitcultural oil either dormant or summer can provide control. Insecticidal soap is also recommended when crawlers are active. The key to control is several repeated treatments and thorough coverage.

Be sure to follow instructions and local and state regulation regarding pesticide handling and use.

Reply to post by Russ Carlson, on June 20, 1999 at 21:31:57:


I was interested in the control of scale insects on Tsuga{they seem to resemble soft scales} through beneficial predators, I am not positive if the species, Is there a lab in the mid-atlantic region which can identify and or provide/suggest control measures. Literature which is detailed with photos and various information on life cycles etc. would be helpfull.

Reply to post by MBurke, on June 22, 1999 at 08:07:05:

Do you have access to 'Insects that Feed on Trees and Shrubs, by Johnson and Lyon?
Hemlock woolly adelges, p 78
Hemlock scale p 102
Elongate hemlock scale p 104

Check with your local Cooperative Extension office for identification and documentation. They will also be able to recommend treatments.

Reply to post by Russ Carlson, on June 22, 1999 at 16:00:22:

Russ in SE NY and SW CT we've also had infestations of Hemlock Fiorinia Scale which were much more intensive and damaging than HS. Don't have J&S handy, but the scale is more eliptical or elongated than the round, HS.

Infested trees will develop an overall grayish color and produce little new growth.

As I recall you're dead on about treatment. Dormant plus two additional treatments (mid-June and mid-Sept. with the labled materiall 15 years ago.) The key is thorough coverage which is why I believe the multiple treatments are so important.... what you miss on one application might be covered on another. With contact materials it's also crucial to get the underside of the needles. Systemics (if labled) ease the coverage and underside issues somewhat.

No experience with natural predators, but I suspect they are out there. I see fewer infested looking trees than I used to as I drive around, but now we have the adelgid on many trees. The off-color appearance is somewhat similar but HWA victims look thinner than I recall HFS victims looking and of course the snowy little critters are visible.

As with all, good cultural conditions pre-dispose trees to resist infestation and help overcome it. Hemlocks seem hard to turn around, however, once damaged.

Reply to post by Scott Cullen, on June 23, 1999 at 22:08:48:

Fiorinia is the Elongate Hemlock scale. Usually more populus than the Hemlock scale.

Coverage and timing are extremely important in controlling any of these. When you throw in spider and rust mites, hemlocks aren't worth keeping anymore.

Reply to post by Russ Carlson, on July 04, 1999 at 06:07:37:

It's funny, when I was growing up one of the first pests I learned to identify was spider mites on the hemlocks. When HFS was around in the early 70's it was really around but I saw fewer mite problems and the HS seemed less common too. Now that adelgid is rampant I seem to see less HFS. Maybe one just focuses on the current problem amnd pays less attention to the rest.

In any event, yes, hemlocks are a somewhat risky landscape investment these days if you are talking about large, mature material. Here in SW CT & SE NY you can see both individuals and stands declining, mostly from adelgid I think. As you point out the problem is getting thorough coverage on large trees with spray materials either economically or at all.

Reply to post by Scott, on July 05, 1999 at 21:53:47:

I think there is some indication that Merit insecticide gives control of HWA with soil injection. Would like to hear any comments on this by those who have tried it. Does it seem to help? Do repeated treatments improve control?

Reply to post by Russ Carlson, on July 06, 1999 at 05:46:15:

I was wondering if there might be some method such as fertilizing or pruning to encourage a older and ragedy Hemlock to produce healthy new foilage, as seen in younger specimens, I would suspect there would be little remedy for a older tree. Like older arborvitae which have little inner foilage,
I think I already know the answer but...