I have a client with a Shumard oak who told me each year teh leaves turn brown and die before changing color (this was after the leaves were long gone for the year). A little Internet research turned up scorch as a possible cause and I sent her the info. She called back saying the symptoms matched.

When she had a replacement planted, she asked the nursery about the problem. They suggested adding zinc sulfate to teh root zone when the tree starts to leaf out. Their idea apparently was to improve tree health so it can fight off the bacteria.

Is this a reasonable treatment? With no other Shumards nearby, I don't see a big risk in leaving the tree for now, but the info I found suggests there is no cure and the only treatment is repeated antibiotic injections (not advisable as this is a very young tree still).

So, is teh nursery trying to sell some chemicals, or is there anything to this treatment. Also, I welcome any other ideas about saving this tree.

thanks,

keith

Reply to post by Keith, on February 16, 2002 at 10:14:52:

You are correct- there is no effective 'cure' at this time. Zinc or other single treatments will have little, if any effect. The bacteria (Xylella fastidiosa) is transmitted by various planthoppers and leafhoppers, among other possible vectors.

Keeping the tree healthy may reduce the chance of infection. However, the planthoppers will feed and breed on healthy trees, so I infection remains possible. Fertilization in this case shoudl follow standard protocol. Soil tests first (including a full micronutrient assay), then follow the recommendations.

It sounds like the infected tree was removed, correct? If so, there is no indication that the infection is transferred by root grafting, and will not transfer from old dead roots into the new tree. Infection of the new tree will have to occur by insect vector, and the risk is not all that great. Check with local sources to see how prevalent the bacterial scorch is there.

If the old infected tree is still present, you can have the tissue tested for bacterial scorch. Contact
Agdia, Inc.
30380 County Road 6
Elkhart, IN 46514
800-622-4342

They can advise you on tissue sampling and testing procedures, and can perform the tests.

Reply to post by Russ Carlson, on February 16, 2002 at 10:14:52:

Russ,

thanks for the ideas. Actually, the tree is still standing, which is why the nursery wants to apply the chemical. As a climber first and diagnostician second, it never occurred to me to get the tissue tested. I'll look into that and suggest it to the client.

k