bug or disease?

[ptjeff]

Has anybody seen things like this? this is a silver maple that i have had for a few years and last year it developed these bumps and knots. the leaf does not curl up into a ball nor turn any abnormal color. it just gets these bumps. have not seen any mites, scales, maybe a spider. have sprayed with Seven, thinking of Malathion.

 

[edprocoat]

I have seen that before, I can not tell you what causes it, but its prevelant here in central Ohio. I see it on trees in lawns all the time. It does not seem to hurt the trees, some get it on a few leaves while others get it almost every leaf. It seems to be only on maples too, I bet it some kind of fungus that gets in the leave.

ed

 

[treebeard55]

Those look like galls. A gall is a plant's response to some irritant -- an insect, whatever -- and the function is to wall the irritant off. (Like a pearl is an oyster's way of walling off an irritating grain of sand.) Some insects are known to provoke gall formation to have a nice place to hide!

Galls can be formed on leaves, wood, or (I presume) roots. Leaf galls are common on maples. They don't harm the plant, except in unusual cases. They are unsightly, yes. I know of no way to prevent them except to deal with the irritant that provokes the response in the first place.

 

[ptjeff]

treebeard55,
last year they were pretty prevelant so i defoliated these trees and the next bunch of leaves came out smaller, just like it should, then the galls formed again. I did look at the big leaves and cut apart the gall under the extreme magnification, expecting to see some sort of critter, but it was an empty vault with the opening on the underside of the leaf. I really am suspecting a spider because there have been intermittant webs spun overnight for the last few years.

edprocoat,
where in central Ohio are you? I live in "the mistake by the lake"
do you know of any local Bonsai club functions?

 

[garywood]

Di-SYSTON a systemic granual
Wood

 

[Dav4]

I doubt spiders are your problem...their presence is sign that there are other tasty bugs around. Your best course of action might be to take an affected leaf to your county agriculture extension office and have an agent examine it.

 

[Mac In Oak Ridge]

I would get a fungicide called Mancozeb. Spray the tree about every two weeks from the time the buds look to be opening until the leaves drop in the fall. If you defoliate this year, spray after defoliation and when new buds form, then every two weeks.

 

[Kitsune]

I doubt spiders are your problem...their presence is sign that there are other tasty bugs around. Your best course of action might be to take an affected leaf to your county agriculture extension office and have an agent examine it.

^This this this. The galls can be caused by insects, but also fungus, bacteria and even certain plant viruses, and a local extension office (If you have a University with an agriculture program, they are also a good reference) can very likely tell you the cause of the galls. Without knowing, using any treatment is just like a shot in the dark. And, unfortunately, if it's a virus or bacterial cause, they are very difficult, sometimes impossible to treat. They may not be detrimental to the tree's health, but they are unsightly. To be honest, when you said you defoliated and these came back, it suggests strongly a systemic cause, like bacteria or virus, instead of an insect. Some fungus can also become systemic, so they can't be completely ruled out. Definately have an expert take a look, because there is likely a more common cause in your area.

Here on Long Island, there is a bacteria that is very common in our silver maples that cause similar galls, and which is largely untreatable.

 

[treebeard55]

Good points, Heather. I was going to say that sometimes the irritant that provokes a gall is microscopic, but you covered the topic quite well.

Every state has an Extension program, and agents are found in most larger towns -- at least here in IN. Peteyjeff, look in your phone book, under County Govt: good chance you'll find something. There may eve be a Master Gardener available to come to your house.

I'm sure the spider webs you've seen have nothing to do with the formation of the galls.