Q. I am inquiring about wasp galls on the underside of oak
leaves. I am in the commercial tree business. Any control measures that have been found to minimize the wasp from
laying the eggs or stop the oak from forming the fuzz ball? As I recall the
fuzz ball is reaction from the oak defending itself. Any information would be
greatly appreciated.
leaves. I am in the commercial tree business. Any control measures that have been found to minimize the wasp from
laying the eggs or stop the oak from forming the fuzz ball? As I recall the
fuzz ball is reaction from the oak defending itself. Any information would be
greatly appreciated.
 |
| Oak leaf gall |
A. Plant leaf galls can be caused by fungi, bacteria and
insects like aphids, moths, midges, wasps as well as mites. You can identify
what caused the gall by its shape and color and the host plant. In this particular
case, if we are seeing the same picture in our minds, you are right, it is
caused by egg laying of a tiny wasp.
insects like aphids, moths, midges, wasps as well as mites. You can identify
what caused the gall by its shape and color and the host plant. In this particular
case, if we are seeing the same picture in our minds, you are right, it is
caused by egg laying of a tiny wasp.
 |
| Poplar flower gall caused by tiny mites |
Many times it is only a specific
insect or fungus that inhabits a specific species of oak or plant. If you had a
picture we could take it further. I remember seeing some leaf galls on native
oaks in the spring mountain range here. I assume they were caused by wasps as
well.
Galls produced on plants are unique
to the organism that caused it. Sometimes it is caused by feeding damage,
infection or reproduction. The pairing of an insect or fungus with a specific
species or type of oak in this instance is frequently unique.
to the organism that caused it. Sometimes it is caused by feeding damage,
infection or reproduction. The pairing of an insect or fungus with a specific
species or type of oak in this instance is frequently unique.
 |
| oak gall causing leaf drop |
A guy who is done a lot of work in
this area and in our part of the world is Ron Russo, a naturalist. Here is a
page taken from Natural History Magazine published in 2009.
I have been telling people to
appreciate nature and live with it. Unless it’s really causing problems like
defoliation I would leave it alone. I guess if I had to treat it I would
probably use something like imidacloprid as a soil drench when new leaves are
beginning to form.
appreciate nature and live with it. Unless it’s really causing problems like
defoliation I would leave it alone. I guess if I had to treat it I would
probably use something like imidacloprid as a soil drench when new leaves are
beginning to form.
The problem in treating for this
insect is that we don’t know it’s lifecycle. So we don’t know when it is laying
its eggs to put down a protective spray. I feel that a soil drench will give
the plant longer protection and is less of a problem to the environment.
insect is that we don’t know it’s lifecycle. So we don’t know when it is laying
its eggs to put down a protective spray. I feel that a soil drench will give
the plant longer protection and is less of a problem to the environment.
But I would really resist using
this insecticide unless I was forced to use it by the client. Environmental
concerns surrounding this product, in my opinion, don’t justify its use unless
it’s under extreme conditions.
this insecticide unless I was forced to use it by the client. Environmental
concerns surrounding this product, in my opinion, don’t justify its use unless
it’s under extreme conditions.
And even if you do use an
insecticide like this the old leaves will still have the galls and it will only
protect new growth.
insecticide like this the old leaves will still have the galls and it will only
protect new growth.
I will post your question and my response on my blog next
week and you can direct anyone with questions to that spot.
week and you can direct anyone with questions to that spot.