I live right next to a park with some mature maples..yesterday I spotted these red things on the leaves of a tree in the park about 50yards from my fence. Any ideas, I am concerned they could infiltrate my garden. They are static and don't appear to be aphids, they seem to be rooted into the leaf...i think they must be a parasite of some kind but i have no idea. What are these and do they pose a threat to my JMs
@dicky5ash , IMO they look like Gall mites. They do chomp through leaves in great numbers. There is no way to stop them coming your way. But be observant to your trees and spray with an insecticide at first site. If you google gall mites you will see how similar they are to yours. I have very large London plain trees closeby that gets covered in them in the Spring, but to date they have never ventured to my maples. If the trees near you are large then the mites will have enough food to keep them happy. Hope that's of help.
A good macro photo of the mite or insect would help a lot for its identification. They look very large to be mites and mites usually appear when it is very hot and the air is very dry. It may be some type of aphid which develops more when it is cold. See if ants go up and down the maples, if so, they are aphids
So, good info, these are indeed gall mites. Just want to clear up a couple of issues. What happens is the mite reproduces in the leaf, which causes the red vegetal reaction to the irritation. You can't actually see the mite, it's protected inside. For this reason, contact insecticide is ineffective, and IIRC I've read that even systemic will not effect the breeding cycle. They pose no threat beyond disfiguring leaves. The only treatment I know of is to cut and burn affected leaves. However our contributor @opusoculi has mentioned that a winter application of sulfur can destroy them. I don't know that this works, but I have got rid of them on some variegated sycamores by cutting off the invaded leaves and composting them. HTH!
Yes: galls are not a problem, they don't put the life of a tree at risk. There are some spectacular ones on oaks, the size of a hazel nut or on lime trees, that look like small chilli peppers.
I agree with Alain, no danger for maple trees. No insecticid, even systemic, affects mites because mites are not insects; this the main reason emery. Sulfur prevents the development of mites . There are différent case. -Plant mites die in the fall but lay eggs growing the following year; for example, on young vine leaves, red blowouts are very visible when buds burst; the common name is perinosis (érinose in french), for it, sulfur is effective in april for wine yard if the weather is dry with sun. -Mites develop very quickly in greenhouse,(terrible weaver spider mite = tétranique tisserand in french) the sulfur treatment is effective at the end of summer; before laying of course. -Pear trees are attacked by a variety of mites that are very difficult to remove, because they cause the leaves to curle. In this case, sulfur is used from october to march and april. -To destroy egg laying, a spray of water-soluble oil is also effective at the end of winter. But for maples nothing is necessary. And (edit) for pear scab, the use of liquid sulfur is as effective as products with systemic effects. Always very interested reading your forum.
