What are these red bumps on my apple tree leaves?
Probably blister mites. I get them on some of my pears and ignore it every year. In my experience it has not been a big problem.
Is it going to spread? I have 2 other apple trees nearby.
It’s caused by bugs that recreate, so it could spread since bugs procreate many times a year.
It seems that blister mites have their favorite trees that they like to recreate in. My Yoinashi Asian pear draws in the blister mites, but the Korean Giant adjacent to it is rarely impacted/infested.
And do you see damage to your infested tree / fruit?
No impact on the fruit. As the season progresses the impact tends to be less.
Folks usually spray horticultural oil as dormant spray in fall and spring which can suppress mites. You can do this in Fall 2023 and Spring 2024 to to correct this problem next year.
You can find it on Amazon – “Monterey LG 6299 Horticultural Oil Concentrate”
Thanks! I missed my window this spring but will definitely hit it this fall.
Maybe the fall spray would work better than the delayed-dormant (spring) spray that I usually do. I missed my spring spray with horticultural oil and it seems no worse than usual.
I only did a spring spray last 2 years and seems fine too.
Also depends on the bug pressure.