If I find a small amount of wooly apple aphids on a MM111 tree, can I assume that roots are ok? I thought the rootstock was resistant and I’m treating with foliar spray. I’d rather not go systemic.
I got them on wood last year (mostly on wounds and pruning cuts) and I used raw neem oil (not diluted), applied with a brush and wooly apple aphids were gone.
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Good idea!
I assume if you see only a little above ground then there’s only a little below ground. As I read, part of the life cycle of this aphid is below ground, and part of its life cycle is above ground. So if you only see a little above ground (and you get rid of it fast), I would surmise your roots are okay because the observed population is small.
I also noted a few wooly apple aphids on my trees here and there, and I digitally exterminate them immediately.
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where they on the rootstock? (bur knots or suckers)
Or on the scion above ground part of the tree?
The MM111 resistance is only for the rootstock. It does not transfer to the grafted scion.
I assume the WAA are on the scion. They probably came from overwintering WAA from another tree (with a non resistant rootstock)
Or overwintered on the scion part of the tree.
You might wonder why we use resistant rootstocks if it does not transfer to the scion?
That’s because of the lifecycle. The WAA tends to overwinter on the roots below ground. With resistant rootstocks this is harder. And thus you tend to “brake” it’s lifecycle. And avoid a recurring exponential growing population.
It however does not mean you’ll never see a WAA on a tree with a resistant rootstock. Just that it’s much less likely to become a problem.
like always resistant = not immune
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I get wooly aphids every year on just one of my apple trees- it’s a “garden delicious” genetic dwarf on seedling rootstock. But I’ve found that they are very easy to kill if you catch them before they spread too much. Neem works fine, but insecticidal soap works just as well. As long as you get a direct hit on each cluster and drench them with soap. Neem is fairly safe but I like using insecticidal soap because it’s about as harmless as hand soap (and smells kinda nice while you’re spraying it).
On the tree not the rootstock. I thought the resistance would confer.
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the resistance doesn’t confer to the scion. So there is nothing to worry about. It’s working as intended.
Probably doesn’t hurt to treat the WAA. No need for systematics.
If you got non resistant rootstocks around. Probably good idea to control them.
If you only got resistant rootstocks you could depending on disease pressure etc wait and see.
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