I make no claim to be an expert on apple growing or anything else, but it surprises me how often I'm asked about ants. Not just in the context of apple growing, but with peaches, nectarines, and even in the vegetable garden.
A typical question is "my plant (apple tree, broad beans, runner beans, plum tree) is covered in ants - will they do any harm?"
The answer is "no", but the fact that ants are there should set the alarm bells ringing. The ants themselves are harmless, but the reason they are on your plant is that they are looking for aphids. If ants are there, you can be sure that your tree, or whatever it is, is being infested by aphids, and if you look carefully you will find them. Ants are attracted by aphids because of the honeydew which they secrete.
Ants therefore give an early warning of aphid attack. If it's at an early stage, you may see just one or two curly leaves where aphids have started their work, and these can be rubbed off with finger and thumb. But it's likely that a search will reveal more than this, so an early dousing of the new shoots (for this is where the aphids go) with insecticide is indicated. There's no need to spray the whole plant - just deal with the affected leaves.
On apple trees, there are three main aphid targets:
WOOLLY APHIS goes for damaged bark and leaf shoots just beneath the new leaves. Brush them off and then spray. Looks for small tufts of "cotton wool" which the aphids use to protect themselves.
Various green, brown and black aphids go for fresh leaves at the ends of new growth. Curly or yellowed leaves are the indication.
There are also new leaves and shoots within the clusters of new apples in May-June, and it's easy to miss them - they are not obvious. This is often the most frequent aphid target. Any curled or yellow leaves- rub thoroughly, pull off if necessary, and spray.
It's also worth keeping an eye open for aphids on broad beans (remove the tops and then spray), and plum aphid (infestations take over very quickly).
Nigel Deacon , Diversity website
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