It is possible that the cause might be Cherry aphid. These aphids attack the soft, young growth from spring to autumn causing leaves to yellow and curl. The small black aphids are normally found on the underside of leaves and could easily be mistaken for eggs. If the trees are also being well watered and fed with miracle grow then this is likely to produce lots of soft growth which is particularly attractive to aphids. They overwinter as shiny black eggs on the stem and branches.
We would suggest using an insecticide such as Bayer Provado Ultimate Bug Killer Ready to Use to reduce the population. Then in winter use an oil winter wash such as Growing Success Winter Tree Wash to remove overwintering eggs. This winter treatment is likely to be most effective at reducing the problem but you will need to be vigilant in spring for a recurrence of the problem in spring which may need respraying.
With regard to the lack of fruit, this may be due to the fact that they are still young trees or could be a pollination issue if the flowers are not being fertilised. What are the varieties of fruit trees that are being grown? Do they produce much flower?
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