My experiences with aphids is that they vary with the degree of stress,
particularly nutritional, on plants, thus more with soil imbalance and more
in pots than in open, natural, balanced conditions.
In a greeenhouse 'permanent bed' you may have some substantial imbalance,
perhaps a potassium deficiency if you have been heavily cropping and heavily
watering. A small amount of pot ash, or mulching with straw, hay, maybe
chopped lucerne hay, may provide eventual help. Are you topping up with good
compost? Is there a rotation? Does the soil attract earthworm?
Are there any predators in the greenhouse? Are ladybirds, etc happy there.
Baby plants running on seed energy may do well until they start to shoot up
using the resources of a tired soil.
my thoughts; contradiction, improvement welcome
Dennis
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