Zaf said:

Ive got cucumbers in a grow bag in a greenhouse, last year in the same
position they were great, lots of fruit and no problems, this year they
are being treated exactly the same but after the fruit has developed to
about 1" long it turns yellow and wilts (or rots?).

The leaves look OK and there is no obvious sign of pests or diseases,
any ideas please?

I would suspect lack of pollination. This could be due to lack of
pollinators visiting the plants, or due to a lack of male flowers.

Some cucumber cultivars are gynoecious (bear only female flowers),
and require another cucumber cultivar to pollinate them. Usually seeds
for a pollinator variety are included in packets of gynoecious cultivars.
Home gardeners growing only a few cucumber plants risk not having
enough plants to ensure one of them is the pollinator cultivar.

Cucumbers cultivars can also be parthenocarpic (set fruit without
pollination) and these cultivars are ideal for greenhouse growing.


--
Pat in Plymouth MI

"Vegetables are like bombs packed tight with all kinds of important
nutrients..." --Largo Potter, Valkyria Chronicles

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