Downy mildew

The upper surfaces of leaves show slight yellowing while on the underside of the leaf a greyish fungal growth develops. Older leaves develop fine black speckling.

The disease tends to occur in plants raised under protection during late winter/spring or in the autumn. Spread is by airborne spores.

The disease is favoured by cool humid conditions. Avoid having plant foliage wet for long periods of time and keep propagating houses well ventilated.