Pests and Diseases

Blight

Blight occurs in mild, moist conditions.
The initial signs are the development of small dark areas on the leaves. White threads appear on the underside. The stems may also develop dark brown patches at areas where leaves join them. Infected tubers have brownish discolouration and the flesh has a marbled appearance before rotting away.

PCN (Potato Cyst Nematodes)

Plants will appear stunted and weak with the foliage having a dull wilting appearance.  Cysts of approx. 0.05mm in diameter will appear on the roots and tubers.  There are two species of PCN which occur during mid-July and mid-August.  The species are best deciphered by their colour, Golden Yellow cysts = Globodera rostochiensis, Creamy White cysts = Globodera pallida.  These cysts in both strains will turn a reddish brown colour at maturity.

Blackleg

This is a common bacterial soft rot.  When this occurs the stem of the potato is infected, it will turn black and decompose, followed quickly by the potatoes. The plant leaves turn yellow and the plant slumps.

Common Scab

Common Scab is caused by a fungus.  Cases are worst in dry conditions, however watering at the time tubers are developing will decrease the level of infection in tubers.  Levels are also lower in slightly acid soils.  Scab is superficial – it does not affect yield but it is unattractive.

Slugs

A common problem in potatoes.  Showing as odd shaped holes on the surface leading into large holes in the actual tuber.  More common in potatoes planted in heavy wet soil.  A late harvest may mean tubers are more at risk as slugs are more active around the late autumn period.

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