Zucchini yellow mosaic virus

Zucchini yellow mosaic virus (ZYMV) is an aphid-borne potyvirus, regarded as a major pathogen of cucurbits in most regions of the world where these crops are cultivated. ZYMV affects all cucurbits including pumpkins, squashes, vegetable marrows, courgettes, melons, watermelons, cucumbers, gherkins and various gourds especially zucchinis. The effects are severe leaf mosaic, yellowing and eventually "shoestring" symptoms in the leaves. The fruits are stunted, twisted and deformed by raised protuberances, which reduces yield and makes them unmarketable in some cultures. In cultivated crops plants cease producing marketable fruits within 1 C2 weeks of infection and serious financial losses can occur, particularly in courgette and marrow crops.

from Wikipedia