Wednesday, July 28, 2010

Plant pathology:Lettuce necrotic yellows

Lettuce with the viral disease 'Lettuce Necrotic Yellows'
My Italian neighbour at the community garden lets the weed, milk or sow thistle (Sonchus oleraceus) establish itself in a small patch. It is a common and cosmopolitan weed found in many parts of the world. In Italy it is valued as a vegetable to cook with Spaghetti. However, the thistle aphid Hyperomyzus lactucae is the vector for a viral disease which causes lettuce to become stunted with lopsided growth and with many yellow leaves.The aphid is common in autumn around the time this lettuce seedling was planted.

Milk or Sow thistle: Sonchus oleraceus

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