The Gardener's Almanac

Your courgettes have been infected with mosaic virus disease.

 

The virus enters the plant through the sap, and is spread by greenfly when feeding.

 

I am afraid there is no control, it would be best to remove them before they affect adjacent plants.

White fly are becoming immune to a number of the insecticides available today.

 

To clear up an attack spray weekly with various white fly designated insecticides.

 

Each week use a different type, as this tends to weaken them and overcome the immunity.

 

Ensure you coat the underside of the leaves with the insecticide.