Artificial windbreaks and the distribution of turnip mild yellows virus and Scaptomyza apicalis (Diptera) in a turnip crop

SUMMARY In a turnip crop natural infection with turnip mild yellows virus was greatest in two narrow zones, one to leeward of an artificial windbreak, the other in a long shallow depression in the earth. Both zones were approximately across wind when Myzus persicae flew in early summer. Later in the summer, similar windbreaks facing different prevailing winds increased the number of larvae of Scaptomyza apicalis on the plants immediately to leeward and windward of the windbreaks, probably because shelter affected adults that were flying and laying eggs in the crop.