مرض فيروسي مركب Virus Disease Complex
يصاب الذرة بفيروسين هما فيروس التقزم الأصفر MCDV وفيروس الموزيك المتقزم MDMV وكلاهما يسبب اصفرار وتقزم النباتات، كل الفيروسين يعدي الذرة منفردا ولكن من المعتاد ان يتواجد الفيروسين في نفس النبات، ينتقل المرض من حشيشة جونسون الي الذرة بواسطة حشرات المن وقفازات الأوراق (النطاطات)
Virus Disease Complex
Maize chlorotic dwarf virus (MCDV) and maize dwarf mosaic virus (MDMV) are often confused with other growth problems since they cause stunting, yellowing and reddening of foliage. These symptoms along with the presence of Johnson grass—alternate host for these viruses—are usually sufficient to diagnose the virus complex. While each virus disease may be found alone, they often infect the same plant and are difficult to distinguish. MCDV produces a deeper, reddish discoloration of upper leaves than does MDMV which is more likely to cause yellow color and a mosaic pattern of light and dark green color. MCDV is also characterized by more bunching or shortening of internodes. These viruses are transmitted from Johnson grass to corn by aphids (MDMV) and leafhoppers (MCDV).