plant diseases caused by fungi of the genus Helminthosporium. Helminthosporioses usually infect grains and, in humid regions, certain industrial crops. The diseases are manifested by spottiness of leaves and fruit, darkening of embryos, and rot of roots and stalks. The pathogen is a parasite on plants in its conidial state, which develops mycelia inside plant tissues. Helminthosporioses are spread in plant seeds and remains. Among the most harmful is barley stripe (pathogen, H. gramineum), which is one of the worst diseases for this crop. The leaves are covered with elongated spots, which often extend from the tip to the base and are bordered by dark rings. The leaves shred, turn brown, and dry up, and the seeds blacken at the embryo. Net blotch (pathogen, H. teres) is characterized by the appearance of brown, oval spots with pale yellow rings on the leaves of the barley plant. These contain both longitudinal and transverse dark brown bands. Affected seeds have a brown border around the embryos.
Helminthosporiosis of oats (pathogen, H. avenae) causes elongated, narrow spots with reddish brown borders on the leaves, and the seeds darken at the embryo. In corn (pathogen, H. turcicum) elongated, dark spots appear on the leaves and may be as large as 10-20 cm. The tissue inside the spots dries and whitens, and a reddish brown border remains around the spot. This variety of helminthosporiosis also attacks sorghum and Sudan grass. In rice (pathogen, H. oryzae) the sprouts at the root neck are covered by a leaden gray velvety deposit, and the leaves develop small dark brown spots. Plantings are severely thinned by the disease. Helminthosporiosis of poppies (pathogen, H. papaveris) is one of the most destructive poppy diseases. The entire plant is covered with brown spots, and infected seeds are dark brown. Helminthosporioses can be controlled by agricultural techniques that hasten the mineralization of stubble, by collection and destruction of plant remains, and by cleaning, sorting, and fungicide treatment of seeds.
I. S. UZUNOV