Intensity of wheat infection by the fungus gaeumannomyces graminis

In 2002 and 2003, wheat fields on the territory of Una-Sana Canton (northwestern Bosnia) were regularly inspected. In addition to the common diseases (powdery mildew, leaf rust, septoria), occurrence of Gaeumannomyces graminis (Sacc.) von Arx et Olivier (syn. Ophiobolus graminis Sacc.) was registered in a large number of localities. Symptoms of the disease could be observed at the stage of milk maturity and beginning of wax maturity. The infected spikes were white, empty, with a small number of poorly filled grains. Microscopy observations of the roots showed In object reinstatement diagnosis was examined root and under microscope was espied fibrous stuff long some mm were established on exterior and interior mycelia. The consequent tissue necrosis and root rot created conditions favorable for the attack of parasites causing "black spikes". The fungus G. graminis was isolated from a large number of collected wheat samples which were analyzed in the laboratory by the conventional method. In 2002, infection symptoms were found at 35% of the wheat acreage, in 2003 at 32% of the acreage. Infection intensity above 15 was registered at 8-10% of the infected acreage. The computed severity coefficients of noxiousness ranged from 10 to 35. The lowest coefficient was established for the cultivar Bosanka, the highest for the cultivar Marija. After harvest, infected wheat grains were measured for absolute and hectoliter weights, which were found to range from 25 to 30 g and from 60 to 70 kg, respectively. To improve the effectiveness of crop protection, it is necessary to apply the required agricultural practices (long-term crop rotation, control of volunteer wheat and grassy weeds, plowing under of harvest residues, balanced fertilization) and treat wheat seed with fungicides from the groups of benzimidazoles, triazoles and triadimenoles.