Dudchenko V. Biological basis of plant protection system for blast control under the Steppe zone of Southern Ukraine conditions

The thesis deals with motivation of plant protection system for blast control with provision for biological particularities of incitant diseases. The fungus is well saved in autumn-winter period. The nodes and panicle of rice are most suitable substratum for conservation and renewal to infections in the following growing season. The optimum temperature for vegetative growing P. oryzae - 26-28 0С, for sporulation happens - from 22 up to 25 0С. The conidium formation on leaves of rice last at the average 21 days. Most amount an spores (5761-8168) fungus works out as from sixth on tenth day from begin sporification. The fungus caused blast desease is capable of form from 6 up to 10 generations for growing period of Ukraine conditions. The infection of plants by leaf blast before heading phase brings about losses 27-93% harvests, in case infection in flowering phase the harvest reduces on 12-68%. The neck blast can be a reason of loss from 10% up to 100% harvests. Some reduction of disease severity extension (on 14-25%) was observed after application phosphate and potassium (N180P90K60+30) on high N levels. Among the perspective varieties of rice those immune to blast were not detected. Such of varieties as Spaltchik, Dniprovsky, Antey, Yantarny, UkrNDC-6952, UkrNDC-6744, UkrNDC-7384 were less injured. Such of fungicides as Bavistin and Topsin M were most toxic for P. oryzae mycelium. Using them in amount 0,5-1,0 kg/ga allows to reduce the development diseases on 52,9-64,2%. Using an fungicides together with plant growth regulators raise their economic efficiency. Productivity herewith 71,1-73,6 centners per ha.