Effect of Combination between Bioagents and Solarization on Management of Crown-and Stem-Rot of Egyptian Clover

Abstract

Fourteen isolates of Trichoderma sp. and eight isolates of Bacillus sp., isolated from a field has severe infection by stem and crown-rot of Egyptian clover plants were screened for their efficacy against the fungus Sclerotinia sclerotiorum Lib. de Bary, the causal of crown and stem-rot of Egyptian clover, in vitro and in vivo. In general, Bacillus spp. were more efficient in reducing the radial growth of S.sclerotiorum than Trichoderma spp and the opposite was found in case of sclerotial germination. In addition, the isolates of B.thuringiensis and T.harzianum showed maximum percentages of radial growth inhibition and sclerotial viability. Meanwhile, isolates of B. pumilus and T.viride resulted in the lowest percentages of radial growth inhibition and sclerotial viability . The tested bioagents, i.e. B.thuringiensis-1 and T.harzianum-3 as well as soil solarization resulted in significant reduction to the severity of clover crown and stem-rot with significant increase to the green forage yield compared with control treatment. In addition, T.harzianum-3. was more efficient than B.thuringiensis-1 and solarization ,when each of them was applied alone. Moreover, the combination among B.thuringiensis-1 + T.harzianum-3 + solarization was the most efficient in this regard, which no apparent infection by crown and stem-rot was detected and the highest green forage yield was obtained. However, the combination between solarization and any of the tested bioagents was of intermediate effect in this regard.