EFFECT OF SUBSTRATE AND DOSE RATE ON THE EFFICACY OF TRICHODERMA HARZIANUM RIFA1 AGAINST RHIZOCTONIA SOLANI KüHN IN POTATO

摘要

A pot experiment in a screen house at the Agriculture Research Farm of NWFP Agricultural University, Peshawar was conducted during 2002-03 to find out the effect of substrate and dose rate on the biocontrol efficacy of Trichoderma harzianum against Rhizoctonia solani, the causal organism of black scurf disease in potato. The antagonist was applied on wheat bran or rice husk, each at 10. 20 or 40 g/pot. In general, all the treatments with T. harzianum were effective in reducing the disease when compared with the inoculated and unprotected controls. Plants treated with T. harzianum on wheat bran at 40 g/pot showed the lowest severity (10 75%) of the disease and maximum yield (85.58 g/pot). Fresh root weight, shoot weight, plant height, number of stemsper plant and number and weight of medium size tubers were also significantly (P<0.05) higher in this than the other treatments. A significant increase in total tuber yield was recorded with increasing the dose rate of both wheat bran and rice husk. This trend was more pronounced in the presence of T. harzianum than in its absence. Such a dose effect was, however, not observed in decreasing disease severity particularly in the absence of T. harzianum. The important factor determining reduction in disease severity was the presence of T. harzianum regardless of substrate dose.