Abstract: Bacillus spp. have been widely used in biological control of plant soil-borne diseases. Bacillus subtilis NCD-2 and Bacillus amyloliquefaciens Ba-2 were used as active ingredient to develop seed-treating agent (SA) against potato verticillium wilt. Through the screening of carriers, wetting agents and dispersants, the formulation of SA were defined as follows:talc powder 75%, NCD-2 raw powder 13.33%, Ba-2 raw powder 6.67%, dispersant B 3.50%, and wetting agents B 1.50%. It was determined that the appearance of the prepared seed treatment agent was light yellow powder with no agglomeration. The particle size of SA was 36.78 μm, pH 6.85. There was no caking and sticking 14 d after storage and the concentration of SA was ranged from 1.5×10⁹ to 2.0×10⁹ CFU/g. Safety test showed that there was no significant difference between the seedling emergence rate and the blank control in the range of 1 to 4 kg/667 m² of the dosage of SA, moreover, the seedling emergence of potato was affected to some extent at different time of 4 kg/667 m² SA. It was finally clear that potato seeds were not appropriate to put too long after mixing and been better sown within 2 days. Field experiments in more than two years demonstrated that the control efficacy of SA on potato verticillium wilt were ranged from 48.58% to 72.82%, and the yield increase rate were 5.52% to 14.32%. Comprehensive analysis showed that the SA could effectively control the occurrence of potato verticillium wilt, had obvious yield-increasing effect, and had broad application prospects.

Key words: Bacillus spp., seed-treating agent, potato verticillium wilt, control effect, yield increase, safety