Evaluation of biocontrol efficiency of different Bacillus preparations and field application methods against Phytophthora blight of bell pepper

Biocontrol efficiency of various Bacillus preparations (BB11 and FH17 strains, and a mixture of both strains (BF) at a 1:1 ratio by concentration) and different application methods against Phytophthora blight of bell pepper were studied. The application methods included (A) mixing (mixing BF with rapeseed residue and then immediately applying in the field), (B) composting (mixing BF with rapeseed residue and made compost before application), (C) spraying (spraying diluted BF into field or rhizosphere of plants), and (D) watering (watering diluted BF into field or rhizosphere of plants). In greenhouse experiments, the addition of BF increased biocontrol efficiency (60.3%), and yield increase (200%) was better than with BB11 (55.8 and 80.6%, respectively) or FH17 (37.1 and 50.0%, respectively). In field trials at Huai’an in 2001, the best dosages of BF mixture (1010 cfu/ml) with the four above-mentioned application methods were 15, 7.5, 15, and 22.5 L/ha, respectively. When preparations were applied at the best dosage in the same field, the BF mixture provided superior biocontrol efficiency and greater yield increase with treatment B than those with treatment A or C. Combining the field trial results from 2002 to 2003 at Huai’an and Wu’han, the total average control efficiencies and yield increases for treatments A, B, and C reached 81.0, 88.0, and 79.1% and 33.1, 44.3, and 29.1%, respectively, with their best dosages. However, method B, composting, provided better disease control and greater yield increases than all other methods, and did so at a lower application rate.