Compatibility of biocontrol agent formulas and synthetic fungicides in controlling maydis leaf blight on corn caused by Bipolaris maydis

Maydis leaf blight caused by Bipolaris maydis is one of the limiting factors in increasing maize production. The application of biological control agents (BCAs) as a biopesticide to control pests and plant diseases expected to decrease synthetic fungicide usage and its impacts. Several researches showed that the formula of Bacillus subtilis biopesticide suppress the development of several plant diseases including maydis leaf blight in maize. Nevertheless, biological control agents cannot completely replace the need for chemical fungicides in the agro-ecosystem. Therefore, this study was carried out to evaluate the effect and compatibility of several synthetic fungicides with antagonistic bacterial formulas in controlling B. maydis on maize. Five types of synthetic active ingredients used were difenoconazole, propinep, fluopicolide, metalaxyl, and dimethomorph. From the results of laboratory tests, 3 types of active ingredients with the highest inhibitory effectiveness be selected for the field test. Field treatments were arranged using a Randomized Block Design with 2 factors, factor I was biological control agents with 2 levels (T0 = without biological control agents, T1 = with biological control agents) and factor II was synthetic fungicide with different active ingredients with 4 levels (S0 = no synthetic fungicide, S1=diphenoconazole, S2=propinep, S3 = fluopicolide). Each treatment combination was repeated 4 times. The result showed that all the synthetic fungicides tested were compatible with the biological control agent. Fungicide with active ingredient of diphenoconazole was the most compatible with the BCAs showing the lowest disease severity value of 27%, while control treatment conditions without BCAs was 72%.