Multiple nonionic surfactants based on linear and secondary alcohol alkoxylates as well as alkyl polyglycosides, were evaluated as co-formulants for different biopesticides. Properties such as wetting performance, contact angle, and fungal and bacterial growth inhibition were evaluated. Eight different bacterial strains were tested (A. brasilense, B. amyloliquefaciens, B. firmus, B. licheniformis, B. subtilis subsp. subtilis, B. thuringiensis kurstaki, B. japonicum, P. putida) as well as two fungal species (Trichoderma harzianum and Cordyceps bassiana). In addition to surfactants, the compatibility of seed coating binders with these strains was evaluated for their potential use in seed coating formulations that may include bacteria and/or fungi. Significant differences were observed in the zones of inhibition (areas of the petri dish/nutrient were bacteria or fungi were unable to grow) measured for the different surfactants and seed coating binders tested. Many surfactants tested did not inhibit the microbial strains used, whereas some led to an inhibition zone diameter of up to 50% when compared to a traditional biocide. These differentiated effects could be attributed to the sensitivity of the microbes tested as well as to the surfactants themselves with different surfactant structures having a different impact on bacterial or fungal viability. Except for Trichoderma harzianium, the seed coating binders did not exhibit negative effects on the biological activity of the microorganisms.

Compatibility of surfactants and seed coating binders with bacterial and fungal strains

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