Abstract:
Objective Efficacies of fungicides in preventing and controlling the disease on tree plants caused by Exobasidium vexans were determined.
Method In vitro antifungal activity of 4 chemical pesticides, 5 biopesticides, and mixtures of them against E. vexans mycelial growth were tested. Treatments included the applications of 45 agents by pairing 5 of the pesticides in the mass ratios of 1∶4, 1∶1, 2∶3, 3∶2, and 4∶1 in 9 categories to evaluate the synergistic fungicidal effect.
Result The application of 70% thiophanate-methyl wettable powder or 1% shenqinmycin suspension concentrate showed the lowest EC50 of 0.0076 mg·L−1 and 0.2941 mg·L−1, respectively, of the individual pesticides in inhibiting E. vexans growth. Of the 45 paired compounds, 31 exhibited synergisms. The 1∶4 combination of the mixture of 10 parts of water-soluble pine needle powder to one part of the microemulsion of 0.2% Psoralea corylifolia L. seed extract had the strongest synergistic interaction index of 427.6730. There were 12 pairings exerted varying additive effects and two antagonistic on each other.
Conclusion The most effective fungicides used singly for controlling E. vexans were 70% thiophanate-methyl wettable powder and 1% shenqinmycin suspension concentrate. The greatest synergism between the paired pesticides was found in a 1∶4 ratio of the 10∶1 water-soluble pine needle powder and the microemulsion of 0.2% Psoralea corylifolia L. seeds extract.
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