Synergistic effects between Regalia^® and other fungicides in controlling cucumber powdery mildew and lettuce downy mildew
H. SU (1)
(1) Marrone Bio Innovations, Inc., Davis, CA, U.S.A.
Phytopathology 100:S123

Regalia^® is a biofungicide formulated from extract of giant knotweed (Reynoutria sachalinensis) and effectively controls common fungal and bacterial diseases. Combination (tank mix) of Regalia^® and other commercial fungicides can be an effective and efficient measure in increasing pathogen control efficacy and managing fungicide resistance in pathogens. Greenhouse and growth chamber experiments were conducted to evaluate the efficacy of Regalia^® in combination with commonly used chemical and biological fungicides in controlling cucumber powdery mildew (Sphaerotheca fuliginea) and lettuce downy mildew (Bremia lactucae). The results show a statistically significant synergistic effect with Regalia^® in a tank mix with azoxystrobin (Quadris^®), myclobutanil (Rally^® 40W), quinoxyfen (Quintec^®), or triflumizole (Procure^®) in controlling powdery mildew on cucumber in repeated tests. Only an additive effect with no synergy was found with tank mixes of Regalia^® with Bacillus subtilis (Serenade^®), or Bacillus pumilus (Sonata^®), cyprodinil (Vangard^®), or kresoxim-methyl (Sovran^®) in non-repeated tests. Synergistic effect was also found when Regalia^® was applied in combination with acibenzolar-S-methyl (Actigard^®) to control lettuce downy mildew. The results clearly show that Regalia^® can be effectively applied with other fungicides either in a tank mix or a rotation to increase efficacy and/or reduce the risk of fungicide resistance.