Influence of water management, application timing and temperature on efficacy of MTB-951, a mycoherbicide using Drechslera monoceras to control Echinochloa crus-galli L.

MTB-951 is a potential mycoherbicide using a fungal plant pathogen ( Drechslera monoceras ) isolated from native Echinochloa species in Japan. Conidia of this pathogen were used as the active ingredient and its herbicidal performance was examined in a greenhouse. The efficacy of MTB-951 on Echinochloa crus-galli L. was higher in deep water (7–9 cm) than in relatively shallow water (3–5 cm). In a postemergence application, the efficacy decreased as the leaf stage of E. crus-galli proceeded between the 1 and 2.5 leaf stage. For example, the control ratio (%) of E. crus-galli was 95% when applied at the 1 leaf stage, and 72% at the 2.5 leaf stage in 5 cm water. Generally, mycoherbicidal efficacy was less when applied pre-emergence rather than postemergence. Efficacy was also influenced by the duration of submergence in deep water. For example, when water depth was kept at 5 cm for more than 7 days after application and then decreased down to 3 cm, the efficacy was high. However, when the water depth was kept at 5 cm for less than 7 days, the efficacy was low. Efficacy was lower under high temperatures (35°C/25°C, day/night) than under low temperatures (25°C/15°C, day/night). Water management, application timing and temperature are important factors on herbicidal efficacy of MTB-951 to control E. crus-galli .     

Effect of temperature on herbicidal properties of MTB-951, a mycoherbicide to control Echinochloa crus-galli L.

MTB-951 is a potential mycoherbicide using a fungal plant pathogen ( Drechslera monoceras ) isolated from native Echinochloa species in Japan. Conidia of this pathogen were used as the active ingredient and the effect of temperature on its properties was examined in a laboratory. The optimum temperature for conidium germination was broad between 15 and 35°C and no difference in the germination ratio existed within this temperature range. Mycelial growth was the fastest at 25°C but was slower outside of the range 15–35°C. When leaves of Echinochloa crus-galli L. were immersed in deionized water containing the conidia, cellular electrolyte leakage from the leaves was observed. However, no electrolyte leakage occurred from leaves of rice ( Oryza sativa L.) under the same conditions. The occurrence of electrolyte leakage from E. crus-galli was dependent on the temperature and was the highest at 25°C. Herbicidal activity of MTB-951 against E. crus-galli was high between 25°C and 30°C, but decreased at 35°C in a glass vessel. In the present study, it was revealed that the physiological and herbicidal properties of MTB-951 depended on the temperature.     

Effect of δ-aminolevulinic acid on the herbicidal efficacy of foliar-applied MTB-951, a mycoherbicide to control Echinochloa crus-galli L.

The conidia of a plant pathogen ( Drechslera monoceras [Drechsler] Subram. et Jain [=  Exserohilum monoceras [Drechsler] Leonard et Suggs]), MTB-951, which was isolated from native Echinochloa species in Japan, were used as the herbicidal active ingredient. The effects of δ-aminolevulinic acid (ALA) on the efficacy of foliar-applied MTB-951 on Echinochloa crus-galli L. were examined. First, foliar-applied MTB-951 exhibited almost no efficacy when no dew period was provided. However, the efficacy increased depending on the length of the dew period. MTB-951 and ALA exhibited an additive effect on E. crus-galli under 3 day dew conditions, although they exhibited a significant synergistic effect under no-dew conditions. When the leaves of E. crus-galli were immersed in deionized water containing the conidia of MTB-951, cellular electrolyte leakage from the leaves was observed. The ALA increased the electrolyte leakage by MTB-951 synergistically. Also, ALA increased the number of lesions on the leaves of E. crus-galli caused by MTB-951 under light conditions but failed to increase the number under dark conditions. These results suggest that ALA promotes infection with MTB-951 for E. crus-galli through its photodynamic action.