Biological Safety of the Molluscicidal Ingredient from Aspergillus fumigatus SL-30 Isolated from Rhizosphere of Phytolacca acinosa
GUO Dan-Zhao, CHEN Jun
2012, 30(6):
10-460-463.
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Objective To study biological safety of the molluscicidal ingredient（MI， a kind of diketopiperazines） in the exocellular broth of Aspergillus fumigatus SL-30’ which was isolated from the rhizosphere of Phytolacca acinosa. Methods The MI was prepared in concentrations ranging from 0.01 to 0.60 mg/L, at the same time molluscicidal activity against Oncomelannia hupensis was tested by using immersion method, and the LC50 in the case of immersion time for 24, 48 and 72 h was calculated. Acute toxicity of the MI with concentration ranging from 0.5 to 4.0 mg/L on Brachydanio rerio, Macrobrachium nippoensis and Rana limnochris was performed by standard laboratory procedure, and mortality rate of the tested animals with treated time of 24, 48 and 72 h was recorded. Effect of the MI on Eisenia fetida was tested using natural soil procedure with the dose of 1 and 10 mg/kg, and the poisoning performance and mortality in the 7th day and 14th day were recorded. Inhibition of the MI at 10 mg/kg on respiration of soil microorganisms was determined by sealed alkaline direct absorption method, and the released amount of CO2（mg/100 g） in the 2nd, 5th, 7th, 10th, 12th and 15th day was determined. Results Molluscicidal activity of the MI against Oncomelania hupensis was shown with LC50 0.101，0.062, and 0.022 mg/L in 24, 48 and 72 h, respectively. Mortality rate of Brachydanio rerio, Macrobrachium nippoensis and Rana limnochris all increased with the increase of MI concentration, and the LC50 of each kind of tested animals was recorded as follows: 1.941, 1.755 and 1.219 mg/L for Brachydanio rerio, 3.170, 2.720 and 2.419 mg/L for Macrobrachium nippoensis, 2.109, 1.751 and 1.288 mg/L for Rana limnochris in 24 , 48 and 72 h, respectively. The LC50 of MI on Eisenia fetida was >10.0 mg/kg. The inhibition rate of MI was less than 50% with a concentration of 10 mg/kg in 15 days. Conclusion The MI shows molluscicidal activity on Oncomelania hupensis with much lower toxicity on Brachydanio rerio, Macrobrachium nippoensis and Rana limnochrisn. The MI is safe to non-target aquatic organisms, and to both Eisenia fetida and soil microorganisms under the effective mollussicidal concentration.
