First report of the fungus Actinomucor elegans Benjamin & Hesseltine belonging to Odontotermes obesus (Rambur) (Isoptera: Termitidae) in India

摘要

Termites are pests notorious for causing grave damage to standing crops and buildings. Odontotermes obesus (Rambur) (Isoptera: Termitidae) is a commonly found species in the Indian subcontinent known to cause serious damage to crops. The fungus Actinomucor elegans Benjamin & Hesseltine is reported to have a ubiquitous distribution and been isolated from various hosts, as well as substrates. We have collected the isolates of A. elegans from the soil and dead termites present in the root zone of wheat plants in Haryana (India). The isolates were subjected to molecular analysis based on both morphological-and ITS (internally transcribed spacer) region and confirmed as A. elegans. After the identity verification, the pathogenicity of isolates against worker caste termites of O. obesus was tested by the topical application of an aliquot of the control or suitable suspension (0.5 mL) to the dorsum of each termite. The concentrations of the tested fungus A. elegans were 5 x 102 to 5 x 107 conidia mL-1, and their mortality against worker individuals of O. obesus was evaluated. Lethal time and concentrations were estimated. The assay was completely repeated three times. The results of the pathogenicity test revealed that A. elegans was highly pathogenic to worker caste termites of O. obesus, recording 90% mortality with 5 x 107 spores mL-1 and 94% mortality at 168 h. The median lethal concentration (LC50) and the median lethal time (LT50) of A. elegans were found to be 5.974 x 106 spores mL-1 and 108 h, respectively. Our results have provided new opportunities to control termites in agriculture, horticulture, and forest ecosystems. However, additional investigations both in controlled and field conditions are necessary, and when using A. elegans var. elegans, human safety also needs to be considered. Further investigations related to secondary compounds released by this fungus would add a new dimension to termite management strategies.