Studies on the Fungi Associated with Natural Death of Grasshopper Euprepocnemis plorans in Alfalfa, and its Uses as Biological Control in the Field

Abstract

Natural death of grasshopper Euprepocnemis plorans (Charp) has been observed in the field of alfalfa Medicago sativa L. in west Libyan Jamahiriya. Seven locations were surveyed, namely: Az-Zawia, Juddaim, Algheran, Tajura, Algarabulli, Alhirah, and Tarhuna. The highest mortality rate of 45.7% was in Juddaim, the lowest of 3% was in Algheran, and none-was recorded in Tarhunah, Algarabulli, and Alhirah. Many fungi were isolated from natural infected grasshopper and rate of natural death 66.60% of grass hopper was increased in infested alfalfa field with Bermuda grass compared with 45.70% in a newly alfalfa field, and identified as: Aspergillus parasiticus, Beauvaria bassiana, Fusarium sp., Helminthosporium sp., and Alternaria spp. The grasshopper is a major pest of the country, the use of the pathogenic fungus B. bassiana for its biological control was investigated. The effect of the fungus on the grasshopper in a non-sprayed naturally infested alfalfa field was evaluated. A suspension of the fungal spores at concentration of 1X10$^7$ conidia\ml was used as spray and as a mixed preparation with wheat bran. Applying the pathogen as a mixture with wheat bran was more effective than applying it in a spray in a liquid form due to the importance of B. bassiana with a wide host range in biological control, and the encouragement of natural enemies for pest control. Three pesticides (2 fungicide, 1 insecticide) were evaluated to determine whether they enhance or delay the growth of two fugal isolates for controlling (when necessary) use of chemical pesticides that effect natural biological enemies. All different concentrates of the pesticides used enhanced the fungal growth when submerging method was used compared to mixing methods, which lower the fungal growth except alfalfa fungal, isolate. the significant increases percentage in fugal growth range 2.27- 55.0% and decrease percentage 3.29-720 35% These results are important for integrated control of this insect.