The Synergism and Larvicidal efficacy of microalgae Fischerella muscicola extracts and Nestor against meal moth Plodia interpunctella larvae

Abstract

To develop bioinsecticides from environmentally friendly natural products, the present study was conducted to assess the toxicity of ethanol and aqueous extracts of the microalga Fischerella muscicola and the pesticide Nesto each separately, based on the LC50 values of concentrations (10, 25, 50, 75 and 100 μg/ml), in addition to Estimation of the synergy ratios of these extracts with Nestor at a ratio of 1:1 and 1:5 (pesticide:extract) against third and fifth instar larvae of Indian meal moth Plodia interpunctella, after 24, 48 and 72 hours of surface treatment. The results proved that the ethanolic extract had a very toxic effect on larvae, as it recorded a significant superiority in toxicity to the pesticide Nestor, as the LC50 values against third instar larvae were 0.018, 0.028 and 0.042 μl/larva, and LC50 values for fifth instar larvae were 0.113, 0.074 and 0.047 μl/l 24, 48, and 72 hours of working time, respectively. The values of the synergy ratios indicated that the extracts of the alga Fischerella had a synergistic effect with the insecticide Nestor clearly in increasing the toxicity against the larvae when they were mixed with the insecticide in both proportions, as the killing rates increased with the increase in the mixing ratio, which was manifested by a significant decrease in the LC50 values, especially in the aqueous extracts. It alone recorded any killing rates after 72 hours of treatment, while it gave high killing rates when mixed with the pesticide, especially at a ratio of 1:1. Accordingly, a number of active phenolic compounds present in algae extracts were identified, qualitatively and quantitatively, using High Performance Liquid Chromatography (HPLC) technology. The crude ethanolic extract (40.19%) and Kaempferol in the crude aqueous extract (44.1%).