Efficacy of Botanical Insecticides against the Pea Aphid, <i>Acyrthosiphon pisum</i> (Harris) and Effect on Some of Its Natural Enemies on Field Pea in South Central Ethiopia

Abstract

A field experiment was conducted at Kulumsa center of the Ethiopian Institute of Agricultural Research (EIAR) during September 2011 and January 2011 to assess the efficacy of botanical insecticides against the pea aphid, Acyrthosiphon pisum and their effect on the commonly associated natural enemies of the pest. Aqueous extracts of different parts of four plant species, namely Trev.), young leaves of Blue Gum (Eucalyptus A. Juss) and matured leaves of Aloe ( concentrations (5 and 10%) were tested along with the standard insecticide Pirimicarb 50% WP and untreated check on pea aphid tolerant variety (Tegegnech) and susceptible variety (Mohanderfer). The experiment was laid out in randomized complete block design with three replications. The lowest and highest aphid population and damage level were recorded from the standard insecticide (Pirimicarb) and untreated plots, respectively. Aphid population and their damage in botanical treatments were intermediate between the standard and the untreated check. Eucalyptus globulus resulted in lower aphid population and damage level than the re of botanical treatments. Similarly, the lowest and highest yield were recorded from the untreated and Pirimicarb treated plots, respectively. Differences between any of the botanical and Pirimicarb treatments were not significant for yield ( 0.51 to 0.81 tons/ha higher yield than the untreated check. This corresponds to a yield advantage of 21.1 to 33.5% over the untreated control. Aphid population in variety 'Tegegnech' was similar to that of the 'Mohanderfer' but damage seve rate (10 %) resulted in lower pest populations, less damage and higher yield than the low rate (5 %). Predation and parasitism were relatively high in the untreated plots, intermediate in botanical treated plots and low in Pirimicarb treatments suggesting that botanicals were safer to the natural enemies of the pest

Evaluation of Five Different Botanical Extracts Against Some Pests and Predators in Laboratory Conditions

“…Other botanicals also proved their toxicity in causing mortality against C. septempunctata, as 10% concentration of M. azedarach leaf extract caused 31.05±0.527 mortality after 96 hours of study. Highest concentration (10%) of E. globulus leaf extract caused 25.69±0.546 mortality, which is somewhat similar to the results of Gemmeda and Ayalew (2015), who found toxic effects of eucalyptus against ladybird beetle while M. oleifera leaf extract stood medium effective against C. septempunctata population causing 28.52±0.645 mortality. The results from the second experiment regarding mortality of A. andersoni (Figure 4) showed that 10% concentration of N. tabacum leaf extract caused 51.55±1.19 mortality, followed by 10% of M. azedarach leaf extract 46.49±0.724 mortality as compared to work of Castagnoli et al (2002) which observed 46% mortality of predatory mites by using bakain leaf extracts.…”