Effects of neem leaf extracts on Lepidopteran pest species attacking Solanum macrocarpon L. (Solanaceae) in southern Togo

Abstract

Lepidopteran pests cause considerable damage to Solanum macrocarpon Linnaeus (Solanaceae). Their control by the use of botanical extracts is a promising alternative to improper use of chemical insecticides. The objective of this study was to evaluate the effects of three doses of leaf extract of the neem tree, Azadirachta indica Adrien-Henri de Jussieu (Meliaceae) against Lepidopteran pest species that attack S. macrocarpon L. in southern Togo. The experimental design used for the study was randomized complete blocks with three replicates and five treatments: three doses (N1: 300, N2: 600 and N3: 900 L/ha) of neem leaf aqueous extract, a synthetic insecticide "Cydim Super" (C.S.) and a Control (C) in field. Botanical exctract and synthetic insecticide were applied after Lepidopteran pest species frequency and number collected once a week for 8 weeks. The yield data were obtained by weighing the aerial parts (leaves and stems) of S. macrocarpon harvested. Three species of Lepidoptera (Selepa docilis Butler (Noctuidae), Spoladea recurvalis Fabricius (Crambidae) and Scrobipalpa ergasima Meyrick (Gelechiidae)) were recorded. The neem leaf extract reduced frequency and numbers of all the three species found on S. macrocarpon than Control. S. recurvalis and S. ergasima were not recorded on plots treated with N3: 900 l/ha. No Lepidopteran pest species was recorded on plots treated with synthetic insecticide. S. macrocarpon yields obtained on plots treated with neem leaf extract N1, N2 and N3 were higher (5.42 ± 1.80 t/ha, 7.39 ± 1.88 t/ha and 6.97 ± 0.96 t/ha, respectively) than that of synthetic insecticide which was 3.51 ± 0.72 t/ha.

Efficacy of neem bio-pesticide and synthetic insecticides against control of fall armyworm (Spodoptera frugiperda) in Maize

“…These results agree with the discoveries by Anyim et al [5] which showed that insecticidal application significantly increased yields of different crops. Abla & Seth [16] found that yield of Solanum macrocarpon plants sprayed with medium and high doses of the neem leaf extract were higher than those plants sprayed with the synthetic insecticide (Cydim Super). In this study, both neem bio-pesticide and synthetic insecticides were found to be effective in controlling the FAW.…”

“…Bio-pesticides are usually considered to be more target-specific and inherently less toxic than synthetic insecticides hence limiting their impact on non-target species, such as other insects, birds and mammals. They usually are biodegradable in the natural environment, thus reducing exposure to environmental pollution and chances of developing insect resistance [16] . Among the botanical biopesticides currently under study for commercialization, neembased bio-pesticides are one of the least toxic to humans, shows very low toxicity to beneficial organisms and promising for the control of many insect pests [18] .…”