Insecticidal activity of Tithonia diversifolia and Vernonia amygdalina

Abstract

The diversity of synthetic pesticides has been reduced through regulation especially in the European Union leading to a resurgence of interest in natural plant products for pest control. Here we investigated two Asteraceae species, Tithonia diversifolia and Vernonia amygdalina that are used by farmers in Africa in bio rational pest control to determine the chemical basis of activity against pests of stored legumes and identify plant compounds with commercial potential. The cowpea beetle, Callosobruchus maculatus, an ubiquitous pest of African stored grain legumes, was exposed to extracts of both plant species at 10, 1 and 0.1% w/v and fractions of these extracts at representative concentrations. Extracts and fractions were toxic to recently emerged adults, but did not reduce oviposition by those females that survived. The sesquiterpene, Tagitinin A, was isolated from one of the active fractions and identified using H1 and C13-NMR and shown also be toxic to C. maculatus and so partially explains the activity of the whole plant. Other compounds in the active fractions were identified, at least to structural class, using high resolution mass spectroscopy (HRESI-MS). Sequiterpenes and flavones were common to fractions from both plants. Stigmostane steroidal saponins were the most abundant secondary metabolites in V. amygdalina.

Bioactivity of Common Pesticidal Plants on Fall Armyworm Larvae (Spodoptera frugiperda)

“…Low mortality (<40%) was a lso observed with Vernonia amygdalina Delile followed by Aloe vera (L.) Burm.f. and Trichilia emetica Vahl, despite evidence of efficacy against other target insect pests [11,[18][19][20][21]. The most effective plant species were Azadirachta indica A.…”

“…Initial plant screening was carried out with ten pesticidal plant species: A. indica, O. basilicum, N. tabacum, C. citratus, T. vogelii, A. vera, L. camara, T. emetica, V. amygdalina and L. javanica. Considerable phytochemical and efficacy knowledge was recorded by our group and others on all the material used of these species [10,15,17,18,20,24,[32][33][34][35][36][37] which were sourced from the same locations with samples from four locations around Mitundu, Lilongwe District, Malawi combined to control for potential chemical variation across space [37,38]. The leaves of all plant species were collected from the wild from these known locations.…”

Efficacy of homemade botanical insecticides based on traditional knowledge. A review

“…A major constituent of marigold tree essential oil, the monoterpenoid α-pinene, has insecticidal and repellent activities against coleopteran storage pests (Huang et al 1998;Moronkola et al 2006). Sesquiterpene lactones in tree marigold have been shown to be toxic to the coleoptera Callosobruchus maculatus (Green et al 2017).…”

“…Sesquiterpene lactones with insecticidal activities against coleopteran pests and with repellent activities against lepidopteran pests have been isolated from bitter leaf (Ganjian et al 1983;Green et al 2017).…”

Opportunities and Scope for Botanical Extracts and Products for the Management of Fall Armyworm (Spodoptera frugiperda) for Smallholders in Africa

“…Another species investigated in this study included Tephrosia vogelii, a rotenoid producing and widely used species for pest control in Africa but this was not active suggesting a level of tolerance in FAW to the insecticidal rotenoids occurring in this species [23,87]. Another South American plant which grows widely as an invasive weed in Africa where it has been shown to have biological activity against insects [88] and used widely as a pesticide is Tithonia diversifolia but again this species was not active [23]. The most promising plant species based on their low mammalian toxicity, abundance and bioactivity against FAW identified through this work were Lippia javanica, Ocimum basilicum and Cymbopogon citratus which showed various activities including anti-feedancy and increased mortality.…”