Impact of Environment on Callosobruchus maculatus (Coleoptera: Chrysomelidae) Response to Acetone Extract of Gnidia kaussiana Meisn (Thymeleaceae) and Ocimum canum Sims (Lamiaceae) Botanical Insecticides

Abstract

The response of pests to the effects of a botanical insecticide can vary spatially and temporally. To test whether efficacy of botanicals differed spatially, the insecticidal efficacy of Gnidia kaussiana and Ocimum canum against Callosobruchus maculatus was investigated in two different agro-ecological zones of Cameroon, i.e. Maroua and Ngaoundéré (sudano-sahelian and sudano-guinean zones, respectively). Experiments were, therefore, conducted to determine the insect mortality, progeny production, grain damage and weight loss in cowpea. G. kaussiana was more effective against C. maculatus in Maroua (LD50 = 0.12 g/kg at 6th day of exposure) than in Ngaoundéré (LD50 = 4.35 g/kg at 6th day of exposure). Moreover, it was more toxic than O. canum extract and neem seed oil (reference), irrespective to the agro-ecological zones. Overall, the performance of O. canum did not vary significantly between the two zones, and was slightly more active (LD50 = 4.66 g/kg) than the reference insecticide neem seed oil (LD50 = 4.89 g/kg) in Ngaoundéré in contrast to the results recoded in Maroua (LD50 = 1.44 g/kg and 2.60 g/kg, respectively for neem seed oil and O. canum at 6 days post exposure). In view of the above, there were some discrepancies in extract performance between Maroua and Ngaoundéré. Thus, the establishment of dose rates of insecticidal products formulated from G. kaussiana must be specific to an environment in contrast to those from O. canum.

Fractionated Extracts From Gnidia kraussiana (Malvales: Thymeleaceae) as Bioactive Phytochemicals for Effective Management of Callosobruchus maculatus (Coleoptera: Chrysomelidae) in Stored Vigna unguiculata (Fabales: Fabaceae) Seeds

“…Callosobruchus maculatus were collected in Mokolo market, Mayo-Tsanaga division in far north Cameroon. ‘One hundred parent stocks of C. maculatus collected from untreated infested cowpea stocks were introduced into 500 g of sterilized cowpea in rearing medium and kept in the laboratory’, as described in the previous study ( Kosini et al 2020 ). They were reared for two generations and freshly emerging adults were selected from the culture and used for the experiment.…”

“…In the developing countries, 15–25% postharvest loss occurs during storage ( Abass et al 2014 ); storage loss due to insect pest infestations being a problem of major concern ( Hengsdijk and Boer 2017 ). Cowpea ( Vigna unguiculata ) (L.) Walp seeds known in developing countries as the ‘meat of poor people’ ( Kosini et al 2020 ) are heavily damaged by insect pests during storage ( Deshpande et al 2011 ). Seed loss is generally due to the different immature stages of Callosobruchus maculatus (F.), which develop inside the seeds ( Kosini et al 2017 ).…”

Impact of Plant Extracts on the Pollination Activity of <i>Apis mellifera</i> Linnaeus, 1758 (Hymenoptera: Apidae) on Flowers of Cowpea Variety Feekem, in Dang (Adamaoua, Cameroon)

“…mellifera are frequently recorded on the cowpea flowers. In Cameroon, although many natural additives based on plant extracts have proven effective against harmful insects [11,14,38], their effects on pollinating insects in particular Ap. mellifera remains less known and it is necessary to carry out studies in the Adamaoua Region (Cameroon) on the effect of local plants on the foraging behavior of Ap.…”

Seed Yield Improvement in Vigna unguiculata (L.) (Fabaceae): Efficiency of Pollinators and Impact of Aqueous Leaf Extract of Three Plant Species in North Cameroon

“…The relationships between floricultural plants and their pollinators have been intensively studied in Cameroon [3,16]. However, in the northern savannah region of the country, despite the diversified flora and a flourishing market gardening activity, there is very little information on the insecticidal potential of the local plant species extracts against pest insects [17], except few works, for example those on leaf extract of Gnidia kaussiana Meisner (Myrtyales: Thymeleaceae) and Ocimum canum Sims, 1824 (Lamiales: Lamiaceae) against Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae) [18] and that on aqueous extracts of Cassia occidentalis L. (= Senna occidentalis (L.) Link, 1829), Eucalyptus camaldulensis Dehnh., 1832 and Hyptis suaveolens (L.) Poit., 1806 on the entomofauna and the seed yield of Gossypium hirsutum L., 1753 [19]. In short, nothing is said about the insecticidal aptitude of common wild plant species, easily accessible and exploitable as botanical pesticides against crop pests, able to replace synthetic pesticides.…”