The Toxicity, Persistence and Mode of Actions of Selected Botanical Pesticides in Africa against Insect Pests in Common Beans, <i>P. vulgaris</i>: A Review

Abstract

Common beans are affected by many insect pests such as bean leaf beetle, aphids, legume pod borer and bean beetles. Traditional and cultural practices such as site selection, crop rotation, intercropping and seed selection, sowing date are used to reduce the infestation of insect pests of common beans in the field and in storage rooms. Natural enemies such as predators, parasitoids and pathogens can control the insect pests. Synthetic pesticides such as cypermethion, carbaryl, and lambda-cyhalothrin have reported to be effective, but are toxic to people, destroy natural enemies and contaminate the environment. Botanical pesticides are the promising alternatives. This review paper explains toxicity, persistence and mode of actions of active ingredients of botanical pesticides. Rotenone from T. vogelii has the oral lethal dose (LD50) of 132 -1500 mg/kg to mammals. It delays the electron transport chain in mitochondria of the insects and limits the cellular energy production. Azadirachtin is antifeedant and growth disruptor of insects. It has low toxicity to mammals. The oral LD 50 in mammals is greater than 3540 mg/kg. Azadirachtin displays strong effects on chemoreceptors of the insects. Pyrethrins are axonic poisons and have repellent effects to insects. It is less toxic to mammals with the LD 50 of about 1500 mg/Kg. It attacks the nervous systems of insects. Sesquiterpene lactones from T. diversifolia, Pentacyclic triterpenoids from Lantana camara, Vernodalin, Vernodalol and Epivernodalol from V. amygdalina have repellent and feeding deterrents chemicals which discourage the insects from feeding the crop. Most active ingredients of botanical pesticides have short life span in the environment.

Different Plant Extracts against <i>Phytophthora infestans</i> (Mont.) de Bary in Tomato <i>in Vitro</i>

“…Such results are very promising and may be used in the future to develop potential can-didate pesticide in controlling P. infestans in tomato and potato. Reseach evidence has shown the presence of different active compounds with antifungal and antibacteril properties in Plectranthus barbatus [19], Lantana camara [33] and Sphaeranthus species [20].…”

Neem Oil and Crop Protection: From Now to the Future

“…Currently, most of the botanical insecticides that are being studied and that are effective against many pests are those with feeding deterrent action, so their indiscriminate use could result in the development of resistance ( Tangtrakulwanich and Reddy, 2014 ; Mpumi et al, 2016 ). Feng and Isman (1995) evaluated the behavior of two lines of Myzus persicae , which were exposed to pure azadirachtin or to refined neem seed extract at the same concentration as azadirachtin.…”

Additive Effect of Botanical Insecticide and Entomopathogenic Fungi on Pest Mortality and the Behavioral Response of Its Natural Enemy

“…The active components in pyrethrum are highly labile in ultraviolet (UV) light, non-persistent, and are less toxic to humans and the environment [9,[16][17][18]. Although the lack of persistence has previously limited use of natural pyrethrum as an agricultural insecticide [8,15] it is less disruptive to IPM programs that include beneficial insects than conventional insecticides.…”