Insecticides

Pertinent details

Carbofuran

Carbofuran, chemical name 2,3-dihydro-2,2-dimethyl-7-benzofuranyl N-methylcarbamate [52] , has a molecular formula C₁₂H₁₅N0_3, a relative molecular weight of 221.25 gmol^−1, and belongs to the class of insecticides called carbamates (CMs). As a systemic insecticide, when applied, it readily enters into a plant, gets transported by the sap, and feeding insects pick it up as they feed on the plants and become poisoned [52] . Like other CMs, the Carbofuran mode of actin involves reversible inhibition of cholinesterase enzyme activity in insects, mammals, and birds [52] [53] . For this reason, they were branded as anti-cholinesterases [52] . Cholinesterase enzyme is integral to all physiological responses and mechanisms, with no substitute enzyme thought to perform such an intricate set of functions in animals [52] . Thus, cholinesterase inhibition leads to a permanent overlay of acetylcholine neurotransmitters across a synapse [52] . Increased acetylcholine accumulation is associated with confusion, delirium, hallucinations, tremors, seizures, eventual collapse, and death [53] . Being a broad-spectrum insecticide, Carbofuran was dubbed an ideal insecticide, acaricide, and nematicide [52] .

Cypermethrin 10% EC

Cypermethrin, chemical name, ([cyano-(3-phenoxyphenyl)methyl] 3-(2,2-dichloroethenyl)-2,2-dimethy- lcyclopropane-1-carboxylate [24] , has molecular formula C₂₂H₁₉Cl₂NO₃ with a relative molecular mass of 416.3 mol⁻¹. Cypermethrin insecticide is a synthetic pyrethroid from natural pyrethrins extracted from plants, especially Chrysanthemum cinerariaefolium [54] [55] . Cypermethrin 10% EC is an emulsifiable concentrate (EC) formulation based on cypermethrin technical 10% w/w EC. It is a class II synthetic pyrethroid [55] [56] . Like other class II synthetic pyrethroids, an alpha-cyano group attached to the benzylic carbon in cypermethrin synergizes its toxicity [55] [56] . As reviewed by [55] , pyrethroids antagonize sodium voltage-dependent channels (SVDC) in insects. Furthermore, [55] shows that SVDC and potassium voltage-dependent channels (PVDC) are necessary for the movement of Na⁺ and K⁺ across the membrane, resulting in electrical impulses trailing along the neurons. The antagonism of SVDC downs the peak of Na+ ions and prolongs the SVDC opening time, all of which cripple neurotransmission [55] . When the insect absorbs the insecticide molecule through the cuticle, the neurotransmission ceases, gets paralyzed, and dies within a few seconds or minutes [55] .

Dimethoate

Dimethoate, chemical name, ([O, O-Dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate]), has a molecular formulaC₅H₁₂NO₃PS₂ with a relative molecular mass 229.3 g/mol. Dimethoate insecticide belongs to the class of organophosphorus insecticides and is used worldwide in agriculture and urban areas due to its high efficacy and rapid environmental degradation [43] . Unlike carbamates, organophosphates act in an irreversible way in insects, birds, and mammals to inhibit Acetylcholinesterase (AChE) activity, resulting in nerve damage, which may lead to death [43] [57] . AChE initiates the hydrolysis of acetylcholine (ACh), a neurotransmitter, into inactive choline and acetic acid [53] [58] . Inhibition of AChE leads to a buildup of ACh at the nerve synapses causing destabilization of AChE that is vital for a functioning central nervous system [53] [58] [59] . The increased levels of ACh in the synapses circumvents into permanent stimulation of the muscles, eventually leading to seizures, exhaustion, and possibly death .

Dimethoate is judged to be highly toxic to insects, although resistance has been observed in fruit fly species Bactrocera oleae, as reviewed by [43] .

Pestwin

Pestwin is a botanical pesticide blend of plant-derived insecticidal components, Azadirachtin indica, Pongamia pinnata, and Ricinus communis. This botanical concoction has been registered in Uganda by the Ministry of Agriculture, Animal Industry and Fisheries (MAAIF) [60] . Pongamia pinnata (also known as Karanj) is a tropical tree native to southeast Asia [61] , its oil is rich in medicinal properties and can be used as a biopesticide and insect repellent [61] . Although its seeds are highly rich in ricinoleic acid, a polyunsaturated fatty acidharvested for industrial work [62] , Ricinus communisis a castor bean plant whose toxicity is attributed to the presence of ricin, a water-soluble glycoprotein concentrated in seed endosperm but does not partition in seed oil [63] and is found in lesser concentration in other plant parts. Ricin is dubbed one of the most naturally poisonous and acts through the inactivation of a ribosome in the affected organisms [63] , which affects protein synthesis. Azadirachtin, a tetranortriterpenoid, is a chemical compound derived from neem and is a tremendous antifeedant and insect growth disruptor with negligible residual effect and minimal toxicity to biocontrol agents, predators, and parasitoids [46] [64] .

Pyrethrum ewc+

and Pyrethrum 5ew

Pyrethrum is a crude flower dust product extracted with organic solvents from mature inflorescence [55] of Chrysanthemum species. The natural active ingredient in pyrethrum extracts is pyrethrin. Pyrethrins are six related insecticidal esters occurring naturally in the crude material of Chrysanthemum flowers, formed by the combination of the acids, chrysanthemic and pyrethric acid, and the alcohols pyrethrolone, cinerolone, and jasmolone [55] [64] . As reviewed by [55] , the natural pyrethrin compound has a reduced photostability and is more biodegradable than the synthetic pyrethroids. Pyrethrins exert their toxic effects by disrupting voltage-gated SDVC and PVDC, which negates the Na⁺ and K⁺ ion exchange process in insect nerve fibers, which knocks down normal transmission of nerve impulses [55] [64] , causing paralysis. However, despite their rapid toxic action, many insects can digest pyrethrins quickly and, after a period of paralysis, recover instead of dying [64] . To increase their killing power, a synergist, piperonyl butoxide (PBO), can be added to natural pyrethrins [65] , which prevents insects from metabolizing pyrethrins and recovering from poisoning.

Pyrethrum ewc+ is an advanced natural insecticide oil in water formulated containing 21.9 g/L pyrethrin synergized with Sesame (Sesamum indicum) oils. It is a contact insecticide for use on all outdoor, protected crops and non-edible plants, such as ornamentals, to protect them against chewing and sucking pests throughout the season. This is a natural insecticide that contains 5% (w/v) pyrethrin. Conversely, Pyrethrum 5ew is a unique water-based formulation containing a blend of pyrethrum and natural food oils formulated to optimize natural Pyrethrum’s spectacular insect-killing power. Pyrethrum 5ew is a very crop-safe insecticide and can be used in a wide range of crops, including vegetables, fruits, coffee, cocoa, and broad acre crops such as maize and wheat.

Profenofos 40% + Cypermethrin 4% EC

This is a ready mix of Profenofos 40% and Cypermethrin 4% EC. Profenofos, chemical name [O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate], has a molecular formula C₁₁H₁₅BrClO₃PS, a molecular weight of 373.60 gmol⁻¹. Profenofos is an organophosphate insect that acts by inactivating AChE activity, accumulating ACh at the synapse junction, leading to neuronal dysfunction [66] . As stated above, Cypermethrin is a class II synthetic pyrethroid that modifies voltage-gated ion channels.