Pyrethroids1 are among the most potent insecticides known. They are synthetic compounds structurally derived from pyrethrin I, one of the six active components of pyrethrum, which is an extract from the dried flower heads of Chrysanthemum cinerariaefolium. The natural pyrethrins have excellent insecticidal properties and low mammalian toxicity, but are of limited use because of their low photostability and high biodegradability (Wouters and van den Bercken 1978). However, pyrethroids are relatively stable, have a high toxicity to a wide spectrum of insects (Elliott 1976), are relatively nontoxic to mammals (Elliott 1976), and have tremendous agricultural potential (Harris and Turnbull 1978). Moreover, pyrethroids are much less persistent than the organochlorine insecticides, such as DDT and dieldrin, and apparently do not accumulate in the environment.

Effects of synthetic pyrethroid insecticides on nontarget organisms.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=7383&context=rtd

Sorption of organophosphorus and carbamate insecticides by soil

Influence of temperature on knockdown, toxicity, and resistance to pyrethroids in the house fly, Musca domestica

Chlorpyrifos is an organophosphorus insecticide used to control insect pests in soil. The fate of chlorpyrifos in soils under different moisture regimes is of interest because application directions specify soil-surface treatments for a number of agricultural and urban pests. Chlorpyrifos was degraded rapidly in all air-dry soils and slightly more slowly in soils at field capacity and/or under submerged conditions. Degradation rates were influenced by clay-catalysed hydrolysis under air-dry conditions and neutral or alkaline hydrolysis under submerged conditions. Degradation was faster in Bellary soil (chromic haplustert) and slower in Chettalli soil (ustic palehumult) under all three moisture regimes. The calculated half-lives ranged from 1.6 to 10.0, 5.2 to 22.0 and 8.7 to 25.1 days under air-dry, field capacity and submergence respectively at an application rate of 10 mg kg -1 .

Persistence of Chlorpyrifos in Soils under Different Moisture Regimes

Laboratory tests were conducted to determine the effects of five pyrethroid insecticides—permethrin (FMC 33297) [3-phenoxybenzyl (±)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate]; FMC 45498 [(S)-α-cyano-3-phenoxybenzyl-(R)-cis-2-(2,2-dibromovinyl)-3,3-dimethylcyclopropanecarboxylate]; Shell WL 41706 [(±)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropane-carboxylate]; Shell WL 43467 [(±)-α-cyano-3-phenoxy benzyl (±)-cis,trans-2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropanecarboxylate]; and Shell WL 43775 [(±)-α-cyano-3-phenoxybenzyl (±)-2-(4-chlorophenyl)-3-methylbutyrate]—at 0.5 and 5μg/g on microbial populations and activities in a sandy loam. The insecticides had antimicrobial activity in early stages of incubation. The populations recovered after 2 to 4 weeks and stimulatory effects on populations were also observed in later stages. No inhibition of acetylene (C2H2) reduction was evident with any of the insecticides. However, WL 43467 at both concentrations and permethrin and WL 41706 at 5 μg/g increased nitrification after 4 weeks. Soil microbial respiration, as indicated by oxygen consumption, increased with increasing concentration of insecticides, suggesting the possibility of microbial degradation of the insecticides. Dehydrogenase activity showed that none of the insecticides inhibited formazan (2,3,5-triphenyltetrazolium formazan) formation, whereas urease activity was stimulated in most cases. The studies indicated that some of the pyrethroid insecticides may exert transient effects on populations and activities of the microflora in a sandy loam, but these were short-lived and minor in nature.

Influence of five pyrethroid insecticides on microbial populations and activities in soil.

The spectrum of contact toxicity and activity in soil of four pyrethroid insecticides was assessed in the laboratory. Pyrethroids tested were: FMC 33297 (3-phenoxybenzyl (±)-3-(2, 2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate); Shell WL 41706 (alpha-cyano-3 phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate); Shell WL 43467 (alpha-cyano-3-phenoxybenzyl 2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropane-1-carboxylate); and Shell WL 43775 (alpha-cyano-3-phenoxybenzyl-2-(4-chlorophenyl)-3-methyl-1-butyrate). Chlorpyrifos and carbofuran, two broad spectrum contact and soil insecticides were included for comparative purposes. Spectrum of contact toxicity was determined using 24–48 h nymphs of the common field cricket, Acheta pennsylvanicus (Burmeister), 24–48 h onion maggot adults, Hylemya antiqua (Meigen), 3rd instar dark sided cutworms, Euxoa messoria (Harris), northern corn rootworm adults, Diabrotica longicornis (Say), and honeybees, Apis mellifera L. Crickets were used to assess insecticidal activity in soil relative to soil moisture, type, and temperature. The pyrethroids were effective contact insecticides comparable in toxicity and spectrum of activity to chlorpyrifos and carbofuran. They were particularly toxic to the darksided cutworm. They were less effective in mineral soil than chlorpyrifos. WL 43467 showed activity in mineral soil close to that of carbofuran, while the other pyrethroids were less active. Activity in soil was influenced by soil moisture and type. In contrast to the standard insecticides the pyrethroids generally showed a negative temperature coefficient of toxicity in soil.

Laboratory studies on the contact toxicity and activity in soil of four pyrethroid insecticides

The effectiveness of 16 experimental compounds as soil insecticides was assessed under laboratory conditions. Chlorpyrifos, carbofuran, and dieldrin were included as standard insecticides. Spectrum of activity as contact insecticides was determined using 24–48 h nymphs of the field cricket, Acheta pennsylvanicus (Burmeister), 24–48 h onion maggot adults, Hylemya antiqua (Meigen), third stage darksided cutworms, Euxoa messoria (Harris), northern corn rootworm adults, Diabrotica longicornis (Say), and honeybees, Apis mellifera L. First stage crickets were used to assess the biological activity of experimental compounds relative to soil type, moisture, and temperature and also their volatility in moist sand and persistence of biological activity over a 48 week period. All of the insecticides showed broad spectrum contact activity. Twelve showed fair to very good potential in soil. Four insecticides, Shell WL 24794 (O,O-dimethyl-S-1-[3-(5-methyl-1,2,4-oxadiazolyl)] ethyl phosphorodithioate), Shell WL 25735 (O-[2-chloro-1-(2,5-dichlorophenyl) vinyl] O-methyl methylphosphonothioate), Shell WL 26738 (O-[1-(2,4-dichlorophenyl) vinyl] O-methyl ethylphosphonothioate), and chlorpyrifos-methyl showed good potential. Two others, Counter® (S-[(tert-butylthio) methyl] O,O-diethyl phosphorodithioate) and Shell WL 24073 (O-[2-chloro-1-(2,5-dichlorophenyl) vinyl] O-methyl ethylphosphonothioate) were considered to have very good potential as soil insecticides.

S. A. Turnbull

Papers

Laboratory studies on the contact toxicity and activity in soil of four pyrethroid insecticides

Laboratory assessment of the potential of 16 experimental compounds as soil insecticides

Contact toxicity of twenty-one insecticides to adults of the carrot rust fly (diptera: psilidae)