Contact toxicity of some fixed plant oils and stabilized natural pyrethrum extracts against adult maize weevils (Sitophilus zeamais Motschulsky)

The contact toxicity of some selected fixed plant oils and stabilized natural pyrethrum (Chrysanthemum cinerariaefolium) blends against adult maize weevils (Sitophilus zeamais) were investigated. Natural pyrethrum extract was stabilized against ultraviolet (UV) light by blending with fixed oils extracted from Azadirachta indica A. Juss (neem tree); Thevetia peruviana (yellow oleander) and Gossypium hirsutum L. (cotton) seeds. Cottonseed oil had the highest stabilization effect on the pyrethrum blend exposed to UV light of 366 nm. The results indicated that the natural pyrethrum extract blended with cottonseed oil was the most potent against maize weevils and that the potency was concentration-time dependent. Cottonseed and neem seed oils enhanced the stabilization of the natural pyrethrum insecticide

Botanical insecticides, deterrents, and repellents in modern agriculture and an increasingly regulated world.

Botanical insecticides have long been touted as attractive alternatives to synthetic chemical insecticides for pest management because botanicals reputedly pose little threat to the environment or to human health. The body of scientific literature documenting bioactivity of plant derivatives to arthropod pests continues to expand, yet only a handful of botanicals are currently used in agriculture in the industrialized world, and there are few prospects for commercial development of new botanical products. Pyrethrum and neem are well established commercially, pesticides based on plant essential oils have recently entered the marketplace, and the use of rotenone appears to be waning. A number of plant substances have been considered for use as insect antifeedants or repellents, but apart from some natural mosquito repellents, little commercial success has ensued for plant substances that modify arthropod behavior. Several factors appear to limit the success of botanicals, most notably regulatory barriers and the availability of competing products (newer synthetics, fermentation products, microbials) that are cost-effective and relatively safe compared with their predecessors. In the context of agricultural pest management, botanical insecticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and postharvest protection of food in developing countries.

Genotoxic effects of pentachlorophenol, lindane, transfluthrin, cyfluthrin, and natural pyrethrum on human mucosal cells of the inferior and middle nasal conchae.

BACKGROUND: Animal experiments and epidemiological studies suggest that pentachlorophenol (PCP) and gamma-hexachlorocyclohexane (lindane) should be classified as possible human carcinogens. In the past, both have had a variety of applications in the civilian and military sectors and in forestry. They have, e.g., been used to impregnate and treat uniforms and other fabrics and to control human lice. Animal experiments indicate that PCP in particular causes mutations and chromosome aberrations and thus DNA damage. Studies on whether or not this also applies to newer substances and especially to natural type I and type II pyrethroids still are not available. What is particularly lacking are data on the genotoxic effects of these substances on human target cells. Our study describes the genotoxic effects of PCP, lindane, transfluthrin, cyfluthrin, and natural pyrethrum on human mucosal cells of the inferior and middle nasal conchae. METHODS: Epithelial cells were isolated from nasal mucosa, which was removed in the surgical treatment of chronic sinusitis and nasal concha hyperplasia. After the cells had been tested for vitality using the trypan blue exclusion test, the short-term culture method was used. The material was incubated with PCP (0.3, 0.75, and 1.2 mmol), lindane (0.5, 0.75, and 1.0 mmol), transfluthrin (0.05, 0.1, 0.5, 0.75, and 1.0 mmol), cyfluthrin (0.05, 0.1, 0.5, 0.75, and 1.0 mmol), natural pyrethrum (0.001, 0.005, 0.01, 0.05, and 0.1 mmol), and N-methyl-N'-nitro-N-nitrosoguanidine for 60 minutes. Substance-induced DNA damage (single-strand and double-strand breaks) were determined using single-cell microgel electrophoresis. A fluorescence microscope was used together with an image processing system to analyze the results obtained. RESULTS: After exposure to all tested substances, a high percentage of the cells of the middle nasal concha in particular were found to have severely fragmented DNA as a result of strong genotoxic effects. Although the reaction of the cells of the inferior nasal concha was significantly less strong (p < 0.001), the tested substances were nevertheless found to have a notable genotoxic effect on these cells too. CONCLUSION: Our study strongly suggests that exposure to PCP, lindane, transfluthrin, cyfluthrin, and natural pyrethrum has a genotoxic effect on the epithelial cells of human nasal mucosa. In addition, we have shown that nasal structures differ in susceptibility to the various pesticides used in the tests. Thus, the study provides new evidence supporting the biological plausibility of PCP- and lindane-induced effects, thereby helping evaluate potential PCP- and lindane-induced mucous membrane carcinomas of these parts of the nose. In addition, our study shows that other substances that today are widely used for controlling pests have a considerable genotoxic effect on human target cells. The results obtained indicate the need for additional studies on the genotoxicity of these substances and their adverse effects on human health.

The effects of phytochemical pesticides on the growth of cultured invertebrate and vertebrate cells.

A range of cultured cells of invertebrate and vertebrate origin was grown in the presence of a number of phytochemical pesticides to test the effect of the latter on cell proliferation. The main observation was that azadirachtin was a potent inhibitor of insect cell replication, with an EC50 of 1.5 x 10(10) M against Spodoptera cells and of 6.3 x 10(9) M against Aedes albopictus cells, whilst affecting mammalian cells only at high concentrations (> 10(-4) M). As expected, the other phytochemical pesticides, except for rotenone, had little effect on the growth of the cultured cells. Rotenone was highly effective in inhibiting the growth of insect cells (EC50:10(-8) M) but slightly less toxic towards mammalian cells (EC50:2 x 10(-7) M). Neem terpenoids other than azadirachtin and those very similar in structure significantly inhibited growth of the cell cultures, but to a lesser degree. The major neem seed terpenoids, nimbin and salannin, for example, inhibited insect cell growth by 23% and 15%, respectively.

Interactions between pesticides and components of pesticide formulations in an in vitro neurotoxicity test.

Organophosphate (OP) pesticides are often used in combination with one another and with the components of formulations. Evidence already exists for interactions in the neurotoxic effects of OPs through interference with metabolism, but there is also potential for interactions related directly to cell damage. The purpose of this work was to investigate this possibility for OPs and the components of one of their common formulations in vitro. NB2a neuroblastoma cells were induced to differentiate in the presence of the OPs diazinon and chlorpyrifos, in combination with a commercial formulation (identified as Commercial Formulation 1) of the compounds and, independently, the components of that formulation. The compounds were tested in pairs in various proportions and the resulting inhibition of neurite outgrowth was measured by light microscopy and quantitative image analysis. Interactions were determined in terms of enhanced or reduced effects of the paired compounds in comparison with the expected additive effects estimated from the effects of each compound on its own. Synergism was detected between combinations of: 10 microM chlorpyrifos and 500 nM pyrethrum; chlorpyrifos and one of the solvents (regular spirit) found in Commercial Formulation 1. All other combinations of OPs and products were additive in their neurotoxicity. The data suggest that exposure to multiple OP-containing pesticide formulations may lead to synergistic neurotoxicity by a direct mechanism at the cellular level.

[Insecticidal properties of sumitrin]. / Insektitsidnye svoistva sumitrina

The study of insecticidal properties of sumitrin demonstrated that in contact action it was a highly effective insecticide; in topical application LD50 for domestic flies, bedbugs and cockroaches was 0.47, 1.25 and 3.26 mug/g, respectively. Sumitrin possessed high action selectivity for insects and low toxicity for warm-blooded animals (LD50 for albino mice greater than 7500 mg/kg). In the form of aerosols sumitrin and its mixtures with DDVF were less active than compositions on the neopinamine base.

Toxicity of natural pyrethrins and five pyrethroids to fish.

The toxicity of natural pyrethrins and five pyrethroids was determined with coho salmon (Oncorhynchus kisutch), steelhead trout (Salmo gairdneri), fathead minnow (Pimephales promelas), channel catfish (Icatlurus punctatus), bluegill (Lepomis macrochirus), and yellow perch (Perca flavescens). The 96-hour LC50's in static tests at 12 degrees C ranged from 24.6 to 114 mug/l of natural pyrethrins and from 0.110 to 1,140 mug/l of pyrethroids. Two pyrethroids, RU-11679 and SBP-1382 (R), were over 10 times more toxic than pyrethrum extract in the flow-through tests. Coldwater species of fish were more sensitive than warmwater species to all the compunds. Temperature (12-22 degrees C) influences the toxicity of natural pyrethrin and the pyrethroids. The natural pyrethrin was more toxic to fish in pH 6.5 than in pH 9.5 water, but the toxicity of pyrethroids was not influenced in the pH range. The two most toxic pyrethroids, RU-11679 and SBP-1382, Were deactivated more rapidly in water solutions than natural pyrethrins, S-bioallethrin, dimethrin, and d-trans allethrin.

Toxicity of paired mixtures of candidate forest insecticides to rainbow trout.

The toxicities of Zectran, Dylox, Volaton, Guthion, pyrethrum extract, and the synthetic pyrethroids SBP-1382, and RU-11679 were determined individually and in paired mixtures against rainbow trout. The carbamate Zectran was the least toxic, and the synthetic pyrethroids were the most toxic. Nine of the mixtures produced less than additive toxicity (antagonism), nine produced additive toxicity, and two produced greater than additive toxicity (synergism). None of the mixture toxicities deviated markedly from additive,and only two pairs of mixtures would pose a greater toxicological hazard to fish than the respective individual chemicals.

Investigation on the acute toxic effect of pyrethrum on the blood glucose and of glucose administration on the acute pyrethrum toxicity in Meriones hurrianae Jerdon (Rodentia).

The effect of different doses of pyrethrum on the blood glucose level and glucose tolerance in pytethrum-administered gerbils, were investigated. Pyrethrum produces hyperglycemia and lowers the glucose tolerance indicating an impairment in the uptake and utilization of glucose. The possible reasons for these effects are discussed.

Pyrethroid insecticides: esterase cleavage in relation to selective toxicity.

The ester group of primary alcohol chrysanthemates is cleaved by mouse hepatic microsomal esterases, more rapidly for the (+)-trans than for the (+)-cis isomers. Substrate-specificity and inhibition studies in vivo establish that these pyrethroid-hydrolyzing esterases probably contribute to the low mammalian toxicity of bioresmethrin and other (+)-trans chrysanthemate insecticide chemicals derived from primary alcohols.

Development of new synthetic pyrethroids.

The insecticidal activity of synthetic pyrethroids was compared with that of the natural pyrethrins, which have been used on a world-wide scale as active ingredients for insecticidal aerosols or mosquito coils.All of the synthetic pyrethroids were found to be more stable than the pyrethrins. Tetramethrin showed a very high knock-down effect and resmethrin showed a remarkable kill effect in oil-based formulations. The efficacy of a suitable formulation of a mixture of tetramethrin and resmethrin surpassed that of natural pyrethrins synergized with piperonyl butoxide. For mosquito coils, allethrin and prothrin were superior to the natural pyrethrins in both kill and knock-down effects.Optically active synthetic pyrethroids always showed superior knock-down activity and higher killing activity than optically inactive compounds.