Traditionally, game-keepers and agriculturalists have controlled predators using lethal methods, but there are circumstances under which these may be ineffective or inappropriate for animal welfare or conservation reasons. Generalised aversion is potentially a form of non-lethal control, in which predators are conditioned to avoid foul-tasting bait, causing them subsequently to generalise this avoidance to similar, but untreated, prey, thereby affording it protection. In this exploratory study, a group of captive red foxes (Vulpes vulpes) was successfully conditioned to avoid untreated milk after drinking milk containing BitrexTM, a bitter substance that they were unable to detect except by taste. Our foxes were members of a family group and so housed together to reduce stress, and therefore the individuals’ responses to the various treatments may not have been independent. As a result, we combined data from the three animals, and our most conservative analyses consider the sampling population to be this fox group; we do not make inferences about foxes in general, but confine them to this fox-group. This trial was a pilot to reveal the potential for future work on wild animals. Successful application of generalised aversion to non-lethal predator control has far-reaching implications for the sport hunting industry, nature reserve management and the conservation of threatened predators requiring control, as well as clear animal welfare benefits.

While the desire for systemic repellents is high, ineffective repellents put one at risk of insect-vectored pathogens. Vitamin B1, or thiamine, has been touted as a systemic insect repellent since 1943, and denounced as an ineffective placebo for just as long. This paper presents a scoping review of 104 relevant case reports, research studies, and review articles to trace the evolution of this idea and identify an evidence-based, scientific consensus. Reports of thiamine's systemic repellency are primarily anecdotal and based on uncontrolled trials and/or used bite symptoms as a proxy for reduced biting. Controlled experiments on insect landing and feeding found no evidence of repellency. Of the 49 relevant review papers, 16 insect bite prevention guidelines, and 4 government documents, none after the 1990s claimed thiamine is a repellent. The findings of this review are that thiamine cannot repel arthropods in any dosage or route of administration. Due to limited available evidence, the possibility that thiamine reduces the subjective symptoms of insect bites cannot currently be ruled out. Unfortunately, many medical professionals and travelers today still believe thiamine may be effective despite the evidence stating otherwise. Continued promotion of debunked repellents on the commercial market poses a serious risk in countries with the endemic, mosquito-vectored disease.

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is one of the most destructive pest species to have developed resistance to most chemical insecticides. We determined the composition and evaluated the potential of Tanacetum parthenium L. and Tanacetum vulgare L. (Asteraceae family) essential oil (EO) application as an alternative eco-friendly control strategy against L. decemlineata. We assessed the antifeedant activity for L. decemlineata larvae and adults by estimating the damage to potato leaves treated with three concentrations of EOs dissolved in ethanol (0.125, 0.25 and 0.5%). Results showed that T. parthenium EO was more effective against larvae, and T. vulgare was more effective against adults. In an olfactometer assay, the time required to choose an untreated leaf disc did not depend on the Tanacetum species, or life stage examined. However, the concentration of EO exhibited a significant effect on the behaviour of both developmental stages. At higher EO concentrations, both third instar larvae and adults require less time to choose an untreated leaf disc. Additionally, T. parthenium EO provoked more rapid movement away from the treated leaf disc than T. vulgare, especially at the highest concentration. Successful modification of L. decemlineata behaviour by the two Tanacetum oils suggests that they possess the potential for use in potato protection.

Attempts have been made in recent years to reduce the use of synthetic pesticides and seek alternative and innovative methods for pest control. We conducted a study on the chemical composition of Eucalyptus occidentalis essential oil and investigated the fumigant, contact and repellent effects against Tribolium castaneum (Herbst) (Col: Tenebrionidae) and Rhyzopertha dominica (F.) (Col: Bostrichidae). The major components were τ-cadinol (17.20), 1,8-cineol (15.5%), α-cadinol (14%) and α-pinene (9.21%). The contact toxicity experiment showed that the oil was more toxic to R. dominica (LD50 value 0.82 μL/cm) than to T. castaneum (LD50 value 0.99 μL/cm) and showed the same fumigant toxicity for both insects according to the 95% confidence limit of LC50. The repellency against T. castaneum was more than for R. dominica and increased from 14 to 75% for R. dominica and 22 to 78% for T. castaneum after 2 h. These results suggest that E. occidentalis essential oil is a potential candidate for use as a natural repellent and insecticide for stored-product insect pests.

Experiments were conducted in the laboratory to screen the leaf extract of Dracaena arborea (Willd.) Link for the presence of chemical groups with insecticidal activity against Sitophilus zeamais (Motsch.) and Callosobruchus maculatus (Fab.). The plant materials were collected, dried, ground to fine powder and extracted with 90% ethanol. Phytochemical screening involved the use of thin layer chromatography analysis for chemical compounds such as alkaloids, tannins, saponins, anthraquinones, flavonoids and terpenes. Partitioning of the extract was carried out by dissolving the extract in water to obtain the aqueous phase, which was partitioned between equal volumes of chloroform, n-hexane, n-butanol and ethyl acetate. The different fractions were screened for insecticidal activity against S. zeamais and C. maculatus. Some fractions of the leaf extract such as ethyl acetate and aqueous fractions demonstrated 100% mortality, offered protection to grains, reduced progeny development and repelled the insects compared with the control. Based on the activity of some fractions, the leaf extract of D.arborea has the potential for development as a botanical insecticide against S. zeamais and C. maculatus.

The ladybird beetle, Eriopis connexa (Germar) (Coleoptera: Coccinellidae), is one of the commonest predators of aphids (Hemiptera: Aphididae) in the cotton agroecosystem and in many other row and fruit crops in Brazil, and has been introduced into other countries such as the USA for purposes of aphid control. In addition, the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae) is the most serious cotton pest where it occurs, including Brazil. Controlling boll weevils and other pests such as cotton defoliators still tends to involve the intense application of insecticides to secure cotton production. The pyrethroid insecticide lambda-cyhalothrin (LCT) is commonly used, but this compound is not effective against aphids; hence, a desirable strategy would be to maintain E. connexa populations in cotton fields where LCT is applied. Using populations of E. connexa resistant (Res) and susceptible (Sus) to LCT, we compared behavioural responses on treated cotton plants and under confinement on partially and fully treated surfaces, and assessed the insects' survival on treated plants compared with that of the boll weevil. The E. connexa resistant population caged on treated plants with 15 and 75 g a.i. ha−1 exhibited ≫82% survival for both insecticide concentrations compared with ≪3% and ≪17% survival for susceptible E. connexa populations and boll weevils, respectively. The response of E. connexa Res and Sus populations when released, either on the soil or on the plant canopy, indicated avoidance towards treated plants, as measured by elapsed time to assess the plant. When compared with susceptible individuals, resistant ones took longer time to suffer insecticide knockdown, had a higher recovery rate after suffering knockdown, and spent more time in the plant canopy. Based on behavioural parameters evaluated in treated arenas, no ladybird beetles exhibited repellency. However, irritability was evident, with the susceptible population exhibiting greater irritability compared with the resistant population and a subgroup comprising resistant individuals that had recovered from knockdown. The outcomes for the E. connexa Res population indicate a promising strategy for its maintenance when using the insecticide LCT in integrated pest management schemes to control boll weevil or other non-target pest of ladybird beetles in cotton fields.

Although widely used, the term repellency needs to be employed with care when applied to ticks and other periodic or permanent ectoparasites. Repellency has classically been used to describe the effects of a substance that causes a flying arthropod to make oriented movements away from its source. However, for crawling arthropods such as ticks, the term commonly subsumes a range of effects that include arthropod irritation and consequent avoiding or leaving the host, failing to attach, to bite, or to feed. The objective of the present article is to highlight the need for clarity, to propose consensus descriptions and methods for the evaluation of various effects on ticks caused by chemical substances.

The structure of two compounds extracted from the leaves of Vitex negundo L., their repellent activity and toxicity against three strains of Tribolium castaneum (Herbst) were elucidated. Two compounds were purified and a residual film bioassay was used to evaluate the toxicity to adult T. castaneum. Mortality was recorded 24, 48 and 72 h post-exposure to compounds. The repellency activity of methanol extract was tested by using nine concentrations. Each dose was applied on a half circle of the filter paper, keeping the other part untreated. Insects released on treated filter paper were assessed for repellency up to 5 h. Two bioactive compounds, 22,23-dihydro-α-spinasterol-β-d-glucoside and salicylic acid were isolated from the methanolic leaf extracts by column chromatography and thin-layer chromatography. Their structures were elucidated by various spectroscopic methods. Compound 22,23-dihydro-α-spinasterol-β-d-glucoside is the first report from this plant. Both compounds showed insecticidal activity and the leaf extracts caused 100% repellency in the three tested strains of T. castaneum. Both compounds showed toxicity to T. castaneum, but compound 22,23-dihydro-α-spinasterol-β-d-glucoside was more potent. Its potential future use as herbal insecticide against T. castaneum is discussed.

The tropical warehouse moth Ephestia cautella (Walker) is an important storage pest of maize grain. The control of this major moth pest relies heavily on the use of synthetic insecticides. We assessed the biological efficacy of a commercial neem oil (Calneem oil) against E. cautella in the laboratory, using the common grain protectant Actellic as a positive control. Contact toxicity, repellency, effects on oviposition, development and grain damage were assessed. The assays were conducted by treating 100 g of maize grains with Calneem oil concentrations of 3, 5 and 7 ml/l; and Actellic at 2 ml/l. Calneem oil significantly (P < 0.05) reduced oviposition rate, development of eggs and immature stages, and emergence rate of E. cautella progeny in maize grains. Grains treated with Calneem oil had significantly (P < 0.05) reduced grain damage in storage, and the oil had a repellency of 53–70% compared with the negative control. Calneem oil protected maize grain against damage by E. cautella for 10 weeks, compared with 20 weeks protection by Actellic. There was no resistance development to the oil for three generations of E. cautella. The insects that survived treatment with the LC90 concentration (12.2 ml/l) of the Calneem oil laid fewer eggs, and some of their progeny were deformed. Calneem oil provided a good level of protection to maize grains against infestation by E. cautella, and may therefore be a suitable substitute for Actellic.

Insect pests cause major damage to stored grain and foodstuffs, reducing the products' weight, quality and market value. Eight spices commonly used to add flavour and colour to food were evaluated, singly and in combination, for their contact and fumigant toxicity, repellency and effects on progeny development against the cowpea weevil Callosobruchus maculatus F. and rust red flour beetle Tribolium castaneum Herbst. The powders of large cardamom, turmeric and ginger showed contact toxicity against the two test insects. Green cardamom powder was found to have fumigant toxicity against adults of both insects. Clove powder at 1.5 g/50 g dose showed 100% repellency against adults of T. castaneum. The powders of large cardamom, cinnamon and clove caused complete inhibition of progeny production in C. maculatus and T. castaneum at a dose of 5 g/100 g. A 1:1 mixture of green cardamom and turmeric showed both contact and fumigant toxicity against C. maculatus, while a mixture of clove and large cardamom showed repellency and inhibited progeny development in T. castaneum.

l-menthol isolated from the essential oil of Mentha arvensis and seven of its acyl derivatives were tested for contact and vapour toxicity, and ovicidal and repellent activity against the storage pests Callosobruchus maculatus F., Rhyzopertha dominica F., Sitophilus oryzae L. and Tribolium castaneum Herbst. Menthyl propionate and l-menthol were highly toxic in contact assays and vapour toxicity assays respectively. l-menthol was also found to be strongly repellent (82–100% at 0.353 μg/cm2 dose) against all the insects, while menthyl acetate was highly ovicidal against T. castaneum.

1,8-cineole, one of the components of the essential oil of Artemisia annwa, was evaluated for repellency and toxicity against three stored product coleopterans—Callosobruchiis maculatus F. (Coleoptera: Bruchidae), Rhyzopertha dominica F. (Coleoptera: Bostrychidae) and Sitopliilus oryzae L. (Coleoptera: Curculionidae). It was found to be moderately repellent to all three species, with a mean repellency in the range of 65–74% at the highest dose tested (4.0 μl/ml) within 1h. A contact toxicity assay revealed that direct topical application was more effective than using impregnated filter paper. The compound was more effective as a fumigant and gave 93–100% mortality against all the three pest species at the dose of 1.0 μl/l air under empty jar conditions as compared to treatment of jars filled with grain (11–26% mortality). The lethal dose and lethal concentration required to kill 50% of the beetles (LD50 and LC50) respectively varied.with the toxicity assay method. LD50 values of 0.03, 0.04 and 0.04 μl/insect against C. maculatus, R. dominica and S. oryzae respectively were found in the topical application assay while the LC50 in the fumigant assay was 0.28, 0.33 and 0.46 μl/l against C. maculatus, R. dominica and S. oryzae respectively.

Résumé: —L'un des composés de l'huile essentielle d'Artemisia annua, le 1,8-cineole, a été évalué pour sa répulsion et sa toxicité vis à vis de trois coléoptères des denrées stockées, Callosobrnchus maculatus F. (Coleoptera: Bruchidae), Rhyzoperta dominica F. (Coleoptera: Bostrychidae) et Sitopliilus orizae L. (Coleoptera: Curculionidae). Il s'est avéré être modérément répulsif pour les 3 espèces, avec une répulsion moyenne de 65–74% à la plus forte dose testée (4.0 ml/ml) pendant 1 heure. Un essai de toxicité de contact indique qu'une application locale directe est plus efficace que l'utilisation d'un papier filtre imprégné. Le composé est plus efficace en fumigation et provoque 93–100% de mortalité chez les trois espèces de ravageurs à la dose de 1.0 ml/l d'air dans un pot vide par rapport à un pot rempli de grains (11–26% de mortalité). La dose létale et la concentration létale requises pour tuer 50% des scarabées (LD50 et LC50 respectivement) varient avec le type d'essai de toxicité. Des valeurs de LD50 de 0.03, 0.04 et 0.04 ml/insecte pour C. maculatus, R. dominica et S. oryzae respectivement ont été trouvées dans l'essai avec une application locale alors que la LC50 dans l'essai de fumigation était respectivement de 0.28, 0.33 et 0.46ml/l pour C. maculatus, R. dominica et S. oryzae.

The essential oil extracts of six Malaysian plants, i.e. Curcuma longa, Zingiber officinale, Pandanus odorus, Cinnamomum zeylanicum, Syzygium aromaticum and Cymbopogon citratus, were evaluated for repellent activity against Periplaneta americana using a modification of the ‘two-cylinders’ method. Dose-dependent repellency ranging from 57.1 to 100% was exhibited by all six extracts at the lowest concentration tested (12 ppm).

Several terpenoids and oils were screened for vapour toxicity and repellency against the termite, Odontotermes brunneus. In toxicity tests, knockdown time KT50 and KT90 values were derived at 5 mg/cm2. For repellency screening, a new experimental setup was designed and effective time ET50 and ET90 values were determined at 2 mg/cm2. Among the compounds screened, eucalyptus oil produced the fastest knockdown (KT50 24.8 min) while β-ionone was found to be the least effective (KT50 536.0 min). Terpeneol (anhydrous) afforded maximum persistence of 338.0 min, whereas the least persistence was obtained from linalool (78.9 min) which prevented 50% of the population from crossing over the treated barrier (ET50).

The toxic and repellency effects of four plants Chenopodium procerum, Ocimum canum sinus, Tetradentia riparia and Capsicum frutescens were tested on Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman. The toxic effect was found on leaves of Ocimum canum sinus and Chenopodium procerum Hochst. The four plants tested did not show any repellency effect on the bruchids.

Tanzanian strains of Tribolium castaneum (Herbst), Gnatocerus maxillosus (F.), Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky were confined to maize grain treated with a dilute dust of permethrin at the rates of 1.5, 3.0 and 6.0 ppm active ingredient. The adult mortality and resulting F1 generation were recorded. G. maxillosus was very susceptible to the insecticide and even the lowest dose brought complete control. T. castaneum adults survived all treatments but few F1 were produced. Adult survival of s. oryzae and S. zeamais was progressively reduced by increasing dosage, although S. zeamais was much less susceptible to the treatment than S. oryzae.

The repellency of grain, treated with 3.0 ppm permethrin, to S. oryzae, S. zeamais and T. castaneum was tested in a simple choice chamber. Neither male nor female T. castaneum were repelled but significantly fewer eggs were laid on treated grain. For both Sitophilus spp there was no significant difference between the numbers of females or eggs observed on treated or untreated grain, but males were repelled from permethrin.

The importance of these results is discussed in relation to a recent recommendation that the treatment of shelled grain with 3.0 ppm permethrin should be adopted in Tanzania in order to control Prostephanus truncatus (Horn), a new and serious storage pest.