Pest Management Science

Three DNA‐based genotyping techniques, bi‐directional PCR amplification of specific allele (bi‐PASA), single‐stranded conformational polymorphism (SSCP) and minisequencing, have been developed and compared for the detection of the S291G (insensitive acetylcholinesterase) and L1014F (insensitive sodium channel) mutations associated with azinphos‐methyl and permethrin resistance, respectively, in the Colorado potato beetle (Leptinotarsa decemlineata). Extraction of genomic DNA from individual neonates that were hatched from previously collected egg masses is the most efficient and reliable means to obtain suitable templates in terms of convenience, economy, speed and DNA quality. Bi‐PASA, employing two allele‐specific primers, appears to be the most efficient and rapid genotyping method for the simultaneous detection of both resistant/susceptible homozygous (SS, RR) and heterozygous (SR) alleles. Its resolution, however, is strongly dependent on the quality of template genomic DNA. SSCP also allows unambiguous genotyping, including the detection of heterozygous alleles, and is less dependent on template DNA quality, but requires a longer processing time. Minisequencing is amenable to a 96‐well microtiter plate format for the processing of a large number of samples and allows direct detection of resistant/susceptible homozygous alleles but is not as efficient as the PASA and SSCP in detecting heterozygous alleles. In considering the advantages and disadvantages of each technique, DNA‐based genotyping is best employed in combinations, with the bi‐PASA as the primary method and the SSCP and minisequencing as the secondary validating methods. These methods are rugged, rapid, cost‐effective and capable of resolving SS, RR and SR individuals. The availability of such DNA‐based genotyping techniques, using neonate genomic DNA as templates, will enable the precise monitoring of the resistant and susceptible allele frequencies, including those of heterozygote individuals, in field populations of L decemlineata.

© 2001 Society of Chemical Industry

Sweet pepper is now grown, in tropical and subtropical areas, under the integrated pest management (IPM) tactic of ‘physical barrier’, whereas it was once grown primarily in open fields. This management tactic, when properly employed, has the advantage of eliminating many of the larger open‐field pests, and has resulted in greatly increased pepper yields. However, certain other pest populations are exacerbated by this IPM tactic. This paper reviews the primary pests and current control tactics in sweet pepper. Copyright © 2007 Society of Chemical Industry

Resistance to the bacteria‐derived insecticides spinosad (Conserve), abamectin (Vertimec), Bacillus thuringiensis var kurstaki (Btk) (Dipel), B thuringiensis var aizawai (Bta) (Xentari), B thuringiensis crystal endotoxins Cry1Ac and Cry1Ca, and to the synthetic insecticide fipronil was estimated in a freshly‐collected field population (CH₁ strain) of Plutella xylostella (L) from the Cameron Highlands, Malaysia. Laboratory bioassays at G₁ indicated significant levels of resistance to spinosad, abamectin, Cry1Ac, Btk, Cry1Ca, fipronil and Bta when compared with a laboratory insecticide‐susceptible population. Logit regression analysis of F₁ reciprocal crosses indicated that resistance to spinosad in the CH₁ population was inherited as a co‐dominant trait. At the highest dose of spinosad tested, resistance was close to completely recessive, while at the lowest dose it was incompletely dominant. A direct test of monogenic inheritance based on a back‐cross of F₁ progeny with CH₁ suggested that resistance to spinosad was controlled by a single locus. Copyright © 2004 Society of Chemical Industry

Strobilurins are one of the most important classes of agricultural fungicide. Their invention was inspired by a group of fungicidally active natural products. The outstanding benefits they deliver are currently being utilised in a wide range of crops throughout the world. First launched in 1996, the strobilurins now include the world's biggest selling fungicide, azoxystrobin. By 2002 there will be six strobilurin active ingredients commercially available for agricultural use. This review describes in detail the properties of these active ingredients – their synthesis, biochemical mode of action, biokinetics, fungicidal activity, yield and quality benefits, resistance risk and human and environmental safety. It also describes the clear technical differences that exist between these active ingredients, particularly in the areas of fungicidal activity and biokinetics.

© 2002 Society of Chemical Industry

Ecological backlashes such as insecticide resistance, resurgence and secondary pest outbreaks are frequent problems associated with insecticide use against arthropod pest species. The last two have been particularly important in sparking interest in the phenomenon of insecticide‐induced hormesis within entomology and acarology. Hormesis describes a biphasic dose–response relationship that is characterized by a reversal of response between low and high doses of a stressor (e.g. insecticides). Although the concept of insecticide‐induced hormesis often does not receive sufficient attention, or has been subject to semantic confusion, it has been reported in many arthropod pest species and natural enemies, and has been linked to pest outbreaks and potential problems with insecticide resistance. The study of hormesis remains largely neglected in entomology and acarology. Here, we examined the concept of insecticide‐induced hormesis in arthropods, its functional basis and potential fitness consequences, and its importance in arthropod pest management and other areas. © 2013 Society of Chemical Industry

BACKGROUND: Knowledge of the impact of insecticides on Tetranychus urticae Koch and its predator Phytoseiulus persimilis Athias‐Henriot is crucial for IPM. This study evaluates the effect of thiamethoxam on T. urticae and its predator by considering different routes of exposure (topical, residual and contaminated food exposures) and their combinations.

RESULTS: Thiamethoxam effects on T. urticae were higher when residual and contaminated food exposures were considered. The total effect was higher than 90% where contaminated food exposure was involved. On P. persimilis, the total effect was higher in residual and contaminated prey exposures compared with topical exposure, and all combinations of routes of exposure attained a total effect higher than 90%.

CONCLUSION: Thiamethoxam was found to be toxic to T. urticae and P. persimilis; however, the impact of the insecticide depended on the routes of exposure and their combinations. Lethal and sublethal effects occurred in residual and contaminated food exposures, while only sublethal effects occurred in topical exposure of predators and prey. The toxicity of thiamethoxam on prey and predator increased with the number of exposure routes involved. By limiting exposure to thiamethoxam to ingestion of contaminated food only, the impact of the pesticide was more favourable to P. persimilis than to its prey. Copyright © 2010 Society of Chemical Industry

The insecticidal activities of essential oil extracts from leaves and flowers of aromatic plants against fourth‐instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Myrtus communis L were found to be the most toxic, followed by those of Origanum syriacum L, Mentha microcorphylla Koch, Pistacia lentiscus L and Lavandula stoechas L with LC₅₀ values of 16, 36, 39, 70 and 89 mg litre⁻¹, respectively. Over 20 major components were identified in extracts from each plant species. Eight pure components (1,8‐cineole, menthone, linalool, terpineol, carvacrol, thymol, (1S)‐(−)‐α‐pinene and (1R)‐(+)‐α‐pinene) were tested against the larvae. Thymol, carvacrol, (1R)‐(+)‐α‐pinene and (1S)‐(−)‐α‐pinene were the most toxic (LC₅₀ = 36–49 mg litre⁻¹), while menthone, 1,8‐cineole, linalool and terpineol (LC₅₀ = 156–194 mg litre⁻¹) were less toxic.

© 2002 Society of Chemical Industry

BACKGROUND: The insecticidal activity of essential oil of Mentha piperita L. emend. Huds. against local mosquitoes as disease vectors was recognized and found to be due to the presence of menthol, which is the major aroma compound of the oil. The minor compounds of the oil, i.e. menthone, β‐caryophyllene, menthyl acetate, limonene, α‐pinene and pulegone, showed either less or no activity against the mosquitoes tested. L‐Menthol derivatives were synthesized and their knockdown effect and mortality were evaluated against local mosquitoes of Culex quinquefasciatus Say, Aedes aegypti L. and Anopheles tessellatus Theobald as disease vectors. This is the first report of mosquitocidal activity of menthol and its derivatives against Cx. quinquefasciatus, Ae. aegypti and An. tessellatus.

RESULTS: Derivative synthesis followed by structure–activity relationship studies identified several derivatives, i.e. menthyl chloroacetate, menthyl dichloroacetate, menthyl cinnamate, menthone glyceryl acetal, thymol, α‐terpineol and mugetanol, with enhanced mosquitocidal activity against Cx. quinquefasciatus, Ae. aegypti and An. tessellatus relative to the parent compound L‐menthone.

CONCLUSION: In ester derivatives of L‐menthol the optimum activity is dependent on the size and shape of the ester group and the presence of chlorine atoms in the ester group. In structurally related derivatives of L‐menthol the optimum activity is dependent on the aromaticity, the degree of unsaturation, the position of the hydroxy group and the type of functional group. Copyright © 2007 Society of Chemical Industry