A standardized bioassay using the yellow dung fly, Scathophaga stercoraria L. (Diptera: Scathophagidae), was developed to test the lethal and sublethal toxicity of parasiticide residues in livestock dung. The repeatability of the bioassay was assessed for the parasiticide ivermectin in 13 tests performed by seven laboratories in Germany, the United Kingdom, Switzerland, and Canada. Test results had an acceptable range of heterogeneity. The calculated median effective concentration for 50% (EC50) egg-to-adult mortality was 20.9 +/- 19.1 microg ivermectin/kg dung fresh weight (FW) (mean +/- standard deviation; range, 6.33-67.5 microg/kg). Mortality was not observed below a calculated no-observable-effect concentration (NOEC) of 8.1 +/- 7.7 microg/kg FW. However, prolonged development time (and, in a subset of tests, reduced body size) was observed above a calculated NOEC of 0.8 +/- 0.8 microg/kg FW. An oviposition site choice test revealed that yellow dung fly females do not discriminate among dung of different ivermectin concentrations. Thus, the yellow dung fly is suitably sensitive, and the methods are sufficiently repeatable, to support use of this standardized bioassay by the international community in the registration of new veterinary pharmaceuticals.
Wireworms, the soil-dwelling larvae of click beetles (Coleoptera: Elateridae), comprise major pests of several crops worldwide, including maize and potatoes. The current trend towards the reduction in pesticides use has resulted in strong demand for alternative methods to control wireworm populations. This review provides a state-of-the-art of current theory and practice in order to develop new agroecological strategies. The first step should be to conduct a risk assessment based on the production context (e.g., crop, climate, soil characteristics, and landscape) and on adult and/or larval population monitoring. When damage risk appears significant, prophylactic practices can be applied to reduce wireworm abundance (e.g., low risk rotations, tilling, and irrigation). Additionally, curative methods based on natural enemies and on naturally derived insecticides are, respectively, under development or in practice in some countries. Alternatively, practices may target a reduction in crop damage instead of pest abundance through the adoption of selected cultural practices (e.g., resistant varieties, planting and harvesting time) or through the manipulation of wireworm behavior (e.g., companion plants). Practices can be combined in a global Integrated Pest Management (IPM) framework to provide the desired level of crop protection.
Wireworms are yellowish soil-dwelling larvae that damage a wide range of arable crops. The most common wireworms found in European cultivated fields (except for the Caucasus) belong to the genus Agriotes (Coleoptera: Elateridae). In several European countries, environment-impacting insecticides are applied on a prophylactic basis to control them. However, before any treatment can be applied, European legislation requires that an assessment is done when pest population levels exceed a damage threshold. The threshold substantially depends on wireworm species, thus quick reliable larval identification is needed to implement the appropriate integrated pest management practices. Furthermore, research into non-chemical strategies involves carrying out tests with live and identified wireworms. Thus, thousands of wireworms were observed in a bid to identify live larvae so that larval density could be assessed and compared with species-specific thresholds before sowing, and laboratory experiments were carried out. This work led to a horizontal identification table that allows for quick and accurate identification of live larvae. This key, unlike traditional dichotomous keys, simultaneously considers a set of multiple discriminating morphological characters in order of stability. The key can be reliably used by less experienced users and, once minimum familiarity is acquired, most larvae can be identified rapidly, with high precision.
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