The intensive use of only one mode of action for many years is risky, because even pest insects with a low intrinsic resistance risk may develop resistance. Therefore, resistance strategies need to include several control options for pest insects needing regular treatments.
Pyrethroid-resistant beetles dominate in Western and Central Europe and are becoming established in the North and East, the main oilseed-rape-growing areas of Europe. The development and spread of pyrethroid-resistant pollen beetles highlights the need for effective management strategies for oilseed rape insect pests.
Identification of arthropod predators is challenging when closely related species are found at a given locality. Identification of the immature stages is especially problematic, because distinguishing morphological features are difficult to use or have not been described. We used polymerase chain reaction (PCR) to distinguish closely related carabids and spiders, and to match eggs and larvae (or nymphs) with identified adult parents. Within the Carabidae, we amplified species-specific mitochondrial cytochrome oxidase I (COI) fragments for three species each in the genera Poecilus and Harpalus, and two each in Chlaenius and Bembidion. Within the Araneae, we amplified species-specific COI fragments for two Hibana species (Anyphaenidae), Pardosa milvina and Rabidosa rabida (Lycosidae), Frontinella communis and Grammonota texana (Linyphiidae), and Cheiracanthium inclusum (Miturgidae). We are able to correctly identify all immature stages tested--eggs, larvae (or nymphs) and pupae--by comparison of the amplified fragments with those of the adults. Using COI markers as species identifiers is a tenet of the Barcode of Life initiative, an international consortium to provide a molecular identifier for every animal species.
Crop seeds are often treated with pesticides before planting. Pesticide-laden dust particles can be abraded from the seed coating during planting and expelled into the environment, damaging nontarget organisms. Drift of these dust particles depends on their size, shape and density. In this work, we used X-ray micro-CT to examine the size, shape (sphericity) and porosity of dust particles from treated seeds of various crops. The dust properties quantified in this work were very variable in different crops. This variability may be a result of seed morphology, seed batch, treatment composition, treatment technology, seed cleaning or an interaction of these factors. The intraparticle porosity of seed treatment dust particles varied from 0.02 to 0.51 according to the crop and generally increased with particle size. Calculated settling velocities demonstrated that accounting for particle shape and porosity is important in drift studies. For example, the settling velocity of dust particles with an equivalent diameter of 200 μm may vary between 0.1 and 1.2 m s(-1), depending on their shape and density. Our analysis shows that in a wind velocity of 5 m s(-1), such particles ejected at 1 m height may travel between 4 and 50 m from the source before settling. Although micro-CT is a valuable tool to characterize dust particles, the current image processing methodology limits the number of particles that can be analyzed.
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