Xanthoxylin Found In Secretions Of Epormenis Cestri Feeding On Sebastiania Schottiana Trees Causes Mass Death Of Honeybee Apis Mellifera Larvae

The "River Disease” (RD), a disorder impacting honeybee colonies located closed to waterways with abundant riparian vegetation (including Sebastiania schottiana, Euphorbiaceae), kills newly hatched larvae. Forager bees from RD-affected colonies collect honeydew excretions from Epormenis cestri (Hemiptera: Flatidae), a planthopper feeding on trees of S. schottiana. First-instar honeybee larvae fed with this honeydew died. Thus, we postulated that the nectars of RD-affected colonies had a natural toxin coming from either E. cestri or S. schottiana. An untargeted metabolomics characterization of fresh nectars extracts from colonies with and without RD allowed to pinpoint xanthoxylin as one of the chemicals present in higher amounts in nectar from RD-affected colonies than in nectars from healthy colonies. Besides, xanthoxylin was also found in the aerial parts of S. schottiana and in the honeydew excreted by E. cestri feeding on this tree. A larva feeding assay where xanthoxylin-enriched diets were offered to 1st instar larvae showed that larvae died in the same proportion as larvae did when offered enriched diets with nectars from RD-colonies. These findings demonstrate that a xenobiotic can mimic the RD syndrome in honeybee larvae and provide evidence of an interspecific flow of xanthoxylin among three trophic levels. Further, our results give information that can be considered when implementing measures to control this honeybee disease.

Solving the plastic problem: From cradle to grave, to reincarnation

Plastic packaging accounts for 36% of all plastics made, but amounts to 47% of all plastic waste; 90% of all plastic items are used once and then discarded, which corresponds to around 50% of the total mass of plastics manufactured. Evidence for the ubiquity of microplastic pollution is accumulating rapidly, and wherever such material is sought, it seems to be found. Thus, microplastics have been identified in Arctic ice, the air, food and drinking water, soils, rivers, aquifers, remote maintain regions, glaciers, the oceans and ocean sediments, including waters and deep sea sediments around Antarctica, and within the deepest marine trenches of the Earth. They have also been detected in the bodies of animals, including humans, and as being passed along the hierarchy of food chains, up to marine top predators. Evidence has also been presented that microplastics are able to cross different life stages of mosquito that use different habitats – larva (feeding) to pupa (non-feeding) to adult terrestrial (flying) – and therefore can be spread from aquatic systems by flying insects. The so-called ‘missing plastic problem’ appears to be, in part, due to limitations in sampling methods, that is, many of the very small microplastic particles may simply escape capture in the trawl nets that are typically employed to collect them, but have been evidenced in grab-sampling experiments. Moreover, it is simply not possible to measure entirely through the vast, oceanic volumes of the oceans. It can, however, be concluded with some confidence that the majority of the plastic is not located at the sea surface, and indeed, several different sinks have been proposed for microplastics, including the sea floor and sediments, the ocean column itself, ice sheets, glaciers and soils. The treatment of land with sewage sludge is also thought to make a significant contribution of microplastics to soil. A substantial amount of airborne microparticulate pollution is created by the abrasion of tyres on road surfaces (and other ‘non-exhaust’ sources), meaning that even electric vehicles are not ‘clean’ in this regard, despite their elimination of tailpipe PM2.5 and PM10 emissions. The emergence of nanoplastics in the environment poses a new set of potential threats, although any impacts on human health are not yet known, save, as indicated from model studies. While improved design, manufacture, collection, reuse, repurposing and reprocessing/recycling of plastic items are necessary, overwhelmingly, a curbing in the use of plastic materials in the first place is demanded, particularly from single-use packaging. However, plastic pollution is just one element in the overall matrix of a changing climate (‘the world’s woes’) and must be addressed as part of an integrated consideration of how we use all resources, fossil and otherwise, and the need to change our expectations, goals and lifestyles. In this effort, the role of deglobalisation/relocalisation may prove critical: thus, food and other necessities might be produced more on the local than the global scale, with smaller inputs of fossil fuels for transportation and other purposes, water and fertilisers, along with a marked reduction in the need for plastic packaging.

Olfactory responses and feeding preferences of Copitarsia uncilata (Lepidoptera: Noctuidae) to four aromatic herb specie

Colombian aromatic herbs have great potential as an export commodity. The genus Copitarsia is considered as an economic and a quarantine pest attacking them. In herbivore insects, host plant choice is made by adults and influenced by host plant quality. There were performed olfactory and feeding tests by using four-arm olfactometer and offering four different aromatic herbs (basil, mint, rosemary, or thyme) to determine the host selection behavior of Copitarsia uncilata Burgos and Leiva. Parameters, such as adult choice, larval weight, and time spent by larva on particular herb were measured. The preferences of adults and immature of C. uncilata varied significantly among the herbs in olfactory and larva feeding tests. The adults showed significantly higher responses to essential oils of basil and rosemary. Higher weight of larva was recorded on mint and basil. Further studies on larval development and longevity of adults on different herbs are necessary.

Aphids on cabbage: tritrophic and selective insecticide interactions

Laboratory-based experiments are presented involving two aphid sepcies (Myzus persicae Sulzer, a generalist and Brevicoryne brassicae Linnaeus, a crucifer specialist), and the predatory gall midge, Aphidoletes aphidimyza Rondani, on three cultivars of common cabbage Brassica oleracea var. capitata cv. Derby Day (green-leaved), Minicole (green-leaved) and Ruby Ball (red-leaved). In a laboratory-based tritrophic system including both species of aphid, the three cabbage cultivars and A. aphidimyza, predator both species of aphid, the three feeding on M. persicae or B. brassicae on cv. Derby Day, while growth was slowest separate experiment, A. asphidimyza larva feeding on B. brassicae on each of the three cultivars were significantly smaller and consumed less aphid fresh weight when maintained outdoors (mean temperature = 13.5°C) compared with a constant environment room (20°C). However, in this latter experiment under neither regime were differeneces in predator growth or consumption significant between cultivars. Effects of selective insecticides (pirimicarb and a neem seed kernel extract, NeemAzal-T/SR) on bitrophic (aphid-host plant) interactions were also investigated in the laboratory. A pirimicarb dose equating to c. 15% of the recommended field concentration caused equivalent toxicity of M. persicae on cv. Minicole compared with aphids treated with a three-fold greater dose and reared on cv. Derby Day. Cultivar-mediated differences in aphid mortality caused by the neem extract when tested for systemic and translaminar activity were not apparent. The results are discussed in relation to ways in which host plant selection, selective insecticides and biological control could potentially be manipulated and optimized in aphid management system on brassica crops.

Predicting Encounter Rates for Zooplankton: A Model Assuming a Cylindrical Encounter Field

We delimit a cylindrical attack field for a Chaoborus larva feeding on zooplankton, and propose a mathematical model to predict encounter rates with prey for this ambush predator. The model is based on the encounter process between a stationary cylinder and spheres moving at constant velocity in random directions. The predictions of the model are corroborated in the laboratory.Key words: zooplankton, encounter model, Chaoborus, ambush predator, copepod