1,986 research outputs found
Optimalisation and feasability of bioremediation systems for the processing of spray losses of pesticides
No full textLaboratory evaluation of Bacillus thuringiensis (Vectobac WDG) against mosquito larvae, Culex pipiens and Culiseta longiareolata
No full textC
Entertainer: Pieter-Dirk Uys
No full textThis booklet celebrates the life and work of Pieter-Dirk Uys, internationally acclaimed playwright, author, role-model and one of South Africa's living treasures
Entertainer: Pieter-Dirk Uys
No full textThis booklet celebrates the life and work of Pieter-Dirk Uys, internationally acclaimed playwright, author, role-model and one of South Africa's living treasures
Entertainer: Pieter-Dirk Uys
No full textThis booklet celebrates the life and work of Pieter-Dirk Uys, internationally acclaimed playwright, author, role-model and one of South Africa's living treasures
Mood Regulation as a Design Topic: Interview with Pieter Desmet
No full textPieter Desmet is the founding co-director of the Delft Institute of Positive Design, chair of the TU Delft Department of Human Centered Design, and Director of the Delft Design Labs. After introducing cognitive emotion theory to the field of design research, he established the Design and Emotion Society. Full professor of Design for Experience at TU Delft, Desmet is also co-editor of Design and Emotion Moves (Cambridge Scholars, 2008) and co-author of Positive Design: An Introduction to Design for Subjective Well-Being (IJDesign, 2013). Pieter Desmet, who holds a PhD in the domain of Emotion Psychology, has been recently awarded a five-year personal grant to research about the nuances of human mood in human-product interactions. Besides his academic activities, he also contributes to local community projects, such as a recently developed sensory wellness neighborhood park, and a cultural ‘House of Happiness’ located in Rotterdam. In this interview, Desmet discusses the background to positive design, as well as the practical and ethical challenges that arise from using such an approach. He also refers to his latest research initiative: Design for Mood Regulation. Finally, Desmet explains how he transfers the knowledge he develops to companies
Pesticide risk indicator development for solitary bee species (Osmia spp.)
No full textPesticides are widely used in fruit orchards in Flanders (Belgium). Nonetheless, in the context of Integrated Pest Management (IPM), farmers are advised to restrict the use of pesticides. Alternative strategies to protects crops from pests, diseases and weeds are being used increasingly. However, pesticide residues could still pose a threat to beneficial organisms, such as pollinators. The introductory Chapter 1 takes a closer look at what pesticides are, how risk assessments are conducted on a European level, and the IPM situation in Flemish fruit orchards.
In 2018, at the start of this research, it was not well known which pesticide residues were present in IPM orchards. The environmental characterization of fruit orchards and their contamination, is the subject of Chapter 2. The first main research objective of the doctoral thesis was to elucidate pesticide contamination in fruit orchards. Pesticide concentration in ecologically relevant environmental compartments (topsoil, orchard flora, Osmia-collected pollen and their nesting material) was measured. Non-target organisms (NTOs) with potential pesticide exposure in a fruit orchard are soil-dwelling organisms (for example Arthropoda and Annelida) and wild and managed pollinators (such as solitary bees, bumble bees and honey bees). Therefore, risk assessments were conducted, based on data gathered during the monitoring campaign. Especially pollinators play a crucial role in fruit orchards, both ecologically and economically, precisely because they proved the ecosystem service pollination. The safety of solitary bees raised a lot of concern in Europe. European regulatory testing is still largely performed with the eusocial honey bee (Apis mellifera). However, it is recognized that only one standard test organism in toxicity testing, representing all pollinators, is insufficient. With this in mind, a risk assessment tool was developed for solitary bees: a pesticide risk indicator.
In 2018 and 2019, the aforementioned environmental compartments were sampled in ten sweet cherry (Prunus avium) and eight apple (Malus domestica) orchards. Solitary bee trap nests were provided in each fruit orchard, allowing for continuous pollen sample collection. In these bee trap
nests, solitary bees from the genus Osmia make their nest. In spring, female Osmia spp. collect pollen. They stockpile pollen provisions in the nest, on which they lay an egg, containing a bee larva. A few days later, the larva hatches and start consuming the pollen provision, whereby it develops in about thirty days into a prepupa. The prepupa starts spinning a cocoon and pupation occurs under natural circumstances in September. The adult bee overwinters in a diapausal state (hibernation) in the cocoon, and it is only when temperatures rise (March-April), that the adult bee emerges. The adult bee chews its way through the cocoon and the nesting material, and the life cycle can start all over again.
The second main research objective of the doctoral thesis, was to perform a risk assessment of pesticide residues in topsoil. This was demonstrated in detail in Chapter 3. This chapter might seem a bit odd, because it is not about solitary bees. However, the aboveground-nesting Osmia spp. come into contact with topsoil as well. They use mud to build small walls (hence mason bees) in the nest to separate the different pollen provisions and larvae. It is a challenge to include this kind of exposure in a risk assessment. Above all, there are many more underground-nesting solitary bees. It is evident that these bees are potentially exposed to pesticide residues in topsoil, but it remains difficult to quantify this exposure. Nevertheless, there are bioassays to estimate the terrestrial ecotoxicity in soil. Beneficial organisms such as earthworms are being used for that reason. Hence, it was the aim of this doctoral thesis to take a look at the potential risks for soil-dwelling organisms. Risks for all approved and applied pesticides in fruit orchards were acceptable. However, there were potential unacceptable risks due to persistent residues, coming from historic use. These pesticides had already been banned for more than ten years. This signifies the importance of multi-residue screening in monitoring campaigns, so the current status of banned pesticides in the environment can be assessed as well.
The third main research objective of this doctoral thesis was to validate a toxicity test protocol (bioassay), with two solitary bee species, the European orchard bee (O. cornuta) and the red mason bee (O. bicornis). Full detail of the bioassay is explained in Chapter 4. With this bioassay, it is possible to assess sublethal effects, due to chronic exposure to low concentrations of pesticides. This implies that at low pesticide concentrations, bee larvae do not immediately die, but experience adverse effects, resulting in lower survival chances and a reduced fitness. The larval stage was assumed to be the most vulnerable life stage, because it is the stage where (oral) exposure to pesticide residues is most likely, because larvae consume potentially contaminated pollen. The oral toxicity bioassay for solitary bee larvae was successfully validated in 2021 with as test chemical the neonicotinoid insecticide thiacloprid. The bioassay was immediately put to the test with field-realistic concentrations of six selected insecticides (acetamiprid, methiocarb, pirimicarb, spinosyn A, methoxyfenozide and thiacloprid).
The six aforementioned insecticides were selected, because high toxicity towards solitary bees was presumed. In this bioassay, the 90th percentiles (P90) of measured concentrations were used. The reason for that, is that the specific protection goal for pollinators, as stated by the European Food Safety Authority (EFSA), is exactly this P90 exposure. For the pollination service to be safeguarded, P90 exposure to pesticides should lead to negligible effects (both short term and long term). The bioassay could be seen as an alarm: if adverse effects are observed in a well-controlled laboratory environment, there would likely be a problem in the field as well. During the bioassay, numerous endpoints were observed or measured. The endpoints could be categorized as either acute endpoints, such as larval mortality, or chronic endpoints, such as faster or slower larval development time. Besides these two endpoints, the following endpoints were assessed as well: cocoon mass, pollen consumption, winter mortality, mass loss during overwintering, emergence time and adult longevity.
No adverse effects on both acute and chronic endpoints were recorded, even when the six pesticides were administered in a worst case mixture at the same P90 concentrations. Because no effects (compared to a negative control group) were found, the P90 concentrations are referred to in ecotoxicological terms: No Observed Effect Levels (NOEL). Further testing these insecticides in a dose-response experimental set up (multiple increasing concentrations of the same pesticide) remains necessary in order to refine the obtained NOEL values. From which point onwards (which higher concentration) would the risk be unacceptable?
The fourth main research objective of the doctoral thesis was the development of a pesticide risk indicator for solitary bees. This was illustrated in Chapter 5. One of the constraints of performing a risk assessment for solitary bees, is the lack of toxicological endpoints. There were very few (adult bees) to none (bee larvae) endpoints available in the scientific literature for solitary bees. Although Europe recognizes the importance of solitary bees and bumble bees (Bombus spp.) in regulatory risk assessment of pesticides, thé standard test organism remains the honey bee (Apis mellifera). There is a wide consensus regarding the exposure route variability between bee species and their sensitivity towards pesticides.
A theoretical risk assessment was performed, based on the developed NOEL values for the six selected insecticides. In other words, the newly developed pesticide risk indicator was applied. Briefly, a pesticide risk indicator is a ratio between for example P90 exposure and a Predicted No Effect Level (PNEL). If this ratio is higher than 1, unacceptable risk cannot be excluded. Firstly, exposure is a function of both concentration (µg pesticide per kg pollen) and consumption (kg pollen) (pollen consumption of Osmia spp. was measured as well in this research). Secondly, the derivation of PNEC values (for all solitary bees) from NOEL values (obtained from a bioassay with Osmia spp.) is not straightforward. EFSA assumes that a safety factor of 5 is sufficient to take into account inter-laboratory variability: PNECsolitary bee = NOECOsmia spp./5. By contrast, when honey bee-derived endpoints are used, EFSA recommends an additional safety factor of 10, for taking into consideration the extrapolation from one species to another: PNECsolitary bee = NOEChoney bee/50.
The pesticide risk indicator was used for the risk assessment of the six selected insecticides, and an additional three pesticides, of which honey bee endpoints, were available in literature. These pesticides were the fungicides boscalid and pyrimethanil, approved for use in fruit orchards and also frequently detected in Osmia-collected pollen. The third one was the herbicide linuron, which had an approval for use in fruit cultivation up to 2018. Pesticide residues of linuron were also frequently found in pollen samples. The pesticide risk indicator showed that there was a potential risk due to methiocarb, pirimicarb, thiacloprid and pyrimethanil. For these substances it is highly recommended to perform the larval oral toxicity bioassay for Osmia spp. in a dose-response experimental set-up. This could lead to a less conservative (higher) estimate of the NOEL values. If risks are still unacceptably high, risk assessment should be even more refined, and possibly risk mitigation measures should be put in place.
Finally, a theoretical approach for mixture toxicity risk assessment was showcased. The concept of concentration addition was hereby adopted, a frequently used concept in other domains of ecotoxicological risk assessment. With a method, called the copula method, it was taken into account that pesticide residues do not occur independently in the environment. The combination of these two has never been done, according to the author, in a risk assessment for solitary bees. The theoretical mixture of nine pesticides (of which toxicological endpoints were available) was potentially not safe for solitary bees. The same pesticides as before (as single components) contributed the most to the mixture toxicity. Reason for this: again the probably too conservative estimate of the NOEL values. The only way to refine the risk assessment, is, as was stated before, performing dose-response experiments with the potentially problematic pesticides.
The concluding Chapter 6 concisely provides insight into how all research objectives were met. Of course, answering research questions gives rise to new research questions. Future perspectives are given on how solitary bee risk assessment research should evolve and how this doctoral thesis can be of use
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