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Gewasbeschermingsmiddelen worden in de landbouw veel gebruikt om oogstverliezen te voorkomen. Maar tot hoe ver in de wijdere omgeving heeft het gebruik van deze middelen invloed op insectenpopulaties? Daarover is nog weinig bekend, terwijl deze informatie essentieel is voor het inschatten van milieurisico’s en de formulering van beleid.

Cereal-legume intercropping can increase yields, reduce fertilizer input and improve soil quality compared with pure culture. Designing intercropping systems requires the integration of plant species trait selection with choice of crop configuration and management. Crop growth models can facilitate the understanding and prediction of the interactions between plant traits, crop configuration and management. However, currently no existing crop growth model has been calibrated and tested for cereal-legume intercrops throughout Europea. We calibrated the Agricultural Production Systems sIMulator (APSIM) for pure cultures of wheat and faba bean using data from Dutch field trials, and determined the phenological parameters to simulate pure cultures and intercrops from seven field experiments across Europe. APSIM successfully reproduced aboveground dry matters and, for wheat only, grain yields in pure cultures. In intercrops, APSIM systematically overestimated the aboveground dry matter and grain yield of faba bean and underestimated those of wheat. APSIM was reasonably capable of simulating plant heights in pure cultures, but respectively overestimated and underestimated the height of faba bean and wheat in intercrops. In order to simulate wheat-faba bean intercrops better, APSIM should be improved regarding the calculation of biomass partitioning to grains in faba bean and of height growth in both species.

Intercropping is a potential pathway for ecological intensification of high input agriculture. There is, however, a shortage of knowledge about which species combinations and which management for intercropping could be advantageous under western European climate conditions. We therefore conducted a 2 year field experiment in the Netherlands to explore the yield advantages of maize, wheat, pea and faba bean when grown as strip intercrops with conventional management and fertiliser input tailored to species strips. Relative yield total (RYT) of relay strip intercrops with maize was well above one, while RYT of simultaneous intercrops without maize was lower than one. Maize and faba bean dominated in mixtures, with their relative yields exceeding the relative density, while pea had relative yields lower than the relative density. Wheat was overyielding when combined with maize but underyielding when combined with faba bean. The results suggest an important role for complementarity for light capture when crops are managed with sufficient nutrients and water. Under such conditions, intercrops with legumes did not perform better than intercrops without legumes. Faba bean manifested itself as a competitive species that dominated companion species with the same growing period.

Yield gains in intercropping are greatest in systems with maize. We studied functional trait plasticity in maize leaves in intercrops to assess the possible contribution to crop carbon accumulation. We compared leaves at different growth stages and positions on the maize plant in sole crops and intercrops. Responses of maize leaves to shading from faba bean or wheat as companion species resulted in thinner leaves with a lower nitrogen content per unit leaf area and a lower leaf nitrogen concentration. Photosynthesis was reduced in these thinner leaves with lower nitrogen content. The changes in leaf functional traits were especially apparent in border row maize plants. During late maize development, the photosynthetic capacity of maize leaves in intercrops did not recover from earlier competition. The results show that plasticity in leaf functional traits in intercropped maize in response to wheat and faba bean reduces the potential for crop carbon accumulation.

The Tilman model of consumers competing for resources has some aspects that appear counterintuitive. Within the standard Tilman model for a single consumer and a single resource, when a very efficient consumer rapidly eats all available food, the resource density becomes zero, but if there is no food, how can the consumer survive? The paradox can be lifted by realising that on the short term indeed rapid consumption may lead to starvation and a decline in the consumer population, but in the long term a finite resource and consumer density remain. A single consumer living on two essential nutrients leaves the density of the non-limiting nutrient above its critical level, so what is done with the extra food? We explain that this does not imply extra food is consumed, just for fun, but that in fact the food is left untouched because there is no use for it. For a model with two consumers competing for a single nutrient one of the consumers will eventually disappear, even if the food economics of the surviving one is worse and there is still much food wasted. Both are inherent aspects of the model, and the paradox can be avoided if the difference between the consumers is small, in which case it will take very long to reach equilibrium. We argue that in general an extended stability analysis, in which not only the asymptotically stable state is considered, but also the unstable steady states and all time scales involved in the transient dynamics, can help in avoiding apparent contradictions in ecological models, or accepting them

The Panel on Plant Health of EFSA conducted a pest categorisation of 17 viruses of Rubus L. that were previously classified as either non-EU or of undetermined standing in a previous opinion. These infectious agents belong to different genera and are heterogeneous in their biology. Blackberry virus X, blackberry virus Z and wineberry latent virus were not categorised because of lack of information while grapevine red blotch virus was excluded because it does not infect Rubus. All 17 viruses are efficiently transmitted by vegetative propagation, with plants for planting representing the major pathway for entry and spread. For some viruses, additional pathway(s) are Rubus seeds, pollen and/or vector(s). Most of the viruses categorised here infect only one or few plant genera, but some of them have a wide host range, thus extending the possible entry pathways. Cherry rasp leaf virus, raspberry latent virus, raspberry leaf curl virus, strawberry necrotic shock virus, tobacco ringspot virus and tomato ringspot virus meet all the criteria to qualify as potential Union quarantine pests (QPs). With the exception of impact in the EU territory, on which the Panel was unable to conclude, blackberry chlorotic ringspot virus, blackberry leaf mottle-associated virus, blackberry vein banding-associated virus, blackberry virus E, blackberry virus F, blackberry virus S, blackberry virus Y and blackberry yellow vein-associated virus satisfy all the other criteria to be considered as potential QPs. Black raspberry cryptic virus, blackberry calico virus and Rubus canadensis virus 1 do not meet the criterion of having a potential negative impact in the EU. For several viruses, the categorisation is associated with high uncertainties, mainly because of the absence of data on biology, distribution and impact. Since the opinion addresses non-EU viruses, they do not meet the criteria to qualify as potential Union regulated non-quarantine pests.

Trabajo presentado en la 2nd European conference on Xylella fastidiosa (how research can support solutions), celebrada en Ajaccio el 29 y 30 de octubre de 2019., Xylella fastidiosais the causal agent of plant diseases which cause massive economic damage (Almeida, 2016; Chatterjee et al., 2008). In 2013, a strain of X.fastidiosasubsp. paucawas for the first time detected in Italian olives (European Food Safety Authority, 2015; Saponari et al., 2016). Here, we simulate future spread of the bacteria based on climatic suitability modelling and an assumption of radial range expansion. An economic model computes impacts by accounting for discounted foregone profits and losses in investment. The model computes impacts for Italy, Greece and Spain as these countries account for around 95 per cent of the European production (Eurostat, 2016). Climatic suitability modelling indicates that, depending on the suitability threshold, 92.5 to 95.4,88.6 to 89.5 and 85.8 to 98.5 per cent of the national areas of production fall into suitable territory in Italy, Greece and Spain, respectively. Across the elicited rates of radial range expansion (Bragard et al., 2019), the potential economic impact over 50 years rangesfrom 3.58 to 8.69 billion euro if replanting with resistant varieties is not feasible. If replanting is feasible, the impact ranges from 2.00 to 4.13 billion euro. Depending on whether or not replanting is feasible, between 0.67 and 1.64 billion euro can be saved over the course of 50 years if the spread is reduced from 5.18km to 1.1km per year (50% and 5% percentile of elicited spread rate). The analysis highlights the major economic benefits of replanting with resistant olive cultivarsand spread control. This stresses the necessity of strengtheningthe ongoing research on resistance traits and vector control., The present work was presented in the framework of the Joint Annual Meeting of the EU Horizon 2020 Projects POnTE ‘Pest Organisms Threatening Europe' (GA 635646) and XF-ACTORS ‘Xylella fastidiosaActive Containment Through a multidisciplinary-Oriented Research Strategy' (GA727987).