Matching commercial thrips predating phytoseids with the highly diversified climatic conditions of different strawberry production systems

Flower inhabiting thrips (Order: Thysanoptera) are a major threat to fruit quality in strawberry production around the world. As chemical control is often inefficient, alternative control measures are of broad and current interest. Their fast reproduction makes predatory mites highly suitable for thrips control in a crop with a relatively short cropping season like strawberry. However, climatic conditions of strawberry production can differ strongly depending on the production system (glasshouse, plastic tunnel, open field, etc.) and the time span of cultivation (depending mostly on planting date and the type of cultivar: summer-or everbearing). As predatory mites typically display a temperature-dependent life history and the current commercially available thrips predating phytoseids vary in geographic origin, one can assume that under certain climatic conditions some species will be more applicable than others. The goal of this study is to determine which species are suitable for which climatic conditions. Therefore all (Belgian) production systems and time spans are categorized into three climate types, simulated in the laboratory. The population build-up of seven predatory mite species (A. degenerans, A. montdorensis, A. andersoni, A. limonicus, A. swirskii, N. cucumeris and E. gallicus) were assessed for each of these climatic conditions. Under the coldest condition (A), the in West-Europe indigenous E. gallicus was the only species with a significant population build up. When moderate conditions (B) were simulated E. gallicus, N. cucumeris and A. limonicus were most successful. The warmest regime (C) was most adequate for E. gallicus and A. swirskii

Estimated storage of amorphous silica in soils of the circum-Arctic tundra region

We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum-Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil reservoir (0-1 m depth) in circum-Arctic tundra terrain. At all sites, the vertical distribution of ASi concentrations followed the pattern of either (1) declining concentrations with depth (most common) or (2) increasing/maximum concentrations with depth. Our results suggest that a set of processes, including biological control, solifluction and other slope processes, cryoturbation, and formation of inorganic precipitates influence vertical distributions of ASi in permafrost terrain, with the capacity to retain stored ASi on millennial timescales. At the four study sites, areal ASi storage (0-1 m) is generally higher in graminoid tundra compared to wetlands. Our circum-Arctic upscaling estimates, based on both vegetation and soil classification separately, suggest a storage amounting to 219 ± 28 and 274 ± 33 Tmol Si, respectively, of which at least 30% is stored in permafrost. This estimate would account for about 3% of the global soil ASi storage while occupying an equal portion of the global land area. This result does not support the hypothesis that the circum-Arctic tundra soil ASi reservoir contains relatively higher amounts of ASi than other biomes globally as demonstrated for carbon. Nevertheless, climate warming has the potential to significantly alter ASi storage and terrestrial Si cycling in the Arctic

Thrips control with predatory mites A. limonicus and A. swirskii in different strawberry cultivation systems

Western flower thrips or Frankliniella occidentalis is the most common thrips present on strawberry plants and causes damage to strawberries worldwide. F. occidentalis feeds on the cell content of developing flowers and fruits which results in aberrant fruit characteristics: grooves, cat faces, bronzing and prominent seeds. To combat thrips, a wide range of chemical products are used. However, upcoming resistance of thrips to these chemicals causes loss of efficiency. Hence, a new solution to control thrips in strawberries is becoming a high priority. Both the risk for resistance when using chemicals and the urge to lower residues on fruit, increase the interest in natural enemies to control pests. At Research Centre Hoogstraten (PCH), we screened multiple predators for their suitability to control thrips in strawberry. Unique for strawberry cultivation in Belgium and The Netherlands is that it takes place in multiple systems year-round of which the season is relatively short and therefore it is important that predators can survive and establish a sufficient population in these different conditions. At PCH we screened compatible predators for their efficiency to control thrips in the different cultivation systems. This intense search payed off and two predatory mites proved their ability to combat thrips in both individual cages and multiple cultivation systems at PCH and private cultivators. Amblydromalus limonicus is able to control thrips in mild conditions, Amblyseius swirskii prefers warmer temperatures. The predatory mite is scattered over the crop and it will establish itself on the leaves whenever food is available. When thrips levels rise, the predatory mites increase in population and are able to keep thrips at non-damaging levels. A. limonicus and A. swirskii are therefore perfectly suitable to become an important aspect of integrated pest management (IPM) in strawberry so that high quality fruit can be maintained