Phenology and interspecific association of Forficula auricularia and Forficula pubescens in apple orchards

The European earwig Forficula auricularia L. (Dermaptera: Forficulidae) has been widely studied as a key predator of pests in temperate regions, but its phenology and behavior may differ in warmer areas such as the Mediterranean. Here we assessed the phenology, aggregation, and interspecific association of F. auricularia and Forficula pubescens Gené, the only two species found consistently in both ground and canopy shelters in Mediterranean apple orchards. In addition to F. auricularia and F. pubescens, three other earwig species, namely Labidura riparia Pallas, Nala lividipes Dufour and Euborellia moesta Gené, were found occasionally. The mature stages of F. auricularia were observed mainly from May to November in tree shelters and immature ones from October to June in ground shelters. Adult individuals of F. pubescens were observed year-round and nymph instars were detected from April to June in ground as well as in tree shelters. The suitability of the current degree-days models for temperate regions was evaluated for the prediction of European earwig phenology in a Mediterranean climate. Regarding interspecific association, F. auricularia and F. pubescens co-occurred in canopies without apparent competition. This study provides useful weekly data about the phenology of the two earwig species throughout the year that can be used to detect the key periods during which to enhance their populations in pip fruit orchards or to control them in stone fruit crops. Furthermore, our results are of relevance for the development of new phenological models of earwigs in Mediterranean areas where nymphs hibernate, a feature that makes current models inaccurate.Funding: This study was funded by the Spanish project Programa Nacional de Investigación y Desarrollo Agrario nº AGL2010- 17486 (AGR) Control integrado de plagas en frutales de pepita y hueso

The Effect of Low-Haze Diffuse Glass on Greenhouse Tomato and Bell Pepper Production and Light Distribution Properties

Diffuse greenhouse glass can increase the production and growth of several crops, by scattering the incoming direct sunlight, which results in a better and more homogeneous light distribution in the crop canopy. Tomato and bell pepper growers in Belgium tend to install low-haze diffuse glass with a double anti-reflection (AR) coating. These glass types have a limited diffuse effect but have a higher light transmission compared to standard float glass. Therefore, tomato growers often increase stem density to maximize light interception. However, a denser crop could counteract the positive effects of diffuse glass on the vertical light distribution. In this study, the effect of low-haze diffuse glass with an AR coating was evaluated for different cropping densities for tomato and bell pepper taking into account the vertical light distribution throughout the crop canopy. Tomato plants with two stem densities (3.33 and 3.75 stems.m-2) and bell pepper plants (with only one stem density of 7.1 stems.m-2) were evaluated in a greenhouse compartment with diffuse and reference float glass during a full growing season. For tomato, a significant production increase of 7.5% was observed under diffuse glass during the second half of the growing season but only for the low stem density. The benefit of diffuse glass appears most relevant during sunny clear skies and on the sun-side-facing rows of the crop. For bell pepper, no significant production increases were noted between regular float or diffuse glass, because a bell pepper crop is typically covered with thermal screens to prevent sunburn on the fruits during sunny days. The vertical light distribution and the usefulness of AR-coated diffuse glass depends on the crop type and should be optimized accordingly by altering the stem density, leaf pruning strategy, row orientation, or crop variety.status: publishe

Biological control of Fusarium spp. in bell pepper fruit using Gliocladium species

Despite the rising popularity of high quality colored bell peppers, market growth is currently threatened due to internal fruit rot caused mainly by the fungus Fusarium lactis (FLASC), which causes yield losses of 5% with seasonal peaks up to 50%. Although the disease has emerged as a significant threat to bell pepper production, adequate chemical or biological control measures are lacking. Moreover, Belgian pepper production has an overall low impact on the environment with respect to fungicidal use. Therefore, the need for new biocontrol agents (BCA) to tackle internal fruit rot is urgent as bell pepper growers strive to produce low residue fruit. Hence, more than 100 strains of potential antagonistic fungi were screened for mycelial inhibition of FLASC by employment of an adapted dual culture in vitro selection. The main criteria for BCA selection were at least 20% inhibition of mycelial growth after two days of in vitro growth and sporulation quantities exceeding 107 spores mL-1 after one week of growth on potato dextrose medium. After screening, the best candidates were further evaluated in greenhouse trials during three consecutive years. Both screening methods resulted in the selection of two potential isolates of Gliocladium roseum which significantly reduced infections over the three years of field trials. Although these BCAs proved to be effective against internal fruit rot in bell pepper, further screenings should be carried out to investigate safety, environmental risks and ecological characteristics.status: publishe

Rhizogenic agrobacteria in hydroponic crops: epidemics, diagnostics and control

© 2017 British Society for Plant Pathology Rhizogenic Agrobacterium biovar 1, harbouring an Ri-plasmid (root-inducing plasmid), is the causative agent of hairy root disease (HRD) in the hydroponic cultivation of tomato, cucumber and aubergine. The disease is characterized by extensive root proliferation leading to strong vegetative growth and, in severe cases, substantial losses in marketable yield. Agrobacterium biovar 1 is a heterogeneous group of agrobacteria and includes at least 10 genomospecies, among which at least four (G1, G3, G8 and G9) have been associated with HRD in hydroponically grown vegetables. This review has synthesized the current knowledge on rhizogenic Agrobacterium biovar 1, including infection process, current taxonomic status, genetic and phenotypic diversity, detection methods and strategies for disease control. With regard to the latter, symptom reduction and prevention of infection through cultivation methods and chemical disinfection (e.g. by the use of chlorine-based disinfectants and hydrogen peroxide) are discussed and biocontrol strategies are elaborated on. Recent research has led to the identification of a phylogenetically related clade of Paenibacillus strains that have antagonistic activity against rhizogenic Agrobacterium biovar 1 strains, holding great potential for HRD control. Finally, possible directions for future research are proposed.status: accepte