New approaches in biological control of apple scab

Apple scab caused by Venturia inaequalis is a major disease in apple production. In organic farming scab control depends on the use of fungicides based on copper or sulphur. Since the use of copper will be restricted in the European Union and the use of sulphur often leads to insufficient control and phytotoxicity, alternative control measures are needed. The use of microbial antagonists may be an alternative to fungicides for scab control. Scab epidemics during summer are driven by conidia produced only on apple leaves. In this situation, antagonists present in the phyllosphere may interfere with conidia of the pathogen during sporulation or infection. Within the EU-funded project REPCO, more than hundred fungi were isolated from sporulating scab colonies and tested on apple seedlings for their potential to reduce sporulation of the pathogen. Since the aim of the study was to contribute to the development of a biocontrol product, only candidates were selected which fulfilled a range of additional criteria considering major constraints in development of biocontrol products. The best antagonists were applied under orchard conditions during two growing seasons. The antagonist H39 significantly reduced sporulation of V. inaequalis after most applications. However, in a few cases no effect was found

Selection of antagonists suppressing conidia production of Venturia inaequalis

Novel antagonists for biological control of Venturia inaequalis causing apples scab were screened. Several hundred fungal isolates were obtained from sporulating colonies of V. inaequalis on apple leaves collected at various locations. Candidate antagonists were pre-screened to exclude those isolates with potential risks or low economical feasibility. Remaining isolates were tested on apple seedlings for their ability to reduce conidiation of V. inaequalis. Several promising antagonists could be selected and will be tested under field conditions in summer 2006

Epidemiology of dark leaf spot caused by Alternaria brassicicola in organic seed production of cauliflower

Dark leaf spot caused by Alternaria brassicicola is a seed-borne disease of Brassicae. Production of healthy seed is essential for the organic vegetable production. Literature on the epidemiology of the disease in organic seed production of Brassica was reviewed and an epidemiological field experiments was carried out. External and internal contamination of seeds with A. brassicicola increased steadily during their development. Colonisation of pod tissues as quantified by TaqMan-PCR increased exponentially. The developed knowledge can be used for optimizing cropping systems for organic seed production with lower risks for seed contamination by Alternaria spp. and to develop critical control points for disease management

Conclusions and perspectives: Perspectives for future research-and-development projects on biological

The review of published scientific literature on the biological control of selected pests and diseases has lead to the identification of clear knowledge gaps highlighted in previous chapters. Further bottlenecks were revealed by seeking the possible reasons for the striking discrepancy between the rich inventory of potential biocontrol agents described by scientists and a very small number of commercial products on the market. To complement these analyses, the participants of Research Activity 4.3 of the European Network ENDURE organized consultations of experts (scientists, extension specialists and representatives of the Biocontrol industry) at the occasion of scientific meetings of three Working Groups of IOBC-wpr

Decoherence of a single-ion qubit immersed in a spin-polarized atomic bath

We report on the immersion of a spin-qubit encoded in a single trapped ion into a spin-polarized neutral atom environment, which possesses both continuous (motional) and discrete (spin) degrees of freedom. The environment offers the possibility of a precise microscopic description, which allows us to understand dynamics and decoherence from first principles. We observe the spin dynamics of the qubit and measure the decoherence times (T1 and T2), which are determined by the spin-exchange interaction as well as by an unexpectedly strong spin-nonconserving coupling mechanism

Selection and orchard testing of antagonists suppressing conidia production of the apple scab pathogen Venturia inaequalis

Apple scab caused by Venturia inaequalis is a major disease in apple production. Epidemics in spring are initiated by ascospores produced on overwintering leaves whereas epidemics during summer are driven by conidia produced on apple leaves by biotrophic mycelium. Fungal colonisers of sporulating colonies of V. inaequalis were isolated and their potential to reduce the production of conidia of V. inaequalis was evaluated on apple seedlings under controlled conditions. The four most effective isolates of the 63 screened isolates were tested subsequently under Dutch orchard conditions in 2006. Repeated applications of conidial suspensions of Cladosporium cladosporioides H39 resulted in an average reduction of conidial production by V. inaequalis of approximately 40%. In 2007, applications of conidial suspensions of C. cladosporioides H39 reduced conidial production by V. inaequalis by 69% on August 6 and by 51% on August 16, but no effect was found on August 20. However, viability of available conidia of C. cladosporioides H39 was low at the end of the experiment. Epiphytic and endophytic colonisation by Cladosporium spp. of leaves treated during the experiment with C. cladosporioides H39 was significantly higher than on control leaves sampled 6 weeks after the last application. It is concluded that C. cladosporioides H39 has promising potential as a biological control agent for apple scab control. More information is needed on the effect of C. cladosporioides H39 on apple scab epidemics as well as on mass production, formulation and shelf life of conidia of the antagonist

On the occurrence of polygon-shaped patterns in vibrated cylindrical granular beds

We report experimental observations of polygon-shaped patterns formed in a vertically vibrated bed of circular cross-section. A phase map is determined, showing that the polygon pattern is established for Γ = A(2πf)2/g ≳ 10 . The sensitivity of the polygon structure to bed parameters was tested by studying beds of different particle sizes and fill levels. It was hypothesized that the polygon pattern observed in cylindrical beds is the corresponding pattern to the formation of arches in square-shaped beds. The close relationship between these two patterns was demonstrated by two observations: i) the radii of the arches of a corresponding square bed and the inner radius of the cylindrical bed were found to be very similar and ii) the boundary lengths of the two patterns were in good agreemen