Microbial population and diversity on the exoskeletons of four insect species associated with gorse (Ulex europaeus L.)

Fungi and bacteria on the external surfaces of four gorse-associated insect species: gorse seed weevil Apion ulicis Förster (Coleoptera: Apionidae), light brown apple moth Epiphyas postvittana Walker (Lepidoptera: Tortricidae), gorse pod moth Cydia ulicetana Denis and Schiffermüller (Lepidoptera: Tortricidae) and gorse thrips Sericothrips staphylinus Haliday (Thysanoptera: Thripidae), were recov-ered by washing and plating techniques. The isolates were identified by morphology and polymerase chain reaction (PCR) restriction fragment length polymorphism and sequencing of internally tran-scribed spacer (ITS) and 16S rDNA. A culture-independent technique (direct PCR) was also used to assess fungal diversity by direct amplification of ITS sequences from the washings of the insects. All insect species carried Alternaria, Cladosporium, Corallomycetella, Penicillium, Phoma, Pseudozyma spp. and entomopathogens. Ninety-four per cent of the 178 cloned amplicons had ITS sequence similarity to Nectria mauritiicola (syn. Corallomycetella repens).E. postvittana carried the largest fungal spores (spore mean surface area of 126 μm 2) and the most fungal colony forming units per insect. Methylo-bacterium aquaticum and Pseudomonas lutea were isolated from all four insect species. P. fluorescens was the most abundant bacterium on the lepidopteran insects. This study presents the diversity of microbial taxa on insect exoskeletons, and provides the basis for developing a novel mycoherbicide delivery strategy for biological control of gorse using insects as vectors of a plant pathogen

Mechanical and cultural strategies to control Cirsium arvense

Infestation with Cirsium arvense in organic cropping is an increasing problem in many parts of Europe. Non-chemical management strategies against C. arvense based on cultivation tactics and/or different cutting regimes have acquired very little attention for years. This study presents results from four experiments, undertaken under organic growing conditions, on the effects of repeated mowing or hoeing during the first part of the growing season used in combination with competition from a suppressive crop (grass white-clover mixture and red clover). The strategies were mainly aimed at diminishing the regenerative capacity of C. arvense and effects were thus measured in the subsequent year in spring barley. In general, number of passes of mowing and hoeing linearly reduced the amount of aboveground C. arvense biomass in the subsequent year. Increased competition induced by the competitive crops further reduced C. arvense biomass. Differences in barley yield were explained by the amount of C. arvense biomass in the two experiments, while strong confounding effects from Elymus repens infestations occurred in the other two experiments. Our results suggest that the strategies studied are likely to increase crop yield and that an acceptable level of C. arvense control can be achieved within one growing season only