Pest and disease management system for supporting winter oilseed rape decisions (PASSWORD) - vaildation phase (HGCA Project Report No. 390)

Pests and particularly diseases cause serious loss of yield and quality in winter oilseed rape estimated to exceed £80 million/annum in some years. These losses have occurred despite an annual expenditure of about £3.5 million for insecticides and £12 million on fungicides. Decision-making is difficult because there is complex spatial and temporal variation in pest and disease problems and improved guidance is required. The main objective of this project was to test new disease models developed in the first phase of this project and deliver a decision support system for both pest and disease control in oilseed rape. The regional light leaf spot forecast is well-established and reliable and indicates an increased risk of this disease in spring 2006. A new regional forecast for stem canker incidence preharvest has been developed and made available on the Internet. It was successful in 2004/05 and offers strategic guidance on risk provided weather factors are within the range used to develop the model. A four-stage crop-specific stem canker risk assessment method was developed that predicts the onset of phoma leaf spotting using post-harvest weather data and thermal time relationships for canker development and canker severity. Yield loss can then be calculated from canker severity and the economic impact of stem canker predicted. There is some flexibility in the timing of fungicide sprays to control stem canker. Delays of 2 to 3 weeks beyond a 10-20% plants affected threshold did not adversely affect yield. Stem canker severity and yield of different cultivars showed large variation between years and sites and smaller, but significant, variation in responses to fungicide. When phoma leaf spot appears in late autumn, it is only when plants are small that stem canker is likely to cause yield loss. In commercial crops, there were consistent trends for higher yields to be associated with higher fungicide inputs. Light leaf spot was very difficult to control with fungicides in the Aberdeen area where use of resistant cultivars is essential. The most effective disease control was obtained using a combination of resistant cultivars and fungicides. In some years, responses to fungicides were not cost-effective and targeting their use to high-risk situations is necessary to give the best margins over input costs. Close contact was maintained with potential users during the project and they influenced priorities and design features. The components of PASSWORD decision support system were tested and provide guidance for the management of invertebrate pests, phoma stem canker and light leaf spot. The system will be available to ArableDS for use in autumn 2006

ROTATING-DISK ELECTRODES - THE THEORY OF CHRONOAMPEROMETRY AND ITS USE IN MECHANISTIC INVESTIGATIONS

A general computational strategy is presented for the calculation of the chronoamperometric responses arising from potential-step experiments at rotating disc electrodes. The method is applicable to a wide range of electrode reaction mechanisms and theoretical results are given for single- and double-potential-step experiments for ECE, DISP1, DISP2, EC' and CE reactions. For the last, the treatment is extended to cover the case where reactants have grossly unequal diffusion coefficients. Steady-state behaviour is also deduced. The extent to which the various mechanistic pathways can be distinguished is identified and the necessary experiments defined

Environmental evaluation of alternative chemicals to methyl bromide for fumigation of quarantine pests in transit

The majority of recent quarantine schedules have relied on methyl bromide fumigation. However, due to the phase-out of this fumigant in January 2005 alternative treatments are needed. Four alternative chemical fumigants were tested for their potential to replace methyl bromide as a control agent for Bemisia tabaci , Liriomyza huidobrensis and Frankliniella occidentalis . Phosphine at 2 g/m3 gave promising results at 15 °C with complete mortality of all insects after 24 h exposure. Sulphuryl fluoride, ethyl formate and acetaldehyde caused severe damage to plant foliage after only 4 h exposure. However, sulphuryl fluoride produced 100 % mortality of L. huidobrensis pupae after only 2 h exposure. In a large scale test using phosphine 2 g/m3 at 15 °C complete mortality of L. huidobrensis eggs and pupae was recorded after a 24 h exposure. However, only 98.5 and 86 % mortality of B. tabaci eggs and F. occidentalis eggs, respectively, was recorded after this treatment. Treatments with phosphine produced no significant detrimental effects on subsequent plant growth. The potential of these chemicals to act as alternatives to methyl bromide as quarantine fumigants is discussed

Chemical compatibility testing of the entomopathogenic fungus Lecanicillium muscarium to control Bemisia tabaci in glasshouse environment

The potential for using the entomopathogenic fungus Lecanicillium muscarium to control the sweetpotato whitefly, Bemisia tabaci has been well established in previous studies under both laboratory and glasshouse conditions. In the current study, five chemicals were assessed for their compatibility with L. muscarium for control of B. tabaci under glasshouse conditions. On treatments following the sequential application of chemical product and fungus high mortality of second instar larvae was obtained (the known most susceptible B. tabaci life-stage to fungal infection). Sequential treatment of Savona and Certis spraying oil with L. muscarium produced 95 % and 96 % larval mortality, respectively. Commercially, unacceptable poinsettia foliage damage was recorded seven days post application of Agri-50E. Other plant foliage may prove more tolerant to this product. Incorporation of these chemicals with L. muscarium into integrated control programmes for B. tabaci control in glasshouses is discussed. Further information has been added to the knowledge base for the combined use of chemicals and fungi for the control of B. tabaci

Development of a DSS for diseases and pests in winter oilseed rape

Non peer reviewe