Aerodynamic diameter of conidia of Alternaria species

The aerodynamic diameters of conidia of five species of Alternaria and Stemphylium botryosum were estimated using an inertial impaction method based on a May Ultimate Impactor. The same technique was used to estimate the aerodynamic diameter of unidentified Alternaria species collected from an oilseed rape crop. Aerodynamic diameters tended to increase with spore length or diameter and ranged from about 10 to 40 mum, although spore length ranged from about 10 to 220 mum. It was also found that the aerodynamic diameter, and therefore the fall speed of Alternaria-like spores, can be estimated from cylinders of unit density and the same length and mean diameter of the spores

Evaluation of 'alternative' materials to sulfur and synthetic fungicides for control of grapevine powdery mildew in a warm climate region of Australia

The efficacy of 'alternative' materials against powdery mildew (Erysiphe necator) was evaluated on Vitis vinifera cvs Chardonnay and Cabernet Sauvignon in a warm climate region of New South Wales, Australia. In the first season, sulfur, milk, whey, potassium bicarbonate (Ecocarb) and a mixture of potassium bicarbonate and botanical oils (Synertrol Horti Oil) alternated with whey reduced the severity of powdery mildew on Chardonnay bunches at harvest compared with untreated vines, however only sulfur provided commercially acceptable fruit at harvest with a mean disease severity of 4.2%. In the second season, none of the treatments, including sulfur, provided commercially acceptable control of powdery mildew on Chardonnay. The mean severities of powdery mildew on Cabernet Sauvignon were relatively low, with alltreatments providing comparable control to sulfur in the second season. In the third season, spray programs incorporating the 'alternative' materials and sulfur were evaluated on Chardonnay by targeting specific phenological stages of grapevine growth. Programs that included sulfur from bud burst toflowering provided better disease control than those that included a mixture of potassium bicarbonate and botanical oils applied at the same stages. This highlights the importance of effective early season control of this disease on susceptible cultivars such as Chardonnay. Analysis of berry weight, pH, total soluble solids and titratable acidity of juices revealed no negative impact of the treatments. © Australasian Plant Pathology Society Inc. 2010.S. Savocchia, R. Mandel, P. Crisp, E. S. Scot

Pest and disease management: why we shouldn’t go against the grain

Citation: Skelsey, P, . . . & Garrett, K. (2013). Pest and Disease Management: Why We Shouldn't Go against the Grain. PLoS One, 8(9), e75892. https://doi.org/10.1371/journal.pone.0075892Given the wide range of scales and mechanisms by which pest or disease agents disperse, it is unclear whether there might exist a general relationship between scale of host heterogeneity and spatial spread that could be exploited by available management options. In this model-based study, we investigate the interaction between host distributions and the spread of pests and diseases using an array of models that encompass the dispersal and spread of a diverse range of economically important species: a major insect pest of coniferous forests in western North America, the mountain pine beetle (Dendroctonus ponderosae); the bacterium Pseudomonas syringae, one of the most-widespread and best-studied bacterial plant pathogens; the mosquito Culex erraticus, an important vector for many human and animal pathogens, including West Nile Virus; and the oomycete Phytophthora infestans, the causal agent of potato late blight. Our model results reveal an interesting general phenomenon: a unimodal (‘humpbacked’) relationship in the magnitude of infestation (an index of dispersal or population spread) with increasing grain size (i.e., the finest scale of patchiness) in the host distribution. Pest and disease management strategies targeting different aspects of host pattern (e.g., abundance, aggregation, isolation, quality) modified the shape of this relationship, but not the general unimodal form. This is a previously unreported effect that provides insight into the spatial scale at which management interventions are most likely to be successful, which, notably, do not always match the scale corresponding to maximum infestation. Our findings could provide a new basis for explaining historical outbreak events, and have implications for biosecurity and public health preparedness