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Factors affecting the severity of leaf blotch on the two upper leaves of wheat plants in crops at the milky ripe growth stage (GS 73-75) were investigated using survey data from 3513 randomly selected wheat crops sampled during 1985-1996. Year-to-year variation in disease severity was greater than spatial variability at county level, although both showed significant differences. The presence of disease above a 5% severity threshold was modelled using random effects logistic regression (Generalised Linear Mixed Model), which enabled risk variables measured at the field level to be combined with meteorological variables estimated at county level. The final model included terms for the fixed effects of disease resistance rating, date of sowing, high risk septoria periods in May and June, number of fungicide sprays and number of days with frost (£ -2°C) in November. The percentage of crops above the threshold decreased with later sowing, increased number of November frost days and increased number of fungicide sprays. In contrast, high risk septoria periods (rain splash events) in May and June showed a positive correlation with the percentage of crops above the threshold. There were benefits from using resistant cultivars. The model showed that a range of risk variables were of broadly equivalent importance in determining the development of leaf blotch. These risk variables should be integrated in any scheme designed to support fungicide use decisions.

Summary 0[ Pesticides applied to seeds before sowing may present a high risk to seed!eating birds[ Some of these chemicals are highly toxic but are avoided by captive birds in laboratory tests[ However\ evidence for birds avoiding them in the _eld is lacking[ The objective of this study is to investigate avoidance and other factors a}ecting risk of poisoning\ using the model of wood!pigeons Columba palumbus L[ feeding on winter!drilled cereal seed treated with the organophosphorus insecticide fonofos[ 1[ Wood!pigeons feeding on arable _elds in Cambridgeshire\ UK\ were counted once or twice per week over four winters from 0881 to 0885[ In autumn\ newly drilled cereal _elds are shown to be preferred to alternative crops such as stubble and ploughed _elds and root crops[ In spring\ newly drilled cereal _elds are sometimes preferred to older cereal _elds\ stubble\ ploughed _elds and drilled onions[ 2[ Fewer _elds drilled with fonofos!treated cereal seed were used by wood!pigeons than untreated "without fonofos# _elds for the _rst week after drilling only[ The extent of the avoidance reaction was related to the concentration of fonofos on the seed left exposed on _eld surfaces[ 3[ The concentration of fonofos on newly drilled seed exposed on _eld surfaces "mean of 130 mg kg Ð0 # was much lower than expected from the approved application rate "0979 mg kg Ð0 #[ Residues decayed linearly at a rate of 1) per day after drilling and varied widely between _elds[ 4[ The density of seed left exposed after drilling also varied widely between _elds\ being greater on headlands "_eld edges# than the main _eld and declining at a rate of 1) per day after drilling[ 5[ Of 50 wood!pigeons shot within the study area over three winters\ 15 had been feeding on cereal seed and of these\ six contained fonofos residues at levels similar to poisoned birds submitted to the MAFF Wildlife Incident Investigation Scheme[ 6[ In conclusion\ fonofos!treated cereal seed may be partially avoided in the wild[ Avoidance fails to prevent poisoning under some "rare# conditions\ possibly when seed density\ concentrations of fonofos and levels of hunger are all above average[ The implications for risk assessment are discussed[ Key!words] _eld selection\ pesticide residues\ repellency\ risk assessment\ wildlife poisoning[ Journal of Applied Ecology "0888# 25\ 172Ð185

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