Evaluation of temperature sum models and timing of Quassia amara (Simaroubaceae) wood-chip extract to control apple sawfly (Hoplocampa testudinea Klug) in Sweden.

Apple sawfly (Hoplocampa testudinea Klug) is a serious pest in European organic apple production. They hatch during a short period only, making correct timing of control measures crucial. Swedish organic growers have requested a strategy for optimal timing of the Quassia amara (Simaroubaceae) extract against the apple sawfly. The aim of this study was, therefore, to develop methods to predict the timing of Q. amara control in Sweden. A temperature sum model for timely placement of monitoring or mass-trapping sticky traps was validated for Swedish conditions. The average emergence of sawflies occurred at 169 degree days (SD = 20) counted from March 15 (threshold temperature 4 °C). The difference in emergence from existing first flight model of average and maximum 9 and 39 degree days (1 and 9 calendar days) was found acceptable. Accumulated oviposition of 85 % at full bloom (BBCH 65) suggests that mass trapping and monitoring could stop at this time. This is supported by a tendency of decreased trap catches during that period. Three application times for Q. amara were compared: (A) at petal fall (BBCH 67), (B) at a date calculated using female trap catch numbers and temperature sums, and (C) prior to peak egg hatch observed in the field. All treatments resulted in significantly lower percentage of damaged apples compared to the unsprayed control, with significantly less damage (1.3 %) in plots treated according to method (B). The results provide information on adult phenology and methods that could be used to determine timing of mass trapping and insecticide application against the apple sawfly.

Degradation and leaching of fluroxypyr after application to railway tracks.

Fluroxypyr is an auxin-type herbicide used for postemergent control of broad-leaved weeds in agriculture and in nonagricultural environments such as railways. The overall aim of this study was to assess the potential environmental impact from fluroxypyr application to railway tracks and to elucidate some of the factors that control its environmental fate. In laboratory studies, we examined the degradation of fluroxypyr and the formation of its metabolites fluroxypyr-methoxypyridine (F-MP) and fluroxypyr-pyridinol (F-P) in soil from two Swedish railways. We also investigated the degradation and leaching of fluroxypyr in three different railway plots treated with fluroxypyr (360 g ae ha). The half-life of fluroxypyr in soil samples ranged between 28 and 78 d. An estimated mean 48.6 ± 20% of the fluroxypyr was converted into F-P and 8.0 ± 2% into F-MP. The main metabolite, F-P, was rapidly degraded, with an average half-life of 10 ± 5 d. However, F-MP was not degraded to a significant degree in any sample, resulting in slowly increasing concentrations throughout the experiment. This pattern of relatively rapid degradation of F-P and slow accumulation of F-MP was also observed in the field. The persistent nature of F-MP may be of concern if fluroxypyr is used repeatedly at the same location. Fluroxypyr was detected in the groundwater beneath the track at all three locations studied in concentrations exceeding the EU limit of 0.1 µg L for pesticides in drinking water, and F-P was detected in the groundwater at two of three locations. The most important factor controlling fluroxypyr degradation rate in soil was the soil water content, which modulated microbial activity and presumably also fluroxypyr availability to microorganisms. Our findings imply that fluroxypyr may not be a suitable herbicide for weed control on railway tracks.

Measurements and modeling of pesticide persistence in soil at the catchment scale.

Degradation of pesticides in soils is both spatially variable and also one of the most sensitive factors determining losses to surface water and groundwater. To date, no general guidance is available on suitable approaches for dealing with spatial variation in pesticide degradation in catchment or regional scale modeling applications. The purpose of the study was therefore to study the influence of various soil physical, chemical and microbiological characteristics on pesticide persistence in the contrasting cultivated soils found in a small (13 km(2)) agricultural catchment in Sweden and to develop and test a simple model approach that could support catchment scale modeling. Persistence of bentazone, glyphosate and isoproturon was investigated in laboratory incubation experiments. Degradation rate constants were highly variable with coefficients of variation ranging between 42 and 64% for the three herbicides. Multiple linear regression analysis and Mallows Cp statistic were employed to select the best set of independent parameters accounting for the variation in degradation. Soil pH and the proportion of active microorganisms (r) together explained 69% of the variation in the bentazone degradation rate constant; the Freundlich sorption co-efficient (K(f)) and soil laccase activity together explained 88% of the variation in degradation rate of glyphosate, while soil pH was a significant predictor (p<0.05) for isoproturon persistence. However, correlations between many potential predictor variables made clear interpretations of the statistical analysis difficult. Multiplicative models based on two predictors chosen 'a priori', one accounting for microbial activity (e.g. microbial respiration, laccase activity or the surrogate variable soil organic carbon, SOC) and one accounting for the effects of sorption on bioavailability, showed promise to support predictions of degradation for large-scale modeling applications, explaining up to 50% of the variation in herbicide persistence.

Reaction of foster cows to prevention of suckling from and separation from four calves simultaneously or in two steps.

The aim of this study was to investigate if a 2-step method of preventing suckling and cow-calf separation reduces the stress reaction in foster cows compared with a simultaneous separation method. Seven Swedish Holstein and 5 Swedish Red dairy cows were used as foster cows, each having a group of 4 calves. The foster cow-calf group was formed when calves were 1 wk old, and the calves were prevented from suckling at 10 wk of age. In 6 of the cow-calf groups, calves were prevented from suckling by simultaneous separation from the cow (control). In the other 6 groups, calves were fitted with a nose-flap, which prevented them from suckling while they were kept together with the cow for another 2 wk before they were separated (2-step). The behavior of the foster cows was observed at 4 observation periods, 0 to 2, 8.5 to 9.5, 24 to 26, and 72 to 74 h after the calves were prevented from suckling (2-step), after separation (2-step), and after calves were prevented from suckling by simultaneous separation (control). For both treatments, saliva cortisol was sampled once daily for 5 d at wk 10. This was repeated at wk 12 for the 2-step treatment. Heart rate was measured with the behavioral observations. Control foster cows vocalized more (P < 0.001) and walked more (P = 0.005) than the 2-step foster cows after prevention of suckling and after separation from the calves. When control cows were separated from their calves, they more frequently (P < 0.001) held their head out of the pen than was the case with 2-step cows when separated 2 wk after prevention of suckling. The variation in heart rate was larger in the control group compared with 2-step cows at 0 to 2 h after separation/prevention of suckling (P = 0.002). No effect of treatment was found on cortisol concentration. Our conclusion is that separating the 2 events "prevention of suckling" and "separation" reduces the stress experienced by the foster cow at weaning.

Cadmium levels in kidneys from Swedish pigs in relation to environmental factors--temporal and spatial trends.

The kidney cadmium level in pigs slaughtered at the age of 5-7 months was analysed with respect to geographical and temporal trends. During the period 1984-1992, a total of 1051 samples of porcine kidney from 31 abattoirs were analysed for cadmium at the National Food Administration within the control programme for livestock production. The mean kidney cadmium level was 0.11 +/- 0.07 mg/kg wet wt. (mean +/- S.D.). Regression analysis showed that the cadmium concentration in pig kidney has increased by 2% per year. By using Geographic Information System (GIS), geographical trends in cadmium concentration of porcine kidney were analysed and correlated to cadmium levels in moss and pH in the mor layer of podsolized soil. These two parameters explained 60% of the random variation in cadmium levels in porcine kidney. There were significant differences between individual abattoirs, but no significant longitudinal or latitudinal trend was found. Variation in kidney cadmium levels within breeding stocks was investigated. Kidneys from eight stocks, with five pigs from each, were analysed for cadmium concentration. In spite of the homogeneous treatment of the pig within the same stock, kidney cadmium levels varied on average by a factor of two between individuals. There was a significant correlation between cadmium in feed and cadmium levels in porcine kidney (P = 0.002). The temporal increase in cadmium levels in porcine kidney should be further investigated. An increase in cadmium body burden in pig may be an indicator of an increase in human cadmium exposure.