Development and evaluation of a warning model for the optimal use of copper in organic viticulture.
Downy mildew caused by Plasmopara viticola is one of the most serious diseases affecting grapevine worldwide, and can significantly affect crop quality and quantity. In organic viticulture, downy mildew control is mainly based on copper compounds, which are toxic to organisms in the soil. For this reason, restrictions concerning the maximum amount of copper that organic growers can apply per hectare have been enacted in several countries. We have developed a warning model and a decision-making procedure to help organic grapevine growers optimize their use of copper against downy mildew. This system is based on treating vines with a variable rate of copper when there is an immediate risk of infection and the vegetation is not sufficiently protected by previous treatments. In 2007, the warning model and the decision-making procedure were tested in two vineyards in northern Italy and compared with the local common practice and an untreated control. The treatment timings and copper application rates recommended by the system resulted in control of downy mildew equivalent to that associated with the common practice, but with a considerable reduction in the total amount of copper applied.
Effect of temperature and wetness duration on infection by Plasmopara viticola and on post-inoculation efficacy of copper
A weather-driven model was developed to predict P. viticola population dynamics on grape leaf surfaces during a discrete wet period. To develop this model, the relationships between temperature, wetness duration, zoospore release, and infection were investigated with environmentally controlled experiments, and equations were developed that fitted the experimental data. Release of P. viticola zoospores from sporangia and infection occurred over a wide range of temperatures, but were highest at 15–20 °C. At these temperatures, zoospore began to be released within 1 h after inoculation, and most infections had already occurred by 3 h after inoculation. β-Gompertz and Weibull equations were used to describe zoospore release and infection, respectively. The post-inoculation efficacy (PIE) of two cooper fungicides was also evaluated. For both fungicides PIE decreased rapidly as application time after inoculation increased, and was < 20 % after 6 h at the optimal temperature for P. viticola development (20 °C). The model proposed here can be used to improve the weather-based models that have been developed for simulating secondary cycles of downy mildew. The model can also be used to predict whether a fungicide application during a discrete infection period will be effective. PIE values for the two copper fungicides were positively correlated with the proportion of P. viticola sporangia on a leaf that had not yet caused infection. Model simulations suggested that the efficacy of a copper treatment increased when these scenarios were less conductive for disease development.
Serum Profiles of Luteinizing Hormone, Oestradiol and Cholesterol and Ovarian Functions in Layer Poultry Birds (Gallus domesticus) Fed Diets Containing Furazolidone
This study was carried out to assess the serum profiles of luteinizing hormone (LH), oestradiol, cholesterol and ovarian functions in layer poultry birds (Rhode Island Red;Gallus domesticus) fed a diet containing various concentrations of furazolidone (FZ). A total of 40 birds were randomly assigned to receive FZ 0, 200, 400 or 800 mg/kg feed (ppm) daily during the pre-laying age, i.e. 13–18 weeks (for 5 weeks). Blood samples were collected at weekly intervals. Concentrations of LH and oestradiol in serum were estimated at alternate weeks using radioimmunoassays. Serum cholesterol levels were analysed by an enzymatic calorimetric method. Furazolidone administration was terminated at the 18th week of age. The birds were sacrificed at 22nd week of age and ovarian tissues were processed for morphometric studies. Serum LH, oestradiol and cholesterol levels were affected by age (p<0.001) and FZ dose (p<0.001). Serum LH and oestradiol levels were lower (p<0.05) in birds receiving FZ 800 mg/kg feed daily compared with the controls, whereas serum cholesterol profiles were lower (p<0.05) in all FZ-administered groups than in the control group. The mean weight of ovaries having no yolky follicles observed in the group receiving FZ 400 or 800 mg/kg feed per day was reduced (p<0.05) compared with the control group. Dosing FZ at 800 mg/kg feed per day reduced (p<0.05) the mean volume of ovaries having no yolky follicles compared with the control group. In birds receiving FZ 800 mg/kg feed per day, the mean length of the oviduct was reduced (p<0.05) as compared with the control group. Morphometric studies revealed that the mean number of oocytes with diameter in the range 401–800 μm decreased (p<0.05) in birds fed FZ 400 or 800 mg/kg feed per day. Initial egg production was affected by age (p<0.001) and dose (p<0.001) of FZ. The mean number of eggs laid by different groups revealed that egg production was reduced (p<0.05) in birds receiving FZ 800 mg/kg feed per day as compared with the controls. The present data suggest that FZ causes suppression in serum profiles of LH, oestradiol, cholesterol and ovarian functions in Rhode Island Red layer poultry birds. Therefore, great care must be taken with use of FZ in layer poultry birds (Gallus domesticus) with regard to dosage and duration of administration.