Modellierung des Umwelt-Risikopotenzials von Pflanzenschutzstrategien im Zuckerrübenanbau

In frame of an cooperative research project the model SYNOPS to assess environmental risk of plant protection measurements has been successfully applied for evaluation of three chemical plant protection strategies in sugar beet growing tested in field experiments at 9 respectively 10 sites in 2008 and 2009. The assessment has shown relative advantages of the ??Minimal dosage strategy?? with a high number of pesticides against a ??Common practice strategy?? with a smaller number of pesticides and common dose rates and a ??Registered strategy?? with very few pesticides applied with the registered application dose. But all calculated risk indices for earthworms are below the neglect-limit where negative effect can be excluded with high confidence. The same has been found out for water organisms if the pesticide specific application requirements regarding buffer zones are complied with. The results of the field investigations regarding effects on earthworms have confirmed the results of model SYNOPS. Simulation of the tested strategies on all sugar beet fields in 5 large regions in Germany and the comparison with strategies in practice of these regions by means GIS-technology has shown their environmental soundness in general. Only very few calculated risk indices for algae were above the neglect-limit caused by extremely unfavourable application conditions. Whether there is a real risk should be investigated in further hot-spot analysis.     

Effect of Total Water Hardness and Chloride on Survival, Growth, and Feed Conversion of Juvenile Red Drum Sciaenops ocellatus

Juvenile red drum Sciaenops ocellatus were tank-reared in two, separate 30-d trials to assess effects of total water hardness and chloride concentratlon on growth, survival, and feed conversion. Two levels of total hardness and chloride were used in 2 × 2 factorial designs to obtain total hardness and chloride levels in trial one of 100 and 200mg/L CaCO₃ and 125 and 250mg/L Cl⁻, and hardness and chloride levels of 100 and 400mg/L CaCO₃ and 150 and 500mg/L Cl⁻ in trial two. In trial one, average daily growth and feed conversion were significantly ( P ≤ 0.05) improved at 100mg/L hardness levels compared to 200mg/L at both chloride levels. Average daily growth was 0.11 ± 0.02g/d at 100mg/L hardness and 125mg/L Cl⁻ compared to 0.06 ± 0.01g/d at 200 mg/L hardness and 125mg/L chlorides. No significant ( P ≥ 0.05) difference in survival could be attributed to levels of total hardness or chloride. In trial two, 500 mg/L Cl⁻ treatments produced significantly ( P ≤ 0.01) better growth, survival and feed conversion than 150mg/L Cl⁻ at either level of total hardness (100 and 400mg/L). Survival at 150mg/L chloride and 100mg/L hardness was 48.8 ± 18.7%, while at 500mg/L chloride and 400mg/L hardness survival increased to 96.6 ± 2.1%. Growth also increased from 0.14 ± 0.03 to 0.27 ± 0.01g/d and feed conversion improved from 5.77 ± 1.56 to 1.87 ± 0.06 at the same levels. No interactions between levels of hardness or chlorides were shown to affect red drum growth, survival, or feed conversion in either trial.     

Economic and Risk Effects of Rotation Based on a 14-Year Irrigated Potato Production Study in Manitoba

Crop rotations can be used to optimize economic return by preserving or enhancing soil quality and reducing pest pressure. A field experiment consisting of six rotations of potato with canola (P-C), wheat (P-W), canola-wheat (P-C-W), oat-wheat (P-O-W), wheat-canola-wheat (P-W-C-W), and canola underseeded to alfalfa-alfalfa-alfalfa (P-C(A)-A-A) organized in a Randomized Complete Block Design was established on a clay loam soil in Manitoba, Canada and monitored for fourteen years to assess the relative economic performance of potato in each rotation. A stochastic budget based on returns and risk of returns trade-offs was used to determine each rotation’s profitability. While differences in average annual net income of all crops between rotations were not significant, the P-C-W rotation was the most stable. Despite the economic advantage of P-C in the first two cycles, longer P-C-W or P-C(A)-A-A rotations are recommended, as two-year rotations increase plant disease and decrease economic viability in the long run.     

The Effect of Five Stocking Densities on Growth and Yield of Red Swamp Crawfish Procambarus clarkii

A 34-day study was conducted to estimate the effect of stocking density on growth, biomass, and yield of harvestable animals in red swamp crawfish, Procambarus clarkii (Girard). Juvenile crawfish were stocked at l, 2, 4, 8, and 16 crawfish per m² into plastic-lined metal pools planted with rice ( Oryza sativa ) with three replicate pools at each density. Crawfish averaged 35 ± 1.5 mm (SE) total length at the time of stocking.
Growth in total length and weight was significantly affected by density ( P < 0.01), ranging from 91.5 mm and 20.7 g for crawfish stocked at 1 per m² to 62.5 mm and 6.3 g for crawfish stocked at 16 per m². The total crawfish biomass ranged from 20.7 g per m² for crawfish stocked at 1 per m² to 88.7 g per m² at 16 per m². The portion of that biomass made up of harvestable sized animals (>75 mm total length) ranged from 100% at 1 per m² to 0.7% at 16 per m². Gross revenues per ha were projected for crawfish yields at each stocking density with and without a graded product.     

Evaluation of Dual Injection of LHRHa and the Dopamine Receptor Antagonist Pimozide in Cage Spawning of Channel Catfish Ictalurus punctatus

Abstract.— Control of reproduction in cultured fishes has been improved by the use of gonadotropin releasing hormones (GnRH's) and, in many fishes, the use of dopamine (DA) receptor antagonists. However, little successful use of these treatments has been reported for channel catfish Ictalurus punctatus . This study was conducted to investigate the potential of treatment with a gonadotropin hormone releasing hormone (GnRH) and a dopamine (DA) receptor antagonist to improve cage spawning success in channel catfish. Two and 3-yr-old catfish were selected from ponds. All males were injected with des-Gly¹⁰, [D-Ala⁶]-Leuteinizing hormone releasing hormone ethylamide (LHRHa, 50 μg/kg body weight). Females were randomly assigned to the various injection treatments, control (vehicle injected, C), LHRHa only (L), DA receptor antagonist (pimozide) only (P), and LHRHa and pimozide (LP). After injections, one male and one female were paired and placed into 1 m wide × 1.5 m long × 1.2 m deep spawning cages with a metal spawning can. Spawning cans were checked from 1 to 10 d after injection and successful spawning events were recorded. Five trials were conducted between 13 May and 5 June 1998. The LP treatment yielded significantly more spawns than any other treatment (LP, N = 24, 83% > L, N = 25, 44% > C, N = 23, 43 % > P, N = 11, 36%). The greatest promotion of spawning with LP treatment was in the first two induction trials. In the subsequent three trials, differences between treatments were not significant, although LP tre.ated females tended to spawn more frequently. Percent hatch (60.5 ± 3.4%) did not differ between treatments. Treatment of females with LHRHa + pimozide is a potentially useful method for increasing spawning success, particularly early in the spawning season.     

Production Characteristics of Striped Bass × White Bass and Striped Bass × Yellow Bass Hybrids

The potential for commercial culture of hybrid striped bass is promising in many areas of the United States. While several different striped bass hybrids are candidates for culture, differential performance has not been thoroughly evaluated. Comparative performance of two striped bass hybrids was evaluated in six, 757–1, fiberglass tanks receiving a continuous flow of ambient pond water for 397 d. Three replicate tanks were stocked with 50 fingerlings (66 fish/m³) of either striped bass female × white bass male (mean weight 23 g) or striped bass female × yellow bass male hybrids. Fish were fed a 35% protein ration throughout the study, and weight was recorded for all fish at stocking and at 21-d intervals. White bass hybrids grew significantly faster (0.94 g/d) than yellow bass hybrids (0.59 g/d). Survival to harvest averaged 65% and 44% for yellow bass and white bass hybrids, respectively. A significant difference from the expected 1:1 sex ratio occurred for yellow bass hybrids (100% female), but not for white bass hybrids (56% female). Mean condition factor, 1.63 and 1.39, and fillet percentage, 30.7% and 28.4%, was significantly higher for white bass hybrids compared to yellow bass hybrids.