The impact of a fungicide and an insecticide on soybean growth, yield, and profitability

A growing number of soybean producers have begun to incorporate below threshold fungicide and insecticide treatments into their management programs in attempts to increase yield. The objective of this study was to determine the influence of a fungicide and insecticide on soybean yield and growth when disease and insect pressure is minimal. Soybean was planted at three locations across Indiana, USA, in 2009 and 2010 and treated with various combinations of glyphosate, pyraclostrobin, and lambda-cyhalothrin. Yield was increased by 100 kg ha⁻¹ and 150 kg ha⁻¹ by a R4 application of pyraclostrobin alone and by lambda-cyhalothrin alone, respectively. Seed mass was increased 3% by pyraclostrobin, while seed number m⁻² was increased 5% by lambda-cyhalothrin. No other yield component was influenced by the fungicide or insecticide. Economic analysis using Simulation and Econometrics to Analyze Risk (SIMETAR) demonstrated a single, post application of glyphosate to be the most efficient treatment option across a range of risk attitudes. This study indicates that yield increases are possible using below threshold applications of fungicides and insecticides. However, growers may not benefit from such applications if input costs are higher than the economic returns of the increased yield.     

Monitoring resistance of Helicoverpa armigera to different insecticides used in cotton in Spain

Helicoverpa armigera is the key pest of cotton in Spain, resulting in many insecticide treatments against it. The resistance status of H. armigera to different insecticides currently used in cotton was evaluated in Spain in two different seasons, 1999 and 2004. Four populations were tested in total, two in each season. Toxicological bioassays were conducted in the laboratory, and performed on third instar larvae by topical application of the insecticides. LD₅₀'s were estimated by probit analysis and resistance factors (RF) were calculated at the LD₅₀ level. Four insecticides were evaluated, but only endosulfan reached a moderate resistance level (RF = 11.4), and the others (methomyl, chlorpyrifos and lambda-cyhalothrin) showed low resistance (RF between 1.9 and 6.0). Such results indicate the generally low resistance of H. armigera to most of the insecticides used against this pest in cotton in Spain. Possible explanations for this situation are discussed.     

植被过滤带对地表径流中泥沙和杀虫剂的净化效果

通过含沙水流试验,测定了植被过滤带对泥沙、高效氯氟氰菊酯的净化效果。结果表明:入流流量、植被条件是影响植被过滤带拦沙效果的重要因素;高效氯氟氰菊酯的入流浓度越高,植被过滤带断面测定浓度沿程降低越快,当入流浓度分别为0.3、0.6、0.9 mg·L~(-1)时,草地过滤带对高效氯氟氰菊酯的拦截率平均达到61%、71%、75%,灌草地过滤带对高效氯氟氰菊酯的拦截率平均达到52%、69%、74%;入流流量越大,植被过滤带监测断面上的高效氯氟氰菊酯浓度沿程降低越慢,当流量分别为0.87、3.98、7.8 L·s~(-1)时,草地过滤带对高效氯氟氰菊酯的拦截率平均达到61%、50%、33%,灌草地过滤带对高效氯氟氰菊酯的拦截率平均达到52%、44%、40%。研究证实,植被过滤带能有效拦截泥沙、高效氯氟氰菊酯,对农业面源污染具有较好的防治效果。