三氯吡氧乙酸对小麦的安全性及生物活性评价

三氯吡氧乙酸属人工合成激素类除草剂,具有用量少、活性高、选择性强等优势。为明确其在小麦田的应用技术,采用整株水平生物法测定了其对10个安徽主栽小麦品种的安全性及对阔叶杂草的生物活性。结果显示,三氯吡氧乙酸对多种阔叶杂草具有较好的活性,在供试剂量288 g(a.i.)·hm^-2时,对荠菜、球序卷耳、大巢菜、宝盖草、葎草、猪殃殃、鳢肠、鬼针草、野老鹳、播娘蒿、牛繁缕、小飞蓬、羊蹄、车前草、青葙活性较好,鲜重抑制率达90.39%~100%;在用量72 g(a.i.)·hm^-2时,对葎草鲜重抑制率达100%,对播娘蒿、荠菜、牛繁缕、球序卷耳、大巢菜、小飞蓬、羊蹄、猪殃殃的活性次之,鲜重抑制率在60.44%~84.30%之间;其对阿拉伯婆婆纳、荠菜、播娘蒿、野老鹳的GR₅₀值分别为97.13、43.03、48.58、54.37 g(a.i.)·hm^-2。安全性结果表明,在用量576 g(a.i.)·hm^-2时,对10个供试小麦品种均较安全,株高抑制率和鲜重抑制率分别在2.98%~13.34%和3.29%~17.47%之间。三氯吡氧乙酸在4种供试小麦烟农999、荃麦725、安农0711、淮麦44和杂草阿拉伯婆婆纳、荠菜、播娘蒿、野老鹳草之间的选择性指数在2.39~12.70之间,表明该药剂在供试小麦与杂草间具有良好的选择性。     

48%盖灌能EC对柑橘黄龙病树伐桩处理试验

在柑橘黄龙病重灾区,病树清理量大,病树伐桩处理困难,目前普遍推行的处理方法费工费时,处理措施难以到位,导致病树伐桩萌芽率高,成为新的传染源。本文利用48%盖灌能EC使用柴油为溶剂对柑橘黄龙病树伐桩进行处理。结果表明,5个处理试验对抑制病树伐桩萌芽均有很好的防效,270 d防效全南县果园达到98.7%,其他都达到100%;同时具有很好的催腐效果。该处理方法操作简单易行,省时省工,可以节省大量的人力和财力,是一种经济、安全、有效的柑橘黄龙病树伐桩处理方法。     

Control of rhododendron (Rhododendron ponticum and R. flavum) in the eastern beech (Fagus orientalis) forests of Turkey

Because purple-flowered rhododendron (Rhododendron ponticum L.) and yellow-flowered rhododendron (R. flavum Don.) significantly reduce seedling growth and regeneration of eastern beech (Fagus orientalis Lipsky) as well as local floristic diversity in northern Turkey, effective and cost-efficient woody control is needed. Various manual (cut and grub) and herbicide (foliar and cut-stump spray) woody control techniques were used in two different beech-rhododendron sites in the Black Sea Region (BSR) of Turkey. Two years later, biological and economic effectiveness were substantially greater with foliar-applied herbicide and grubbing treatments than with the cutting, cut-stump, and check treatments. Yet, grubbing showed a great potential for sprout crown reduction. Cut-stump spray was intermediate in effectiveness. Cutting had the least woody control and economic effectiveness among all of the treatments. Foliar-applied Arsenal SL (imazapyr) had significantly greater rhododendron control than foliar-appliied Garlon 4 (triclopyr ester). Increasing rates did not enhance herbicide efficacy. Reducing rates further may provide the same level of control at less cost.     

Use of propanil and quinclorac tank mixtures for broadleaf weed control on rice (Oryza sativa) levees

Broadleaf weed control on rice levees is an emerging problem faced by growers and consultants in Arkansas, USA. Field experiments were conducted at Lonoke and Stuttgart, Arkansas, in 2007 and 2008 to evaluate the effectiveness of various postemergence herbicides applied alone or in tank mixture with propanil or quinclorac for large-sized broadleaf weed control on rice levees. Rice injury was minimal (≤5%) from all herbicides at 2 weeks after treatment (WAT), and no injury was observed at 4 WAT. Sida spinosa (prickly sida) and Amaranthus palmeri (Palmer amaranth) were the most difficult-to-control weeds on levees. Of the herbicides applied alone, 2,4-D generally supplied the highest and most consistent weed control across the six species evaluated. Quinclorac was generally a better tank-mix partner than propanil for control of the weed spectrum evaluated. Propanil at 4.48 kg/ha lowered the activity of several systemic herbicides on S. spinosa, Polygonum pensylvanicum (Pennsylvania smartweed), and Ipomoea wrightii (palmleaf morningglory). Quinclorac plus 2,4-D was the most consistent tank mixture, providing more than 80% control of all weeds at 2 and 4 WAT, except A. palmeri.     

Influence of herbicides and felling,fertilization, and prescribed fire on longleaf pine establishment and growth through six growing seasons

Recovery of longleaf pine (Pinus palustris P. Mill.) is necessary to arrest the decline of many associated plants and animals, and the establishment of longleaf pine on much of its original range requires artificial regeneration and diligence. In central Louisiana, USA, two fertilization levels (No [NF] or Yes [F-36 kg/ha N and 40 kg/ha P]) in combination with three vegetation treatments (check, two prescribed fires [PF], or multi-year vegetation control by herbicidal and mechanical means [IVM]) were applied to container-grown longleaf pine plantings in two studies. In Study 1 (grass dominated), 6-year-old longleaf pine survival was 52% on the F–checks, 78% on the F–PF plots, and averaged 93% on the other four treatment combinations. Longleaf pine trees on the IVM plots (3.4 m) were significantly taller than on the other two vegetation treatments, and trees on the PF plots (1.8 m) were taller than trees on the check plots (1.2 m). In Study 2 (brush dominated), survival averaged 65% across the six-treatment combinations after 6 years. The longleaf pine trees were 4.7 m tall on the IVM plots and averaged 3.9 m tall on the check and PF plots. Fertilization increased P concentrations in the soil and longleaf pine foliage, while fertilization did not significantly affect longleaf pine height growth. Native fertility was not apparently limiting longleaf pine development contrary to prior research recommendations for these soils. In both studies, the IVM treatment reduced early herbaceous competition and the number and height of arborescent plants. The PF treatment reduced arborescent plant height on the grassy site where fires were more intense than on the brushy site.     

Eight years of seasonal burning and herbicidal brush control influence sapling longleaf pine growth,understory vegetation,and the outcome of an ensuing wildfire

To study how fire or herbicide use influences longleaf pine (Pinus palustris Mill.) overstory and understory vegetation, five treatments were initiated in a 5–6-year-old longleaf pine stand: check, biennial arborescent plant control by directed herbicide application, and biennial burning in March, May, or July. The herbicide or prescribed fire treatments were applied in 1999, 2001, 2003, and 2005. All prescribed fires were intense and averaged 700 kJ/s/m of fire front across all 12 burns. Using pretreatment variables as covariates, longleaf pine survival and volume per hectare were significantly less on the three prescribed fire treatments than on checks. Least-square means in 2006 for survival were 70, 65, 64, 58, and 56% and volume per hectare was 129, 125, 65, 84, and 80 m³/ha on the check, herbicide, March-, May-, and July-burn treatments, respectively. A wildfire in March 2007 disproportionately killed pine trees on the study plots. In October 2007, pine volume per hectare was 85, 111, 68, 98, and 93 m³/ha and survival was 32, 41, 53, 57, and 55% on the check, herbicide, March-, May-, and July-burn treatments, respectively, after dropping trees that died through January 2009 from the database. Understory plant cover was also affected by treatment and the ensuing wildfire. In September 2006, herbaceous plant cover averaged 4% on the two unburned treatments and 42% on the three prescribed fire treatments. Seven months after the wildfire, herbaceous plant cover averaged 42% on the two previously unburned treatments and 50% on the three prescribed fire treatments. Before the wildfire, understory tree cover was significantly greater on checks (15%) than on the other four treatments (1.3%), but understory tree cover was similar across all five treatments 7 months after the wildfire averaging 1.1%. The greater apparent intensity of the wildfire on the previously unburned treatments most likely resulted from a greater accumulation of fuels on the check and herbicide plots that also collectively had a higher caloric content than fuels on the biennially prescribed burned plots. These results showed the destructive force of wildfire to overstory trees in unburned longleaf pine stands while also demonstrating the rejuvenating effects of wildfire within herbaceous plant communities. They caution for careful reintroduction of prescribed fire even if fire was excluded for less than a decade.