Critical period of weed interference in chickpea

The critical period of weed interference in one variety of chickpea was determined in field experiments carried out at two sites, Tabriz 2002 and Kermanshah 2003, Iran. Chickpea culture was either kept free of weeds for 0, 12, 24, 36, 48 and 60 days after crop emergence (DAE) or weeds were allowed to grow for 0, 12, 24, 36, 48 and 60 DAE. In these experiments, chickpea yield increased with increasing duration of weed-free period and was reduced by increasing duration of weed-infested period. Unweeded conditions for the entire growing season caused 66.4% and 48.3% seed yield reduction when compared with the treatment that was weed-free throughout the growing season, at Tabriz 2002 and Kermanshah 2003, respectively. The results indicated that chickpea must be kept weed-free between the five-leaf and full flowering stages (24–48 DAE) and from the four-leaf to beginning of flowering stages (17–49 DAE) at the two sites, respectively, in order to prevent >10% seed yield loss. At both sites, reduction in seed yield, because of the increased weed interference period, was accompanied by simultaneous reduction in plant dry weight, number of branches, pods per plant and 100-seed weight. This was supported by significant and positive correlations between these traits and chickpea seed yield. There was no significant correlation between the number of seeds per pod and seed yield. A linear regression model was used to describe the relationship between weed dry weight and seed yield loss.     

Potential use of abrasive air-propelled agricultural residues for weed control

A potential new post-emergence physical weed control tactic is described. It entails plant abrasion and death upon assault from abrasive grits propelled by compressed air. Grit derived from granulated walnut shells was delivered by a sand blaster at 517 kPa at distances of 300–600 mm from seedlings of Chenopodium album in glasshouse pots. Control was influenced by size of plants at time of treatment. Seedlings at the cotyledon to 2-leaf stages of growth were mostly destroyed by a single split-second blast of grit of <1 s duration, but were unaltered by compressed air alone. Plants at the 4- to 6-leaf growth stages required up to 10 blasts of grit to be killed. These results indicate that small weed seedlings of susceptible species might be physically controlled by abrasion from air-propelled grit derived from suitable agricultural residues.     

干旱胁迫对藜叶片干旱诱导蛋白的影响

采用SDS-PA GE(十二烷基硫酸钠-聚丙烯酰胺)凝胶电泳法进行蛋白质的分离,研究干旱胁迫对藜叶片干旱诱导蛋白的影响.结果表明:干旱胁迫10 d,中度干旱藜的叶片110.3 KD和103.9 KD及24.8 KD,22.7KD,21.0 KD蛋白谱带明显加强,重度干旱胁迫下22.7 KD,21.0 KD蛋白谱带增强,但弱于中度干旱胁迫;干旱胁迫15 d,中度干旱胁迫下蛋白谱带与第10 d中度干旱胁迫下的蛋白谱带相比,26.4 KD和19.2 KD蛋白谱带增强.这说明干旱诱导了藜一些适应水分胁迫相关基因的表达,或使一些基因的表达量增强,导致一些新蛋白质的出现或某些蛋白质量的增加而增强其对干旱胁迫的抵抗能力.     

Are weed patches stable in location? Application of an explicitly two‐dimensional methodology

Field observations were made in three years continuous maize cultivation in the Netherlands to study the spatial pattern and stability of spatial pattern over time in agricultural weeds. Two‐dimensional correlograms were made, using data from single years, to characterise spatial correlation and pattern, while data from two different years were used to calculate correlation over space and time, to characterise the stability of pattern. Weeds that were able to attain high recruitment also exhibited the strongest spatial correlations. These weeds were Echinochloa crus‐galli, Chenopodium album, Chenopodium polyspermum and Solanum nigrum. Weeds that were less successful in attaining high densities in the maize rotation, also showed less spatial correlation. Wind dispersing Compositae, e.g. Taraxacum officinale, had spatially uncorrelated patterns. All weeds that showed spatial correlation also showed stability in space, except E. crus‐galli. The latter species showed marked population increase and the locations and extent of its patches changed over the years. Statistical interpretation of the data is discussed, as are potential consequences for site‐specific management and optimal sampling of weeds.     

胡萝卜田苗后杂草化学防除药剂筛选

为探究安全、高效的胡萝卜田苗后杂草化学防除技术,采用盆钵法研究了13种苗后茎叶处理除草剂对胡萝卜的室内安全性,并对筛选得到的苗后除草剂进行了初步的田间药效及安全性试验。结果表明：供试13种除草剂中扑草净对胡萝卜的安全性较好,在225 g（a.i.）/hm²剂量下,胡萝卜苗的鲜重为53.61 g,与对照无显著差异,未出现药害反应;在450、750 g（a.i.）/hm²剂量下分别出现了1级和2级的低级别药害反应;而噁草酮、氰草津、嘧啶肟草醚、双草醚、辛酰溴苯腈、乙氧氟草醚、乙羧氟草醚、咪唑乙烟酸、灭草松、噻吩磺隆、双氟磺草胺和氯吡嘧磺隆在推荐剂量下,对胡萝卜鲜重抑制率为19.30%~100.00%,出现了3~5级的药害反应。扑草净对胡萝卜田杂草有较好的防效,在剂量为450~600 g（a.i.）/hm²时对胡萝卜田杂草总体的株防效和鲜重防效均达到80.56%以上,且对胡萝卜安全,无药害反应。胡萝卜田苗后杂草化学防除建议使用450~600 g（a.i.）/hm²扑草净进行茎叶喷雾处理,可达到对禾本科和阔叶杂草的有效防除,且对胡萝卜安全。     

Evaluation of herbicides for selective weed control in grafted watermelons

Grafted watermelon is a combination of two plants, aCucurbita rootstock and a watermelon scion. Therefore, weed control for this crop faces a unique problem: the safety of the selected herbicide has to be tested for both plants that make up the grafted plant. In the current study, we evaluated the usage safety of selected herbicides forCucurbita rootstocks as well as for non-grafted and grafted watermelons, and the control ofAmaranthus retroflexus by the same herbicides. In addition, the residual effect of the herbicides was tested for seeded and transplanted melons representing the next crop following cultivation of the grafted watermelons. The herbicides ethalfluralin, pendimethalin, ethalfluralin, sulfentrazone, oxyfluorfen, chlorsulfuron and clomazone were chosen for their potential to controlA. retroflexus. Pendimethalin and trifluralin were less effective than the other herbicides in controllingA. retroflexus; sulfentrazone, chlorsulfuron and clomazone were not safe for use on the tested cucurbits and thus cannot be recommended for weed control in grafted watermelons. Therefore, by eliminating the herbicides that are toxic to cucurbits and those that are ineffective forA. retroflexus control, it was concluded that the herbicides ethalfluralin and oxyfluorfen can be considered effective and safe for weed control in grafted watermelons. It was shown that trifluralin and oxyfluorfen have the potential to be applied effectively through the drip irrigation system. http://www.phytoparasitica.org posting Jan. 10, 2008.     

亚麻田化学除草剂药效试验报告

用56％2甲4氯钠盐50g／667m^2 5％精喹禾灵乳油50ml/667m^2、17．5％油草双克乳油100ml/667m^2、50％敌草隆可湿性粉剂50g／667m^2 56％2甲4氯钠盐50g／667m^2、50％扑草净可湿性粉剂50g/667m^2 56％2甲4氯钠盐50g／667m^2，对亚麻生长安全，除草效果好。     

新疆鹰嘴豆不同种植密度对其生长发育产量和品质的影响

以阿瓦提1号为材料,研究新疆地区不同种植密度对鹰嘴豆植株性状、干物质积累量、产量与品质的影响。结果表明,随密度的增加,生育期提前,株高增高,叶面积指数上升,单株干物质积累量减少。单株荚数随着密度增大极显著减少。每荚粒数、粒重等与密度的关系不大。蛋白质含量、亚麻酸含量和廿碳烯酸含量都呈现增加的趋势。种植密度对鹰嘴豆维生素B1和油酸含量的影响不显著。在本试验条件下,以44.5万株/hm2处理的表现最佳,产量达5946.09 kg/hm2,品质较好。     

防除玉米田苗后杂草除草剂的选择

玉米田杂草发生种类较多，危害重，本地区常年使用土壤封闭型除草剂在玉米播种后至出苗前喷雾来防除杂草，但因气候、除草剂特性等因素影响，玉米出苗后仍有许多杂草发生，并造成一定的危害。如何在玉米出苗后应用除草剂防除杂草，是需要解决的问题。     

Interaction between glyphosate and various herbicides for broadleaved weed control

The effects of several herbicides for broadleaved weed control on glyphosate (n-phosphonomethyl glycine) phytotoxicity to wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and wild oats (Avena fatua L.) were studied in the greenhouse. In tank mixtures, dicamba (3,6-dichloro-o-anisic acid), 2,4-D (2,4-dichlorophenoxy-acetic acid) and bromoxynil (3,5-dibromo-4-hydroxy benzonitrile) reduced the phytotoxicity of threshold rates of glyphosate on all three species. With increasing rates of the herbicides for broadleaved weed control relative to a fixed rate of glyphosate, there was a general trend towards increased antagonism. Increasing glyphosate rates above the threshold level in mixtures containing a fixed rate of herbicides for broadleaved weed control overcame the antagonism. Both the inert and active ingredients of 2,4-D amine and ester appeared to be involved in the antagonism. There was no reduction in glyphosate phytotoxicity on the annual grasses when 2,4-D or bromoxynil were sprayed sequentially at various times in relation to glyphosate. When droplets of bromoxynil and glyphosate were placed side by side on a leaf, glyphosate phytotoxicity was not reduced, whereas when the two herbicides were mixed and applied as one droplet, considerable reduction in glyphosate phytotoxicity occurred. These results suggest that the reduction in glyphosate phytotoxicity caused by tank mixing with herbicides such as 2,4-D, bromoxynil and dicamba may be due to a physical or chemical incompatability within the tank mixture rather than to a biological interaction in the plant.     

Reduced rates of residual and post-emergence herbicides for weed control in vineyards

In 1997 and 1998, five field studies were conducted at four Portuguese wine‐growing regions in order to evaluate the effectiveness of the chemical control of vineyard weeds under Mediterranean conditions using either reduced doses of residual herbicides or only foliar herbicides. Amitrole (3440 g a.i. ha^?1), amitrole + glyphosate mono‐ammonium salt (1720 + 900 g a.i. ha^?1), amitrole (3400 g a.i. ha^?1), amitrole + diuron (2580 + 1500 g a.i. ha^?1), amitrole + simazine (2580 + 1500 g a.i. ha^?1), amitrole + terbuthylazine (2580 + 1500 g a.i. ha^?1) and amitrole + diuron + simazine (2580 + 1300 + 1400 g a.i. ha^?1) were assayed and compared with the following reference herbicides: glyphosate isopropylamine salt (1800 g a.i. ha^?1), amitrole + diuron (2520 + 1680 g a.i. ha^?1), diuron + glyphosate + terbuthylazine (1275 + 900 + 1425 g a.i. ha^?1), amitrole + simazine (1900 + 3900 g a.i. ha^?1) and glyphosate + simazine (800 + 2200 g a.i. ha^?1). The herbicides were applied during late winter. The results indicated that good control was achieved by the application of foliar herbicides alone or of reduced rates of a mixture of residual herbicides with foliar herbicides for at least 2 months. Three months after application, the efficacy of post‐emergence herbicides and lower rates of residual herbicides decreased significantly in clay soils and under heavy rainfall conditions. Convolvulus arvensis– a weed that is becoming increasingly significant in Portuguese vineyards – was poorly controlled, even when glyphosate was used. Despite this, it can be assumed that in those regions in which the trials were conducted, it is possible to employ weed control strategies that entail the elimination or a reduction in the rate of residual herbicides.     

Weeds for weed control: Asteraceae essential oils as natural herbicides

The aim of this study was to test the botanical family of Asteraceae as a source of natural herbicides. Twenty Asteraceae species were collected during flowering time and evaluated in terms of the yield and quality of essential oils (germination inhibition and growth of weeds). Half the species showed a sufficient yield of essential oil (from about 0.1% to 1.43%) when testing these phytochemicals in vitro as germination inhibitors of two typical weeds, Amaranthus retroflexus and Setaria viridis. Despite the higher tolerance of S. viridis, the concentration of 100 μg L^?1 of essential oils of the two Artemisia species and Xanthium strumarium could totally inhibit germination. In addition, at 10 μg L ^?1, the same essential oils showed full inhibition of A. retroflexus seeds. A comparison of their effectiveness at suboptimal doses led to a further selection of the most promising sources of essential oils. After their chemical characterisation, the essential oils were tested as post‐emergence herbicides on seedlings of the above‐cited weeds. After spraying the weeds at different concentrations (10, 100 and 1000 mg L^?1) during two different phenological stages of weed seedlings (cotyledons and the third true leaf), the essential oils of Artemisia annua and X. strumarium showed the best performance. The essential oils of X. strumarium were then tested again on both weeds to monitor the dynamics of plant injury. A reduction in plant fresh weight (about 20%–30% after 10 days) and chlorophyll content (destroyed, after the same amount of time) was found, thus confirming the total and rapid effectiveness of these essential oils. In summary, A. annua and X. strumarium have elicited considerable agronomic interest and appear to be suitable as a source of essential oils to act as natural herbicides.     

Effects of weed control practices on surface-dwelling arthropod predators in tomato agroecosystems

Weed control, an important practice in agroecosystems to protect crop production, is usually achieved with herbicides. However, these pesticides are expensive, pose potential risks to the environment, may affect some beneficial organisms indirectly, and decrease overall arthropod biodiversity, including pests and their natural enemies, by removing weeds that might act as hosts or shelters for many organisms. The activity density response of important surface-dwelling arthropod predators (ground beetles [Coleoptera: Carabidae], ants [Hymenoptera: Formicidae] and spiders [Arachnida: Araneae]) to herbicides (trifluralin and paraquat), and to two alternative weed management practices (rye straw mulch and mechanical treatment to maintain weeds below threshold levels, in comparison with an untreated check), was assessed using pitfall traps. The mulch treatment had the greatest effect on activity density, reducing the number of predators trapped significantly (P<0.05). Herbicide use resulted in significant (P<0.05) reductions in the activity density of ground beetles. Most predators were trapped in the check plots — which had the highest weed biomass, followed in turn by numbers trapped in the threshold weed control treatment, the full herbicide application and the mulch treatment plots. http://www.phytoparasitica.org posting July 10, 2002.     

密度对全膜双垄沟播不同品种玉米干物质积累及分配的影响

在全膜双垄沟播条件下,研究了不同密度处理2种不同品种玉米富农1号和武科2号干物质积累与分配规律。结果表明:玉米单株干物质积累和群体干物质积累均呈Logistic生长曲线;各生育时期单株干物质积累量随密度增加而减小,群体干物质积累随密度的增加而增加;密度对单株干物质积累的影响主要体现在大喇叭口期以后;密度对干物质分配的影响主要体现在灌浆期以后;茎、叶干物质转移率对密度的反应不敏感,而转换率随密度的增加而上升。     

Characteristics and control of dicamba‐resistant common lambsquarters (Chenopodium album)

The expansion of atrazine‐resistant Chenopodium album (common lambsquarters) since the 1980s has forced New Zealand's maize‐growers to use an additional postemergence herbicide application. The frequent use of dicamba for this has selected for a common lambsquarters population with reduced sensitivity to dicamba. Initial greenhouse experiments with seeds that had been collected from the plants that survived field applications of dicamba showed that these plants could tolerate ≤1.2 kg ha^?1, fourfold the recommended rate. These dicamba‐resistant plants were morphologically distinct from the susceptible population. The leaves of the resistant plants were less dentate and a lighter shade of green. The resistant plants were shorter, had a lower biomass and growth rate and flowered ≤19 days earlier than the susceptible plants. When grown together in various density ratios, the average biomass of both the susceptible and the resistant plants increased as the number of susceptible plants decreased in the mixture. The field experiments demonstrated that the resistant population tolerated dicamba at ≤2.4 kg ha^?1, eightfold the recommended rate. Postemergence applications of bromoxynil, pyridate, nicosulfuron and mesotrione effectively controlled both populations. Nicosulfuron and mesotrione provided long‐term residual control, with nicosulfuron being more effective on the grass weeds. High rates of dicamba damaged the maize plants, resulting in an increased weed cover and reduced grain yield. The number of viable common lambsquarters seeds in the soil seed bank at the end of the growing season declined in the treatments in which common lambsquarters was controlled effectively.     

Potential use of ground‐based sensor technologies for weed detection

Site‐specific weed management is the part of precision agriculture (PA) that tries to effectively control weed infestations with the least economical and environmental burdens. This can be achieved with the aid of ground‐based or near‐range sensors in combination with decision rules and precise application technologies. Near‐range sensor technologies, developed for mounting on a vehicle, have been emerging for PA applications during the last three decades. These technologies focus on identifying plants and measuring their physiological status with the aid of their spectral and morphological characteristics. Cameras, spectrometers, fluorometers and distance sensors are the most prominent sensors for PA applications. The objective of this article is to describe‐ground based sensors that have the potential to be used for weed detection and measurement of weed infestation level. An overview of current sensor systems is presented, describing their concepts, results that have been achieved, already utilized commercial systems and problems that persist. A perspective for the development of these sensors is given. © 2013 Society of Chemical Industry