Crop canopy development and structure influence weed suppression

Weed suppression characteristics of different winter cereal species and cultivars were studied in two field experiments in two successive years. Two cultivars each of barley, oats and wheat were studied using the weed Galium aparine L. at a range of densities. Significant differences were found in the suppressive abilities of the crop species: oats being the most suppressive, followed by barley and then wheat. Percentage yield loss was related to G. aparine density using a rectangular hyperbolic model. In 1995–96, significant differences between the two wheat cultivars were found, with cv. Avalon being able to suppress G. aparine growth much more effectively than cv. Spark. However, in 1996–97, high rainfall in May, June and July enabled G. aparine to escape suppression by the cultivars. Cultivar competitive ability was associated with high overall leaf area, resistance to loss of tillers under competitive pressure, greater height, canopy structure and development. The oat cultivars were more competitive at early growth stages than could be accounted for by their canopy structure; the possible contribution of allelopathic exudates to their suppressive ability is discussed.     

Interference between Avena sterilis, Phalaris minor and five barley cultivars

Field experiments were carried out in Northern Greece from 1994 to 1997 to study interference between Avena sterilis L. or Phalaris minor Retz. and five autumn-sown barley cultivars. Weed:crop interference began in early April. Avena sterilis at 120 plants m⁻² showed greater interference against barley than P. minor at 400 plants m⁻². The greatest grain yield and ear number reduction due to interference by either weed was recorded for cvs Klipper and Plaisant, and the least for cv. Athinaida; with cvs Carina and Thermi intermediate. Yield reduction due to A. sterilis for cvs Athinaida, Carina, Thermi, Klipper and Plaisant was 8, 16, 27, 61 and 67%, respectively, while corresponding losses to P. minor were 1, 8, 14, 45 and 55%. These results clearly indicate that growth and consequently yield components of cv. Athinaida were unaffected by the presence of either weed species, while those of cv. Carina were affected by A. sterilis , but not by P. minor . However, dry weight and panicle number of both weed species were severely reduced by interference with cvs Carina, Athinaida and Thermi compared with cvs Klipper and Plaisant. The order of interference of the five barley cultivars tested against A. sterilis and P. minor was Athinaida > Carina > Thermi > Klipper ≥ Plaisant.     

50 g/L 唑啉草酯乳油防除大麦田杂草应用技术

50 g／L唑啉草酯乳油可安全应用于大麦田,有效防除硬草、看麦娘等禾本科杂草。50 g／L唑啉草酯乳油80～120 mL／667 m^2于杂草2～3分蘖期使用,药后90 d对硬草、看麦娘等禾本科杂草的防效仍高达95％以上,显著优于对照药剂50％异丙隆可湿性粉剂150 g／667 m^2处理。     

The competitive interactions between winter barley and Avena sterilis are site-specific

Competition between winter barley and Avena sterilis is expected to depend on the specific conditions present in a given site. Considering that site conditions may be variable within a field, we hypothesised that the lower densities of A. sterilis frequently observed under more favourable soil conditions can be attributed to the improved growth and competitiveness of the barley crop under those conditions. Artificial populations of A. sterilis were established at three sites with different soil properties, both in the absence and the presence of a barley crop. Plant density, total biomass, dry weight per plant, seed production and seed per plant production were measured at different times in two growing seasons. Avena sterilis proved to be a generalist species when growing in monoculture, with similar seed production, regardless of the site conditions. However, when growing with the crop, differences in growth and seed production were observed at the different sites under some climatic conditions. The effect of the crop on A. sterilis biomass and seed production was more pronounced at the sites with finer textures and higher organic matter and nitrogen contents, suggesting that barley site‐specific competitive ability may contribute to limiting weed populations in favourable soils.     

Second World Food Congress

Abstract

Wodlly apple aphid Eriosoma lanigerum (Hsm.) is widely distributed in India. It reproduces all year round on apple and crab apple. Alates are produced from July to November and lay nymphs with degenerate mouth parts. The infestation is spread by nursery plants and air currents. The pest is controlled in the nursery either by dip-treatment with fenitrothion (0.025%) or dichlorvos (0.088%) or by soil application of phorate granules (2.5–3.0 g a.i.) during spring. Subterranean populations can be controlled with granules of dimethoate (15 g a.i.), aldicarb (5.0 g a.i.) or carbofuran (3.0 g a.i.). Aerial populations are controlled by autumn sprays of fenitrothion + dichlorvos + demeton-methyl (0.05%), vamidothion (0.025%), phosophamidon (0.035%) or dimethoate (0.03%). Banding of the trunk base with granules has been found useful in reducing reinfestation by checking the first instar nymphs, which migrate between the aerial and subterranean parts. Resistant root stocks of the ‘M.M.’ series are recommended against the pest.     

紫花苜蓿田春季阔叶杂草除草剂筛选及安全性评价

为明确适用于紫花苜蓿田防除春季阔叶杂草的除草剂,本研究通过室内和田间试验筛选了对紫花苜蓿安全且对春季阔叶杂草防效好的除草剂。室内试验表明,供试的11种除草剂中仅有唑草酮、吡草醚、乙羧氟草醚等3种除草剂对紫花苜蓿具有较好的安全性。通过田间试验发现,40%唑草酮WG 30～66 g/hm²(有效成分用量,下同)和10%乙羧氟草醚ME 75～90 g/hm²处理对春季阔叶杂草具有较好的防治效果,株防效为83.68%～97.32%,鲜重防效为73.18%～95.62%,且对紫花苜蓿有较好的安全性,增产12%以上。综上所述,在紫花苜蓿返青期进行唑草酮和乙羧氟草醚处理可用于紫花苜蓿田春季阔叶杂草防除,具有较好的应用前景。     

磺酰脲类除草剂对禾谷类作物的安全性及药害研究

采用田间小区试验方法,测定了4种磺酰脲类除草剂对玉米、小麦、谷子、高粱4种禾本科作物的安全性。结果表明,4%玉农乐悬浮剂苗后茎叶处理,有效成份推荐量40g/hm²对玉米安全,2倍量80g/hm²对玉米有轻微药害,3倍量120g/hm²对玉米药害严重,植株矮化穗小。推荐量对小麦、谷子、高粱药害严重,苗期死亡;75%宝收干悬浮剂播后苗前土壤处理,有效成分推荐量25g/hm²、2倍量50g/hm²和3倍量75g/hm²对4种作物均安全。苗后茎叶处理,3个剂量对小麦均无明显药害。推荐量对玉米安全,高粱有轻度药害,谷子药害严重,苗期死亡。2倍量玉米有轻度药害,高粱药害严重,部分苗期死亡。3倍量玉米和高粱药害严重,玉米不能恢复正常生长,高粱大部分苗期枯死;25%宝成干悬浮剂苗后茎叶处理,有效成分推荐量18.75g/hm²推荐量对玉米安全,2倍量37.5g/hm²对玉米有轻微药害,7d左右恢复正常生长。推荐量对小麦、谷子、高粱均有药害,2倍量药害严重,苗期死亡;20%豆磺隆可溶性粉剂播后苗前土壤处理,有效成份推荐量15g/hm²下对4种作物均安全,2倍量30g/hm²和3倍量45g/hm²下对玉米、小麦、谷子安全,高粱有轻度药害。苗后茎叶处理,推荐量、2倍量和3倍量对小麦均安全。推荐量对谷子安全,2倍量和3倍量谷子有轻度药害。推荐量下玉米、高粱均有药害,2倍量和3倍量药害严重,不能恢复正常生长。     

50 g/L唑啉草酯乳油对机播大麦田杂草的防除效果及安全性评价

将5％唑啉草酯乳油与50％异丙隆可湿性粉剂进行比较,开展不同剂量小区除草试验.结果表明,5％唑啉草酯乳油900～2 250 mL/hm2剂量对大麦田高密度禾本科杂草防效优异,兼治作用较好,受不利天气影响小,持效期达45d以上,5％唑啉草酯乳油900～1 500 mL/hm2是大麦田的安全使用剂量.     

小麦叶内杀菌剂含量对条锈病组分的定量影响

来源于澳大利亚的２５份麦类作物抗笥材料及中国８个省市的２２个小麦品种对禾谷胞囊线虫太谷群体的抗病性测定表明,６个由硬粒小麦的品种“Ｌａｎｇｄｏｎ”与节节麦的抗性材料为亲本合成的异源六倍体小麦均表现高抗;一些含有抗病基因Ｃｃｎ－１的品种,如Ｆｅｓｔｉｇｕａｙ和Ａｕｓ１０８９４等表现感病;其它来源于澳大利亚的６份燕麦及５份大麦材料也均高抗。     

Influence of liquid manure application method on weed control in spring cereals

Summary Injection of liquid manure (slurry) into the soil is an alternative to the traditional surface application. By the injection method, it is possible to place nutrients closer to the crop sown, thus offering the crop a competitive advantage over weeds. This study compares the response in crop yield, weed density and weed biomass to injection vs. surface application of liquid manure through three growing seasons in barley and oats. The manure applications were combined with treatments of weed harrowing or herbicide spraying or no treatment at all. The levels of weed control and crop yield obtained by harrowing and herbicides were larger when slurry was injected compared with surface application. Without any weed control treatments, the injection method decreased the final weed biomass in barley. The influence of nutrient injection on yield and weed control seemed to be modulated by the time of emergence and the early growth rate of the crop relative to weeds. Thus, because of its early root growth and development, barley responded more quickly to the injection treatment than oats. Consequently, barley became a more competitive crop.     

Mechanical damage to annual weeds and carrots by in-row brush weeding

Field experiments were carried out in order to assess the selectivity of in-row brush weeding in carrots with a natural flora of annual weeds, represented by Urtica urens L., Stellaria media (L.) Vill., Chenopodium album L., Senecio vulgaris L., Capsella bursa-pastoris (L.) Med., Chamomilla suaveolens (L.) Pursh Buch. and Matricaria inodora L. The mechanisms by which the weeds and carrots were controlled (uprooting vs. soil covering) were studied using a portable vacuum-cleaner. Weeds at the two- to four-true-leaf stage proved to be more sensitive to brushing than carrots with two to four true leaves but, for later development stages of the weeds, there were no differences. Weeds at the six- to eight-leaf stage were only killed to an extent of 20–50%. Uprooting generally accounted for 45–90% of the weed mortality at the two- to four-leaf stage, whereas most of the mortality in carrots was the result of soil covering. The vacuum-cleaning method proved to be a simple and rapid way of determining whether plants had been killed by uprooting or soil covering. It was concluded that the major mechanism of weed control obtained by brush weeding is uprooting.