Retention of iprodione on salad onion leaves in relation to the control of Botrytis spp.

Using bioassay and fluorescent tracer techniques it was demonstrated that more fungicide was retained on mature leaves of summer salad onion crops if 1 kg/ha iprodione wettable powder (w.p.) formulation plus wetting agent was sprayed at 280 1/ha than at 560 1/ha or 1120 1/ha.
The lowest spray volume (280 1/ha) with four sprays of iprodione w.p. (0.5 kg in October, November, December and January) gave effective control of Botrytis cinerea and significantly increased plant stand and yield. More fungicide was required to obtain equivalent results using a mixed programme of two thiram (4 kg/ha total) and two iprodione w.p. (2 kg a.i./ha total) sprays at the same application volume and intervals. Where the mixed programme was applied at 1 1 20 1/ha, 1 2 kg a.i. (total fungicide) was necessary to achieve equivalent disease control.
At 280 1/ha, retention and persistence of iprodione on onion foliage was greater with the oil-based than with the wettable powder formulation. In summer especially this resulted in improved Botrytis control and greater numbers of marketable onions. In winter onions, oil and w.p. formulations were equally effective and gave equivalent improvements in plant stand and yield.     

The effect of phenylamide fungicides on the control of potato late-blight (Phytophthora infestans) in England and Wales from 1978 to 1992

During the period 1978–1992, phenylamide fungicides in co-formulation with the dithiocarbamate fungicide mancozeb were tested for the control of potato late-blight in 51 separate field experiments in England and Wales. Whilst there was a general trend over all the experiments which indicated that foliage blight was less severe where the phenylamide + dithiocarbamate mixture had been used, the benefit was more marked in some than in others. Despite the detection of phenylamide resistance, at some sites the mixture gave better control of foliage blight than the dithiocarbamate alone. At one site where continuous data were available, the additional benefit of the phenylamide compound for control of foliage infection was lost after 1986 coinciding with a rise in phenylamide resistance from 31.7% in 1986 to 81% in 1987. Where foliar blight epidemics occurred, yield responses to fungicide programmes compared with unsprayed controls ranged from 0 to +118.5% with a mean response of +30.2%. This is equivalent to 30.8 and 12.92 t/ha respectively. Standardized yield differences were calculated to allow inter-trial and inter-year comparisons and showed no benefit from the phenylamide fungicide applied at 14-day intervals in 33 out of 38 experiments where foliar blight epidemics occurred. At one site, Cusum analysis of standardized yield differences following treatment with the phenylamide + dithiocarbamate mixture and the dithiocarbamate alone showed a mean benefit from the phenylamide mixture of 2.23 t/ha during the period 1978 to 1986. From 1987 to 1992, the yield benefit dropped to a mean level of 0.68 t/ha a decrease of 69.5%. In experiments where blight was not recorded, fungicide treatments had no deleterious effect on yields. Over all the trials, there was no effect of fungicide treatment on the incidence of tuber blight at harvest.     

Plant Diseases

Abstract

Field experiments conducted at Punjab Agricultural University, Ludhiana during 1972–73 and 1973–74 showed that post-emergence application of oxadiazon at 1 kg a.i./ha in transplanted onion gave remarkable weed control and maximum crop yield. Other treatments which performed well include pre-planting alachlor at 2.5 kg a.i./ha plus post-emergence propanil at 1.8 kg a.i./ha and also pre-planting nitrofen at 1.25 kg a.i./ha plus post-emergence nitrofen at 1.25 kg a.i./ha. Herbicides did not significantly influence the bulb quality, soil microflora or the emergence and yield of following crops of okra, bitter gourd and radish.     

Control of loose smut (Ustilago nuda and U. tritici) infections in barley and wheat plants by foliar application of triadimefon

Foliar application of the broad-spectrum systemic fungicide triadimefon to loose smut-infected plants of wheat and barley produced a marked curative effect. Triadimefon was particularly effective when applied at the beginning of and during stem extension. In addition to reducing percentage plant infection, foliar application of this fungicide (particularly prior to flag leaf emergence) resulted in an increased proportion of infected ears which were only partially smutted. The curative effect of these early fungicide applications resulted in significant yield increases, as a consequence of increased grain number per m². Application of triadimefon to crops at ear emergence had no significant effect on percentage plant infection but resulted in lower levels of re-infection following artificial or natural inoculation of healthy ears, apparently as a result of a protectant effect of fungicide residues on or in the ovaries.     

利用播期研究气候条件对黑龙江春玉米产量性状的影响

不同播期致使作物所处的气候条件不同,进而影响作物的生长发育和产量。本文以哲单37(特早熟,生育期113 d)、先玉335(中早熟,118 d)、郑单958(中熟,120 d)等3个玉米品种为试验材料,于2012年到2014年在黑龙江林甸县进行了为期三年分期播种试验,分析了玉米产量相关性状与各个生育阶段气象因子的关系。结果显示:分期播种对3个玉米品种均有影响,其中对早熟品种影响最大。播期主要通过影响玉米百粒重、穗长和秃尖引起产量的变化,贡献最大的因素是百粒重,总效应为0.847,其次是穗长,总效应为0.840,秃尖为负效应,总效应为-0.213。产量性状与气候条件相关性分析发现,玉米产量与抽雄~成熟期的日均温度、降雨呈显著正相关。因此在黑龙江第二积温带播种中早熟和中熟玉米品种(先玉335和郑单958)适当早播可增加抽雄~成熟期的日均温度,增加积温以达到增产的效果;晚播有利于避开早春易发生的干旱、冷害等自然灾害。采用偏最小二乘路径模型PLS-PM处理分析结果显示,播期对产量性状有较大的直接作用(0.763),同时通过影响各生育期的气候和土壤条件间接影响产量。综上所述,在黑龙江西部地区影响玉米产量最关键的气象因子是抽雄~成熟期的温度和降雨,此时适量的灌溉更有利于增加产量。     

EFFECTS OF TIME OF SOWING OF SPRING WHEAT AN D DEFOLIATION OF AGROPYRON REFENS (L.) BEAUV. ON COMPETITION BETWEEN THEM

Summary. Spring wheat, sown at three different times, and Agropyron repens, defoliated at the same three times, were grown separately or together in pots kept in an open-sided cage. The pots were widely spaced and adequately watered. Early sowing of wheat gave a greater grain yield than late sowing, and lessened the loss from competition with Agropyron. Early defoliation of Agropyron slowed its subsequent early growth more than did late defoliation, and plants defoliated early suffered more from competition with wheat. Competition, probably mainly for nitrogen, decreased tillering and the number of ears produced by wheat, more when sowing was late than early, but grain dry weight per ear was decreased equally at the three times of sowing. The rate at which wheat produced leaves was affected by competition only at the last date of sowing. In competition with wheat, Agropyron produced fewer shoots and ears, had lighter shoots and rhizomes, and ear emergence was slightly delayed.     

Studies on the epidemiology and yield losses from rice black-streaked dwarf disease in a recent epidemic in Zhejiang province, China

The spread of rice black-streaked dwarf disease, which has emerged as a major problem on winter wheat and the two summer rice crops (early indica and late japonica ) grown in central and southern Zhejiang province, China, is documented from 1995 to 2007. The late japonica crop suffered the most: up to 64 640 ha were affected with estimated losses of c . 120 000 t grain per year. Peak adult numbers of the small brown planthopper vector, Laodelphax striatellus , coincided with the seedling stages of both rice crops and the proportion of the insect population carrying virus increased during 1998–2005. Seedlings with three to four leaves were the most susceptible, whereas plants inoculated after the end of tillering developed few or no symptoms. Disease levels were strongly correlated with numbers of viruliferous vectors. In sowing-date experiments with both rice crops, the earliest sowings had the most disease and suffered the greatest yield losses. With the last sowing date (25 days after the first), there were almost no losses. There were yield losses of 0·80% for every 1% increase in disease incidence in early indica rice and rather more (0·92%) in the late japonica crop. There were large differences in susceptibility between cultivars, indicating the possibility, within currently available germplasm, of using more resistant cultivars to help contain the disease. Changes in cropping practice and in recent winter weather conditions have probably contributed to the emergence of the virus as a major pathogen in eastern China.     

Predicting light leaf spot (Pyrenopeziza brassicae) risk on winter oilseed rape (Brassica napus) in England and Wales, using survey, weather and crop information

Data from surveys of winter oilseed rape crops in England and Wales in growing seasons with harvests in 1987–99 were used to construct statistical models to predict, in autumn (October), the incidence of light leaf spot caused by Pyrenopeziza brassicae on winter oilseed rape crops the following spring (March/April), at both regional and individual crop scales. Regions (groups of counties) with similar seasonal patterns of incidence (percentage of plants affected) of light leaf spot were defined by using principal coordinates analysis on the survey data. At the regional scale, explanatory variables for the statistical models were regional weather (mean summer temperature and mean monthly winter rainfall) and survey data for regional light leaf spot incidence (percentage of plants with affected pods) in July of the previous season. At the crop scale, further explanatory variables were crop cultivar (light leaf spot resistance rating), sowing date (number of weeks before/after 1 September), autumn fungicide use and light leaf spot incidence in autumn. Risk of severe light leaf spot (> 25% plants affected) in a crop in spring was also predicted, and uncertainty in predictions was assessed. The models were validated using data from spring surveys of winter oilseed rape crops in England and Wales from 2000 to 2003, and reasons for uncertainty in predictions for individual crops are discussed.     

Chemical control of perennial nutsedge (Cyperus rotundus L.) in tropical upland rice

Five herbicides were tested in the dry and in the wet season for their effectiveness in conlrolling perennial nutsedge (Cyperus rotundus L.) in direct-seeded upland rice in the tropics. K-223 [N-(α,α-dimethylbenzyl)-N'-P-tolyl urea] gave the best results. When broadcast sprayed at 8.0 kg a.i./ha in the dry season and 10 kg a.i./ha in the wet season and immediately mixed into the soit just before drilling, K-223 gave excellent perennial nutsedge control with no visible crop damage and increased the grain yield. Bentazone at 2.0 kg a.i./ha applied 7 days after crop emergence was highly selective and gave fair control of nutsedge without being toxic to the crop. MBR 8251 [1.1,1-trifluoro-4′-(phenylsulfonyl) methane-sulfono-o-toluidide] at 2.0 kg a.i./ha, mecoprop (MCPP) at 1.5 kg a.c./ha and fenoprop (silvex) at 1.0 kg a.e./ha applied 7, 14 and 7 days, respectively after crop emergence provided a fair degree of nutsedge control. Fenoprop and MBR 8251 caused slight and mecoprop moderate initial toxicity, but the injury sustained did not significantly affect crop yield.     

Effect of sowing dates and fertilizer on the severity of stem borer (Busseola fusca Fuller,Lepidoptera: Noctuidae) on sorghum in Eritrea

The influence of sowing date and fertilizer application on the incidence anddamage ofthe maize stemborer (Busseolafusca Fuller) in sorghum(Sorghumbicolor L.) was investigated at the Halhale Research Centre in Eritrea during 1997 - 99. The trials were conducted in a splitplot design with sowing date as the main plot and fertilizer as subplots. There were six sowing dates at an interval of 15 days starting fromearly April tomid-June. There were fertilized and unfertilized subplots. Data on larval count, per cent infestation, per cent deadheart, heading and maturity dates, plant height and yield were recorded for each plot. Fertilizer had no effect on the incidence and damage of the stem borer (B. fusca). There was no interaction between fertilizer and sowing dates on the larval population and damage by stem borers. Sowing date had a significant effect on stem borer incidence and damage levels. Early sowing dates (April 1 and 15) had a significantly lower number of larvae, infestation, deadheart and gave higher yields compared with the other sowing dates while late sowing dates (mid-May- mid-June) resulted in significantly higher infestation and damage. The highest infestation and damage were recorded from mid-May sowings. High stem borer infestations in delayed sowing was due to the coincidence of the susceptible stage of the crop (3 - 6 weeks after germination) with high populations ofstemborer larvae fromthe first generationin late June and July. Mid- and late sown crops were also later attacked by the second generation at the grain-filling stage in September- October. These results indicate that early planting (April) is effective in reducing stem borer damage on sorghum in the highlands of Eritrea.     

Chemical Control of Phalaris minor and Avena ludoviciana in Wheat

Abstract

In field experiments conducted at the Punjab Agricultural University, Ludhiana during 1973–74 and 1974–75, pre-emergence application (one day after sowing) of methabenzthiazuron (1.05 kg a.i./ha), metoxuron (1.6 kg a.i./ha) and chlortoluron (0.75 kg a.i./ha) gave effective control of Phalaris minor and Avena ludoviciana in wheat without any phytotoxic effect on the crop. Methabenzthiazuron, metoxuron and chlortoluron gave 1410, 1420 and 1090 kg/ha, respectively, more grain than the unweeded crop and 590, 600 and 270 kg/ha more than the crop hand-weeded twice. Nitrofen (1.25 kg a.i./ha) applied pre-emergence was effective against P. minor only and gave substantial increase in grain yield. Terbutryne, dichlormate and linuron, while effective against P. minor, also had a phytotoxic effect on the crop.     

Fungicide and nitrogen applications in relation to the improvement of disease control and yield in winter barley

In crops of winter barley, cvs Igri and Halcyon, crop structure and intensity of foliar diseases were altered by delaying the main top dressing of nitrogen until mid-April. A single application of fungicide then was sufficient to decrease substantially the severity of fungal disease and improve grain yield at harvest.
Disease control and yield responses were greatest when fungicides were applied during a 3-week period after the main nitrogen application in April. No additional yield benefits were obtained by making two fungicide applications at growth stage (GS) 31 and GS 39.     

Influence de la densité et de la période de concurrence de Solanum nigrum L. sur la tomate de semis direct, en relation avec le désherbage

Effects of density and period of competition by Solanum nigrum L. on direct seeded tomatoes in relation to weed control The effects of density and period of competition from Solanum nigrum L. were measured in direct seeded tomatoes given weed control treatments currently used in south-east France. S. nigrum emerging after a diquat treatment at the 2–3 leaf stage of the crop and thinned to low densities (<12.8 plants ha^?1) at the 5–6 leaf stage of the crop caused significant yield loss if left to compete with the crop until harvest. Yield reduction was smaller if the same weed densities were present only until the onset of flowering. The regression curves of yield on weed density differed as annual climatic variations affected sowing date and plant growth; a comparison between years was made using the relation ‘crop yield × weed biomass/crop biomass’. Significant interactions between weed density and period of competition were found with yield of both green and red fruit. For late sown crops with low densities of S. nigrum two weed control treatments at the 5–6 leaf stage and at the onset of flowering were sufficient to prevent yield loss.     

The effect of controlling Alopecurus myosuroides Huds. and Avena fatua L. individually and together, in mixed infestations on the yield of wheat

Mixed infestations of Alopecurus myosuroides and Arena fatua growing in wheat were controlled individually or together in three experiments. Difenzoquat and ciofop-isohutyl were applied at the early tillering or early stem extension stages of the crops. Early control of both species resulted in significantly higher yields than later control, even though weed emergence was incomplete at the early applications. Herbicides, re-applied at the second date, improved the control of wild-oats hut not of black-grass; yields were not enhanced by this second application Halving the dose of herbicide gave little reduction in weed control or crop yield at the early date, but there was a greater response to dose with the later application. Yields were lower where only one weed was controlled. This work shows the need for broad spectrum control early in the life of the crop to safeguard yield where black-grass, and wild oats occur together in large numbers.     

Deposition and Biological Efficacy of Electrostatically Charged and Uncharged Sprays in Cereal Crops1

Cereal crops were sprayed with conventional hydraulic nozzles (2501/ha), electrostatic hydraulic nozzles (66 l/ha), spinning discs (aqueous 5 l/ha and oil 2 l/ha) and ICI « Electrodyn >> nozzles (1 and 2 l/ha). The ULV sprays were applied with or without air assistance. An experimental triazole fungicide was applied with fluorescent tracer and control of RhynchospoHum secalis in barley and Erysiphe graminis in wheat was compared with deposit data. The two high volume spray systems performed well with no significant differences in disease control or deposition between charged and uncharged modes at 66 l/ha. The spinning disc and « Electrodyn >> systems performed well with air assistance but, without air, deposition was uneven and disease control inferior. The «Electrodyn>> system often produced the largest total deposits but, without air, assistance spray deposition was concentrated mainly in the upper plant parts. The results indicate that under suitable conditions application volumes as low as 1 l/ha can be as effective biologically as high volumes when the same amount of fungicide per hectare is used. Relationships between spray distribution within cereals and sites for pest and disease attack are discussed with regard to different methods of application.     

Effect of Fungicides on Septoria nodorum and Wheat Green Leaf Area1

Fungicides applied at different growth stages were compared for the control of wheat glume blotch, caused by Septoria nodorum (Berk.) Berk. In glasshouse and small-scale field tests, 11 commercially used fungicides, when applied to fully emerged wheat ears, cv. Hobbit, gave only partial control of ear infection by spores applied immediately after spraying. They gave better control of infection of leaves by a similar inoculum. Larger field trials, moreover, indicated better foliar and ear disease control from fungicide applications made before ear emergence, compared with those applied later. In another field trial, nine fungicides were applied to replicated plots of winter wheat, cultivars Atou and Hobbit at GS 31, GS 39, GS 55 or GS 71. On five occasions from anthesis (25 June) until 30 July disease was assessed and green leaf area measured. The trial was harvested on 22 August 1980. Significantly greater yields and grain weights were obtained from plots sprayed with fungicide at GS 39 than from those sprayed at any other time or left unsprayed. Treatments made before symptoms of infection by S. nodorum developed (i.e. before GS 55) prolonged the duration of green leaf areas during the post-anthesis period. Grain weight and yield increases were related closely to the duration of green leaf area above 75 96, but not to the amount of green leaf area at any single assessment nor to the subsequent degree of disease development. The data on which this abstract is based form part of a continuing research programme, the results of which will be published in full at a later date. Full details on the 1980 results referred to above appear in the Annual Report of Long Ashton Research Station (1980).     

The present status of biological control of Xanthium (Compositae)

Abstract

The economic threshold level of the mustard aphid, Lipaphis erysimi (Kaltenbach) was determined on the radish seed crop, var Punjab Sufed. Spraying oxydemeton methyl at 300 g a.i./ ha, was monitored at arbitrary set aphid levels from 25 to 150 aphids/plant. The maximum cost benefit ratio (1: 13.1) was achieved at an aphid level of 50 per plant, requiring three sprays. Spraying in the middle of February was the most crucial, as delay of 7 days from this stage resulted in significant decreases in yield in the fixed spray schedule and at the 75‐aphid level.     

施肥和绿肥翻压方式对旱地冬小麦生长及土壤水分利用的影响

通过田间试验研究渭北旱原不同施肥处理(不施肥;40 kg P2O5/hm2;豆科绿肥专用肥30 kg/hm2)对夏闲期豆科绿肥生长和后茬小麦生长的效果,探讨了夏季豆科绿肥翻压方式(提前翻压、提前覆盖,播前翻压和不种绿肥即夏季休闲)对后茬冬小麦产量及水分利用的影响。研究表明:与不施肥处理相比,豆科绿肥专用肥显著提高绿肥盛花期地上部生物量,但对根系生长没有明显作用;施用磷肥则更有利于绿肥根系生物量的提高;施用绿肥专用肥和磷肥处理的后茬小麦产量较高,特别是绿肥提前翻压时。绿肥提前翻压时冬小麦分蘖数较高、春季总茎数较高、单位面积穗数较高,产量显著高于绿肥提前覆盖、播前翻压和不种绿肥处理,水分生产效率显著高于不种绿肥处理。从绿肥翻压、小麦播前直至小麦拔节期,绿肥翻压方式的3个处理土壤0~200 cm剖面水分含量与休闲处理始终有明显差异。提前翻压处理与提前覆盖、播前翻压处理的差异主要在40 cm以上土层。     

Multiple mid-Atlantic field experiments show no economic benefit to fungicide application when fungal disease is absent in winter wheat

Strobilurin fungicides produce intensified greening and delayed senescence in plants, and have been claimed to enhance yields of field crops in the absence of disease. To help evaluate this claim, available publicly sponsored tests of fungicides on soft red winter wheat in Virginia and North Carolina (n = 42) were analyzed for the period 1994 to 2010. All tests were replicated and had a randomized complete block, split-plot, or split-block design. Each test included 1 to 32 cultivars and one to five fungicides (two strobilurins, one triazole, and two strobilurin-triazole mixtures). There was a total of 311 test-cultivar-fungicide treatment comparisons, where a comparison was the reported yield difference between sprayed and unsprayed treatments of a given cultivar in a given test. Parameters used to calculate the economic benefit or loss associated with fungicide application included a grain price range of $73.49 to 257.21 Mg(-1) ($2 to 7 bu(-1)), a total fungicide application cost of $24.71 to 74.13 ha(-1) ($10 to 30 acre(-1)), and a 0.14 to 0.21 Mg ha(-1) (2.3 to 3.4 bu acre(-1)) loss in yield from driving over wheat during application (with a sprayer 27.4 or 18.3 m [90 or 60 feet] wide, respectively). The yield increase needed to pay for a fungicide application at each combination of cost and price was calculated, and the cumulative probability function for the fungicide yield-response data was modeled. The model was used to predict the probability of achieving a break-even yield, and the probabilities were graphed against each cost-price combination. Tests were categorized as "no-disease" or "diseased" based on reports of the researchers rating the tests. Subsets of the data were analyzed to assess the profitability of the triazole fungicide and the strobilurin-containing fungicides separately in no-disease versus diseased experiments. From the results, it was concluded that, with routine fungicide application based solely on wheat growth stage, total fungicide application costs had to be <$24.71 ha(-1) ($10 acre(-1)) in order to average a ≥ 50% probability of breaking even or making a profit (compared with not spraying). By contrast, if fungicides were applied when fungal disease was present, total application costs of ≤ $47 ha(-1) ($19 acre(-1)) for strobilurins and ≤ $72 ha(-1) ($29 acre(-1)) for propiconazole alone were associated with a ≥ 50% probability of breaking even or making a profit at a wheat price of $184 Mg(-1). The results do not support the application of strobilurin or triazole fungicides to mid-Atlantic wheat crops for "plant health" in the absence of disease. Rather, they support basing the decision to apply fungicide on observation of disease, if an economic return for the input is desired.     

Geographic distribution of false smut disease of rice in India and efficacy of selected fungicides for its management

False smut disease of rice caused by the fungus Ustilaginoidea virens, has become a serious production constraint in various rice-growing regions of India. Analysis of rice false smut disease survey data of last 24 years revealed significant changes in the intensity of the disease in various rice-growing regions of India over the years. We evaluated three fungicide formulations viz., trifloxystrobin-tebuconazole (TT) combination (0.04%), kresoxim methyl (KM) (0.1%) and propiconazole (PC) (0.1%) for their effectiveness against false smut disease of rice. Under in vitro condition, TT and PC completely inhibited the fungal growth while KM inhibited the growth by 80%. We evaluated the efficacy of these chemicals in a multi-location trial in 3 hot spot locations, consecutively for three years. A single fungicide spray was given in 3 different crop stages (booting, 50% panicle emergence and 100% panicle emergence). The results indicated that all the treatments significantly reduced the percentage of both infected panicles and spikelets in all the three locations. Both TT and PC were most effective in reducing the disease intensity and increasing the yield when applied either in booting or in 50% panicle emergence stage.