我国玉米病虫害发生现状、趋势与防控对策

近年来,随着我国农业种植结构的调整和耕作栽培方式的转变,玉米品种选育加快,种植面积迅速增加,玉米病虫害发生一直呈加重趋势,一些次要病虫害在全国范围或局部地区为害不断加重,上升为主要病虫害,生产上还出现了一些新发病虫害,对玉米安全生产构成了威胁。本文总结了我国玉米重要病虫害的发生现状,并对发生趋势进行了分析,目前生产上的重要病虫害如亚洲玉米螟、桃蛀螟、棉铃虫以及黏虫为害加重并将持续发生;土传病害玉米茎腐病、穗腐病等危害将持续加重;风险性叶斑病玉米大斑病、南方锈病等仍在流行,未来不可忽视;还需关注未来危害性具有上升趋势的病虫害。提出了相应的防控对策。     

秸秆全量还田对农作物病虫害的影响及防空对策

在秸秆还田等新的栽培制度下,农作物病虫害的发生规律也产生了新的变化.土传、种传病害的发生呈逐年加重的趋势,多种病虫叠加为害,给农作物的生产安全带来很大的威胁.针对此种情况,提出了靠前防治、压前控后、科学防治、多措并举的防治对策.     

秸秆全量还田对农作物病虫害的影响及防控对策

在秸秆还田等新的栽培制度下,农作物病虫害的发生规律也产生了新的变化。土传、种传病害的发生呈逐年加重的趋势,多种病虫叠加为害,给农作物的生产安全带来很大的威胁。针对此种情况,提出了靠前防治、压前控后、科学防治、多措并举的防治对策。     

山药病害最新研究进展

山药是一种颇具食用和药用保健价值的蔬菜作物,深受广大群众的喜爱,大有发展前途。近年来,随着山药种植面积的不断扩大,其病害发生也随之加重,其中包括真菌病害、细菌病害以及病毒病害等,而这些病害的发生在雨水多的季节尤为突出,其为害程度也随之加重,严重制约着山药的发展。通过对山药病害发生种类、为害症状、病原、病害发生流行规律及防治方法等方面对山药病害进行综述,指出了山药病害研究中存在的问题和未来的研究方向,以期为山药病害进一步研究提供参考依据。     

山药病害最新研究进展

山药是一种颇具食用和药用保健价值的蔬菜作物,深受广大群众的喜爱,大有发展前途。近年来,随着山药种植面积的不断扩大,其病害发生也随之加重,其中包括真菌病害、细菌病害以及病毒病害等,而这些病害的发生在雨水多的季节尤为突出,其为害程度也随之加重,严重制约着山药的发展。通过对山药病害发生种类、为害症状、病原、病害发生流行规律及防治方法等方面对山药病害进行综述,指出了山药病害研究中存在的问题和未来的研究方向,以期为山药病害进一步研究提供参考依据。     

万州红橘褐斑类病害发生规律及综合防治

近年来万州红橘产区出现了一种新型真菌病害——红橘褐斑类病害,发生面积和为害程度呈逐年扩大、加重的趋势,该病不但为害严重且难于控制。通过3年田间发病规律观察、病原菌分离鉴定和防治试验等研究,提出一套红橘褐斑类病害综合防治措施。     

郧西县魔芋常见病害及其防治措施

湖北郧西县的地理位置和气候特点非常适合魔芋栽培,但随着魔芋的大面积种植,其病害也呈逐年加重趋势.分析了魔芋病害的发生种类、为害症状和发生规律,提出了其常见软腐病、叶枯病和白绢病的防治措施,可为郧西县魔芋病害防治提供参考.     

影响烟草野火病发生的关键因子分析

烟草野火病是一种为害多种作物的细菌性病害,国内外均有发生,且有逐年加重为害的趋势。概述影响烟草野火病发生的关键因子,介绍野火病的发病症状、发病规律及流行特征,以有效控制烟草野火病的发生为害。     

信阳油菜立枯病发生规律和防治措施

油菜立枯病又称油菜根腐病,是油菜苗期的主要病害之一。近年来,油菜立枯病在信阳地区呈加重的发生趋势,成为油菜生产上的主要病害之一。介绍油菜立枯病在田间的发病症状、发生规律和为害情况,并采取综合防治措施,以指导油菜立枯病的防治。     

富县苹果褐斑病发生流行规律及其监测预警和综防措施

富县是陕西省确定的首批绿色食品苹果生产基地县,褐斑病是为害该县苹果的主要病害之一,有逐年加重趋势。总结阐述了该病在本县的发生流行规律及其与气候、果园果树种植密度、树龄的关系,分析了该病逐年加重发生流行的原因,提出了对该病的监测预警方法和综合防治措施。     

内蒙古马铃薯干旱等级指标研究

根据马铃薯各生长发育阶段对水分的需求规律,结合内蒙古实际降水供水情况确定了作物水分亏缺指数为表征马铃薯水分亏缺程度的指标.利用内蒙古地区有代表性的26个种植站点1981—2015年的马铃薯产量资料和降水量等气象资料,开展水分亏缺指数和减产率、相对生长高度的相关分析,建立该区域马铃薯干旱灾害等级指标,结合中国气象局行业标...     

植物生物刺激素研究进展

植物生物刺激素是指一类用于促进植物生长发育,缓解非生物胁迫及提高作物品质的物质或微生物,主要包括腐植酸、几丁质及其衍生物、海藻提取物等。生物刺激素的出现,为农产品安全提供了新的思路和解决方法,并广泛应用于农业生产,逐渐成为化肥和农药提质增效的一大利器。本文对生物刺激素定义的发展,主要分类和功能机制,以及生物刺激素在植物营养、生长发育、抵抗非生物胁迫和改善作物品质等方面的研究现状进行了综述,对植物刺激素在农业上的应用前景进行展望,并对存在的问题进行探讨。     

Weed management in organic agriculture: are we addressing the right issues?

Summary Despite the serious threat which weeds offer to organic crop production, relatively little attention has so far been paid to research on weed management in organic agriculture, an issue that is often approached from a reductionist perspective. This paper aims to outline why and how this problem should instead be tackled from a system perspective. Compared with conventional agriculture, in organic agriculture the effects of cultural practices (e.g. fertilization and direct weed control) on crop:weed interactions usually manifest themselves more slowly. It follows that weed management should be tackled in an extended time domain and needs deep integration with the other cultural practices, aiming to optimize the whole cropping system rather than weed control per se . In this respect, cover crop management is an important issue because of its implications for soil, nutrient, pest and weed management. It is stressed that direct (physical) weed control can only be successful where preventive and cultural weed management is applied to reduce weed emergence (e.g. through appropriate choice of crop sequence, tillage, smother/cover crops) and improve crop competitive ability (e.g. through appropriate choice of crop genotype, sowing/planting pattern and fertilization strategy). Two examples of system-oriented weed management systems designed for organic agriculture are illustrated as well as future perspectives and problems.     

Weed competition in a cucumber crop

Abstract

Two field experiments were conducted on cucumber (var. Explorer) during 1979 in a randomised trial design with four replications on the red ferralitic soil of Havana province, Cuba. The effect on the crop of the following different treatments was established: weeded regularly for 20, 30 or 40 days after crop emergence and during the whole crop cycle; left unweeded for these same periods. The mean data of both experiments showed that the weed incidence for 20 or more days following crop emergence affects cucumber yields, causing losses of 100% if the weeds were not removed during the crop cycle. Good high yields, similar to those of the treatment weeded during the crop cycle, were obtained when the weeds were removed 30–40 days after crop emergence.     

Critical periods of weed competition in cotton in Greece

Four experiments were conducted in central Greece during 1997 and 1998 to determine the late-season presence of weeds in cotton (Gossypium hirsutum L.) and the critical times for removing weeds. Experiments were conducted in natural, heavily infested cropland. The presence of weeds for more than 3 weeks after crop emergence caused significant reductions in crop growth and lint yields. However, weeds that emerged 11 weeks or more after crop emergence did not adversely impact yields. Total weed biomass increased with increasing time prior to weed removal. A weed-free period of 11 weeks after crop emergence was needed to prevent significant reductions in cotton height, biomass, number of squares, and yield. These results indicated that postemergence herbicides or other control measures should be initiated within 2 weeks after crop emergence to avoid significant yield reduction. For greater efficiency, soil-applied herbicides in cotton should provide effective weed control for at least 11 weeks. Curvilinear regression equations were derived to describe the relationship between critical periods of weed presence and cotton growth and fruit development.     

Interference of redroot pigweed (Amaranthus retroflexus) in green bean (Phaseolus vulgaris)

Weeds that emerge along with or immediately after crop plants usually can reduce the yield of those crops. Two randomized complete block design experiments were conducted during 2006 and 2007 in Tabriz, Iran to determine the critical period of redroot pigweed control in the green bean hybrid “Cantander”. The treatments were weed‐infested and weed‐free plots at 2, 4, 6, 8, 10, and 14 weeks after bean emergence (WABE). The green bean biomass was affected by the early emergence of redroot pigweed, but it was not reduced when redroot pigweed emerged at 10 weeks after crop emergence, along with crop emergence, and grew with green bean until 4 WABE. The redroot pigweed biomass decreased by 2.7 g m^?2 per day when weed emergence was delayed. Each 100 g m^?2 of weed biomass that was produced resulted in a 1.4 kg ha^?1 loss in the green bean yield. When redroot pigweed interference lasted for ≥4 weeks after green bean emergence, the green bean yield was reduced significantly. Weeds, which emerged 2 weeks after green bean and thereafter were controlled, did not decrease crop productivity significantly. The highest crop yield was obtained when the weed emerged at 14 WABE. The critical period of redroot pigweed control, considering a 10% yield loss, was between 19 and 55 days after green bean emergence. Thus, weed control practises should be begun no later than 3 WABE and should continue until at least 8 WABE in order to obtain the maximum green bean yield.     

Assessment of leaf cover and crop soil cover in weed harrowing research using digital images

Objective assessment of crop soil cover, defined as the percentage of leaf cover that has been buried in soil because of weed harrowing, is crucial to further progress in post‐emergence weed harrowing research. Up to now, crop soil cover has been assessed by visual scores, which are biased and context‐dependent. The aim of this study was to investigate whether digital image analysis is a feasible method to estimate crop soil cover in the early growth stages of cereals. Two main questions were examined: (i) how to capture suitable digital images under field conditions with a standard high‐resolution digital camera and (ii) how to analyse the images with an automated digital image analysis procedure. The importance of light conditions, camera angle, size of recorded area, growth stage and direction of harrowing were investigated, in order to establish a standard for image capture and an automated image analysis procedure based on the excess green colour index was developed. The study shows that the automated digital image analysis procedure provided reliable estimations of leaf cover, defined as the proportion of pixels in digital images determined to be green, which were used to estimate crop soil cover. A standard for image capture is suggested and it is recommended that digital image analysis be used to estimate crop soil cover in future research. The prospects of using digital image analysis in future weed harrowing research are discussed.     

Digitaria sanguinalis seed dormancy release and seedling emergence are affected by crop canopy and stubble

Digitaria sanguinalis is a troublesome annual weed that causes important yield losses in different crops. Despite this, there is scarce information about different aspects of its biology under field conditions. New knowledge about the establishment process of this species will be of paramount importance in order to maximise the effectiveness of weed management. The aims of this paper were to evaluate the effect of stubble found on the surface on seed dormancy levels through the season, the effects of stubble and soyabean crop canopy on seedling emergence and to determine the field emergence pattern as a consequence of seed dormancy level at dispersal time. Seeds on the soil surface, which showed a high dormancy level at the beginning of autumn, were released from dormancy by low winter temperatures and germinated during spring as temperatures rose, showing a transient surface seedbank. Seeds covered by stubbles had delayed the emergence in the field due to lower alternating temperatures perceived by the surface seedbank. On the other hand, the presence of a soyabean crop and stubble together reduced the number of seedlings. Seeds with a high dormancy level at dispersal time showed a delayed emergence in the next season when compared with seeds with a lower dormancy level. However, the final number of seedlings was similar. Both stubble on surface and crop canopy are useful factors to lessen and delay the seedling emergence allowing the design of weed management strategies in order to diminish the population levels of this species.     

Modelling the effects of weeds on crop production

In most quantitative studies on interplant competition, static regression models are used to describe experimental data. However, the generality of these models is limited. More mechanistic models for interplant competition, which simulate growth and production of species in mixtures on the basis of the underlying physiological processes, have been developed in the past decade. Recently, simulation models for competition between species for light and water were improved and a detailed version was developed for sugarbeet and fat hen (Chenopodium album L.). The model was validated with data sets of five field experiments, in which the effect of fat hen on sugarbeet production was analysed. About 98% of the variation in yield loss between the experiments (which ranged from –6 to 96%) could be explained with the model. Further analysis with the model showed that the period between crop and weed emergence was the main factor causing differences in yield loss between the experiments. Sensitivity analysis showed a strong interaction between the effect of the variables weed density and the period between crop and weed emergence on yield reduction. Different quantitative approaches to crop-weed competition are discussed in view of their practical applicability. Simulations of experiments, where both the weed density and the period between crop and weed emergence were varied over a wide range, showed a close relation between relative leaf cover of the weeds shortly after crop emergence and yield loss. This relation indicates that relative leaf cover of the weeds accounts for both the effect of weed density and the period between crop and weed emergence. This relation has the potential to be developed into a powerful tool for weed-control advisory systems.     

耕作方式对夏玉米地杂草关键无草期的影响

在河北省夏玉米地调查了免耕地和常规翻耕地条件下杂草出苗和发生的情况,比较了这两种耕作方式的关键无草期。免耕地杂草出苗较常规耕地略有延后,但很快便趋于一致,两种耕作方式下杂草结束出苗的时间没有区别。耕作方式对夏玉米地关键无草期没有影响,在免耕和翻耕两种耕作方式下,玉米相对产量(RY)和苗后无草期(T)的模型为:RY=98.93×exp[-0.1439×exp(-0.04031×T)],关键无草期均为玉米苗后31d。