Developing equations to estimate potato yield loss caused by early blight in Minnesota

Regression analyses were performed on field data from 1981 and 1982 to determine models for estimating yield loss caused by early blight in potato cvs. Norland and Russet Burbank. Percent yield loss (total tubers and US# 1 tubers) caused by early blight could not be satisfactorily explained by any regression model using only a single disease assessment as the input variable. Several multiple point models, which explained more than 70% of the variation in yield loss due to early blight, were determined for each cultivar. The models for cv. Norland used either early blight severity assessments on days 56, 66, 76 and 86 after sprout emergence, or blight severity increments for 10-day periods among days 46–86, as the input variables. The models for cv. Russet Burbank used the same input variables as for cv. Norland and additionally, blight severity on day 96. Yield loss in US#1 tubers was a more stable variable than loss in total tubers for estimating early blight effect.     

Some approaches to prediction of potato early dying disease severity

There are two control procedures available to growers who have fields that may develop severe potato early dying. The first, use of long crop rotation sequence, may result in only marginal control. The second, soil fumigation, is costly; and while providing effective control in many cases, has failed in others. Because of the cost of fumigation and its limited effectiveness in some situations, it may be helpful to predict the potential severity of the disease and subsequent yield loss. One approach to disease and yield loss prediction could be to rely on historical knowledge of early dying severity and yield in a field. Another approach is to use soil inoculum levels as an indicator of potential disease severity and yield loss. Because severity of potato early dying may vary from year to year in a given field as a result of differing environmental conditions, neither historical knowledge nor estimated soil inoculum levels may be sufficient for predicting disease severity. These methods may, however, provide an estimate of the potential for severe early dying to occur. Modelling the impact of early dying on plant growth and yield as a function of environmental parameters and presence of inoculum may provide a means of setting confidence limits of an estimated disease severity and yield loss based on historical knowledge or knowledge of inoculum load.     

Water loss from potato tuber discs: a method for assessing wound healing

Summary A rapid and simple method for assessing wound healing in dises of potato tuber tissue has been developed. The rate of water loss is measured when batches of six dises are briefly exposed in a stream of air. The rate of water loss shows little change during the early stages of wound healing but decreases rapidly later.     

Implications of nitrogen fertilizer applications and extended grazing for the N economy of grassland

The response of swards which have been previously grazed to N fertilizer applied in early February was studied in two experiments in Northern Ireland. The effect of N fertilizer applied at a range of dates in autumn and spring on swards for out-of-season utilization was studied in a further experiment. Deep soil coring was also undertaken, subsequent to grazing with dairy cows, in grazed and protected areas in November and March to investigate the effect of out-of-season grazing on soil mineral N levels.
Dry-matter (DM) yield response to early spring N application in previously grazed swards was low, with no effect on DM yield in February or March. Progressively delaying N application (and commencement of herbage accumulation) in autumn from 8 September until 18 October reduced herbage availability in late autumn and early spring but increased leaf lamina content. The greater the amount of herbage accumulated to 1 December, the lower the tiller density in the following April.
N fertilizer had a greater impact on soil mineral N in spring than in late autumn/early winter, suggesting that fertilizer N was more prone to loss in the latter. Soil mineral N was not significantly affected by out-of-season grazing.
It is concluded that in well-fertilized, previously grazed swards response to N for out-of-season herbage is low and the probability for N loss is increased. Herbage quality will decline and the sward may be damaged if about 2 t DM ha⁻¹ or more of harvestable herbage accumulates for use in winter or in early spring.     

Brown Stink Bug (Hemiptera: Pentatomidae) Damage to Seedling Corn and Impact on Grain Yield

Brown stink bugs, Euschistus servus, are an important early-season pest of field corn in the southeastern United States. Feeding in the early stages of corn development can lead to a number of growth deformities and deficiencies and, ultimately, a reduction in yield. An observational and two experimentally manipulated trials were conducted in 2017 and 2018 to 1) determine optimal timing for assessing brown stink bug damage, 2) assess the level of damage from which yield compensation can occur, and 3) examine the relationship between brown stink bug density and early-season damage and yield. Fields were identified with infestations of brown stink bugs and a damage rating system for early stages of corn was established. Varying rates of brown stink bug densities were introduced using field cages and damage was assessed throughout the season. The density and duration of stink bug infestations were critical factors for damage potential, with each day of active feeding per plant resulting in a loss of ~14 kg/ha in yield. The level of damage in early stages of corn was categorized into easily identifiable groups, with only the most severe damage leading to a reduction in yield. Moderate and minimal feeding damage did not result in yield loss. This study emphasizes the need for early and frequent scouting of corn to determine the risk of damage and yield loss from brown stink bugs. Results from this study can be used to help develop management programs for brown stink bugs in the early vegetative stages of field corn.     

信阳茶园假眼小绿叶蝉发生特点及危害损失研究

本文通过系统调查研究信阳茶园假眼小绿叶蝉的发生规律，并利用网罩法测定了不同虫口密度对茶叶产量损失的影响。结果表明：假眼小绿叶蝉在信阳地区每年出现2个发生高峰，第1个出现在6月下旬至7月上中旬，第2个出现在9月上中旬；建立了不同虫口密度与产量损失的关系式为Y=0．2303X-0．5026和Y=0．2854X-0．8795（Y-产量损失；X-百叶虫数）。研究结果能为我们制定信阳地区假眼小绿叶蝉的预报预警和防控防治措施提供借鉴。     

Yield loss prediction models based on early estimation of weed pressure

Weed control thresholds have been used to reduce costs and avoid unacceptable yield loss. Estimation of weed infestation has often been based on counts of weed plants per unit area or measurement of their relative leaf area index. Various linear, hyperbolic, and sigmoidal regression models have been proposed to predict yield loss, relative to yield in weed free environment from early measurements of weed infestation. The models are integrated in some weed management advisory systems. Generally, the recommendations from the advisory systems are applied to the whole field, but weed control thresholds are more relevant for site-specific weed management, because weeds are unevenly distributed in fields. Precision of prediction of yield loss is influenced by various factors such as locations, yield potential at the site, variation in competitive ability of mix stands of weed species and emergence time of weeds relative to crop. The aim of the review is to analyze various approaches to estimate infestation of weeds and the literature about yield loss prediction for multispecies. We discuss limitations of regression models and possible modifications to include the influential factors related to locations and species composition in context of their implementation in real time patch spraying.     

Multiple heat and drought events affect grain yield and accumulations of high molecular weight glutenin subunits and glutenin macropolymers in wheat

Spring wheat plants were subjected to water deficit and/or high temperature episodes at spikelet initiation, anthesis or both stages. The stresses modified the early dough stage and maturity, shortened the kernel desiccation period and caused grain yield loss. Plants subjected to stress at the early growth stages had higher grain yields than the non-early-stressed plants when stress reoccurred at anthesis. Concentrations of high molecular weight glutenin subunits in grain were up-regulated by the single early drought, the early drought combined with late heat and the double drought stress treatments, but was down-regulated by the early heat and double heat stress events. Concentration of glutenin macropolymers was increased by the single early drought episode, the single late drought and heat events, as well as the early drought combined with the late heat stress, but was reduced by the early heat stress and double heat events.     

An Economic Analysis of the Effects of Harvest Timing on Yield,Quality, and Processing Contract Price for three Potato Varieties

Harvesting potatoes at or near physiological maturity increases the likelihood of producing high quality tubers which contributes to producing high quality processed end-product. Some growers harvest earlier than recommended in order to meet contract requirements and supply processors with early potatoes. Early harvest impacts the incentive-adjusted price (IAP) and revenue even after an early harvest incentive is applied. This study utilized a typical frozen processor contract and compared the economic impact of harvest timing (early, normal, and late) on the IAP of three potato varieties: Russet Burbank, Clearwater Russet, and Alpine Russet, grown in field trials at Parma, Idaho during 2014 and 2015. Contract quality incentives included percent of tubers greater than 170 g, percent sugar ends, percent of U.S. No. 1’s, and specific gravity. When compared to normal or late harvest, early harvest resulted in a decrease in the IAP and overall profit due to a significant reduction in specific gravity. Early harvest incentive did not offset the loss of revenue with Russet Burbank, but did offset revenue loss with Clearwater Russet and Alpine Russet. Clearwater Russet and Alpine Russet had significantly lower sugar end scores than Russet Burbank. Clearwater Russet consistently produced higher specific gravities and Alpine Russet produced larger tubers compared to Russet Burbank. Clearwater Russet and Alpine Russet have agronomic characteristics that can provide an increase in IAP over Russet Burbank.     

Potato yield losses due to early blight in Minnesota fields, 1981 and 1982

In both 1981 and 1982, 51 potato fields were surveyed every 7–10 days for early blight severity and fungicide use. Early blight severity data from each field were used as input to a regression model to estimate yield loss in that field. The model for early maturing potato cultivars was Percent Yield Loss=0.8183+0.6441* (% blight increment between days 56 and 66)+0.6102* (% blight increment between days 66 and 76)+1.3480* (% blight increment between days 76 and 86). The model for late maturing cultivars was Percent Yield Loss=2.1846-4.7734* (% blight on day 56)+0.7440* (% blight on day 76)+ 0.5676* (% blight on day 96). In both 1981 and 1982, early blight was found to be present in all fields of the survey. In 1981, early blight was estimated to have caused mean losses of 6.5% (Red River Valley), 3.7% (Central sands) and 2.3% (Southern muck). In 1982, losses from the same areas were 5.4%, 3.7% and 2.6% respectively. In 1981, individual county losses ranged from 2.3% for Freeborn to 12.9% for Marshall while in 1982 losses were from 2.0% for Freeborn to 6.7% for Clay. Although fungicide use data were incomplete, the county with lowest yield loss had the most fungicide applications.     

早稻穗期白背飞虱为害损失及防治指标研究

 笼罩接虫试验丧明，早稻穗期产量损失(Y )与每丛白背飞虱数量(x)的关系符台方程： Y=14.0835+10.9425X士28.95。 产量损失的主导原因是水稻受害后秕谷率增加。根据目前稻谷价格、防治费用等，导出白背飞虱防治指标为每丛l12～16头。经大田验证，与实际基本相符。     

THE EFFECT OF CONDITIONING ON THE RATE OF DRYING AND LOSS OF NUTRIENTS IN HAY

Treating cut herbage with a roller-crusher or a crimper resulted in an increased drying rate compared with tedding. A higher rate of drying was obtained when herbage was treated within a short period of the crop being cut, this effect being more marked with the crimper than with the tedder. Nutrient loss was higher when a crimper was used than with a roller-crusher or tedder. Applying water at an early stage in the drying process did not have a marked effect on nutrient loss, but appeared to decrease the digestibility of the crimped hay.     

云南马铃薯贮存损失的调查和评价

调查了云南马铃薯主产区 17个农户家庭贮存马铃薯的现状和损失。作为商品薯贮存失去商品价值的损失率达到 4 7 4 % ,其中发芽薯占 35 4 % ,损失最大 ,贮存时间 12 0d块茎发芽率仅1 5 % ,但 15 0d迅速增加到 5 6 88% ;破损块茎占 7 2 % ;病害烂薯占 4 8%。马铃薯种薯与商品薯同仓混贮 ,在同样无光照的条件下 ,造成种薯过早发芽 ,而且芽细弱 ,降低了种薯的质量。马铃薯疮痂病 (S .scabies)发生普遍 ,在一些地方发病率高达 10 0 % ,应当引起重视。讨论了马铃薯贮存中存在的问题 ,提出了马铃薯贮存技术发展的意见。     

Corn earworm (Lepidoptera: Noctuidae) damage at various kernel development stages on food maize

Feeding by corn earworm, Heliocoverpa zea (Boddie), larvae lowers the quality of food maize by causing damage to kernels that results in discoloration of food maize products during cooking. This damage includes kernel cracking or nipping of kernels by larvae. Larval infestations were highest from first silk to early dough growth stages. Infestations during the silk and blister-dough stages caused the least amount of kernel damage on an ear. The area on an ear exposed to corn earworm damage during the blister, dough, or dent to harvest treatments was similar. Kernels were most susceptible to quality loss when they were hardening. Yield was not affected by corn earworm feeding, but the highest quality loss occurred on ears exposed to earworms during the dent-harvest period and throughout the season. Consequently, late season control actions (during the dough stage) would be more effective for reducing quality loss from corn earworm feeding on food maize, than is the present practice of spraying during the green silk stage.     

Factors influencing reconditioning of Russet Burbank potatoes

Studies were made to determine factors which influence reconditioning of Russet Burbank tubers. Tubers from plants grown under low fertility were more difficult to recondition than tubers from plants adequately fertilized. Low specific gravity potatoes were also more difficult to recondition than high specific gravity potatoes even though the initial sugar content was approximately equal. The stem portion of Russet Burbank tubers lost considerably less sugars than the bud portion during the reconditioning process. It appears that factors which are responsible for high sugar development are also responsible for difficulty in sugar loss. Results also indicate greater difficulty in reconditioning early in the storage period with the loss of sugars becoming easier as the storage season progressed into spring.     

2006年尚志市水稻减产原因调查

根据田间调查资料,从品种选用不合理、育秧技术粗糙、插秧期拖后、障碍性冷害等八个方面分析了2006年尚志市水稻减产原因。依据当地地理、气候等条件,提出了选择优质、高产、抗逆品种;坚持标准化育苗,适时抢早;进行测土配方施肥;及时防治病虫草害等一系列措施。     

大豆花叶病毒（SMV）流行的产量损失及其模型预测

网室接种和田间调查测定SMV引致大豆的产量损失证明,SMV侵染大豆植株愈是在生育早期产量损失愈重。盛花期以后发病的植株产量损失显著减小,鼓粒初期的病株几乎无产量损失。SMV不同毒株引致的产量损失显著不同,强毒株的侵染,引致感病品种的产量损失平均超过弱毒株的40％。根据不同初侵染水平的30组SMV流行与产量损失数据,采用逐步回归分析,建立了准确度较高的产量损失预测多点模型和单点模型。根据损失测定,大豆盛花期的SMV病株率低于3％可控制SMV流行所造成的产量损失。     

Etiology of potato early dying in Delaware

Greenhouse and field plot experiments along with surveys of commercial potato fields were conducted to determine the etiology of potato early dying in Delaware and its impact on yield ofSolanum tuberosum cultivar Superior.Verticillium dahliae was the primary pathogen causing early dying, and no increase in disease severity or yield loss was observed when plants were inoculated with bothV. dahliae andColletotrichum coccodes. The field survey showed thatV. dahliae was the predominant pathogen in symptomatic plants, and nematodes were not essential in association withVerticillium to cause early dying. Disease severity was the same in the presence of a low population or absence of nematodes.     

2006年尚志市水稻减产原因调查

根据田间调查资料,从品种选用不合理、育秧技术粗糙、插秧期拖后、障碍性冷害等八个方面分析了2006年尚志市水稻减产原因。依据当地地理、气候等条件,提出了选择优质、高产、抗逆品种;坚持标准化育苗,适时抢早;进行测土配方施肥;及时防治病虫草害等一系列措施。     

Growing point dynamics and spring growth of white clover in a mixed sward and the effects of nitrogen application

The effects of N applied in spring on the growth and development of white clover ( Trifolium repens L.) in a mixed sward were investigated at Uppsala, Sweden. In early spring, the plots received 0 or 90 kg N ha⁻¹ in the form of nitrochalk. The formation and loss of stolon branches were followed on marked stolons. The proportion of white clover in the total above-ground dry matter (DM) of the sward fell substantially in both treatments during the 8-week growth period, but more so in N fertilized than in unfertilized plots; fertilizer N increased the accumulation of grass DM, whereas it reduced the accumulation of white clover DM. Over time, there was a loss of white clover growing points and this loss was greatest in plots where N was applied. Branching occurred predominantly during the first half of the growth period and was unaffected by N application, whereas the loss of branches was more confined to the latter period and was increased in plots receiving N. Irrespective of node position, the size of the branches that died was comparatively small, and more branches were lost from young than from old node positions. It is concluded that the decline in the number of growing points in the N fertilized sward was mainly due to an increased loss of recently formed branches. As a consequence of its stimulating effect on grass growth, the N fertilized treatment initially led to a reduction in the R:FR ratio of light and subsequently also in the availability of photosynthetically active radiation within the canopy. These changes in the light environment of the sward caused morphological adjustments to be made by the white clover and may have contributed to the observed loss of branches.