On the optimum grid size in field experiments without replications

Summary In unreplicated field trials a correction for soil heterogeneity is easily achieved by gridding, i.e. by expressing the observations as deviations from a local average. This paper investigates the problem of determining the optimum size of such a neighbourhood to be used in a moving average. The optimum grid size depends on two parameters, i.e. the coarseness of the spatial variation of the trial field and the ratio of genotypic vs. non-genotypic variance. In general these parameters are not known to the breeder. We introduce a method for estimating these parameters from the data. From these estimates the optimum grid size can be obtained using tables presented in this paper.The method has been evaluated by applying it to a series of simulated data. It turned out that the agreement between estimated and true optimum grid size was satisfactory in these simulations.Some theoretical aspects of the results are discussed.     

Methods of analysis for studying cocoa (theobroma cacao L.) susceptibility to mirids

Two species of mirids, Distantiella theobromae (Dist.) and Sahlbergella singularis Hagl., cause substantial damage to cocoa plantations in West Africa. Cocoa susceptibility to mirid attack was observed in the Côte d’Ivoire in a trial involving progenies obtained from crosses according to a factorial mating design, and in a trial involving clones. As spatial distribution of mirid damage was not uniform within the plots, a method was developed for experimental design of completely randomized single-tree elementary plots, based on analysis of covariance and taking into account the spatial within-plot effect of the damage caused. This method resulted into a more precise estimation of genetic effects and heritabilities adjusting for mirid susceptibility heterogeneity in the field.     

Local adjustment method for field experiments. 1. The method and its examination by computer simulation

Summary The modification of the nearest neighbour method for using various size plots in field trials has been developed and the results of testing its validity by computer simulation are presented. It was found that the Field-S variant of this method using a square pilot area is the best for fields with a low and medium spatial heterogeneity. The Field-L variant using the least quantity of neighbours, offers advantages for fields with a medium and high spatial effect. The optimal values of the controlling coefficients of these variants were computed to allow for the calculation of the environmental indices over a wide interval of spatial heterogeneity with sufficient accuracy. For this reason, this local adjustment method is recommended as an obligatory statistical procedure for a prior data analysis of any field experiments that have fulfilled the necessary requirements. The original Field and CRBSD programs using the local adjustment method developed have been created for IBM-compatible personal computers.     

COMPUTER GENERAL EXPRESSIONS OF BASIC PROBLEMS UNDER ADJUSTMENT OF OBSERVATION EQUATION

This paper presents computer general expressions which include: (1) calculation of the coefficient of normal equation; (2) calculation of the reduced coefficient; (3)calculation of [PVV]; (4)calculation of the correlate; (5) calculation of the weighted reciprocal(1/PF) of the function of adjusted value. Each calculation is written in a corresponding program. As a program block, it may be called anywhere in the course of surveying computation.     

Quantifying spatio-temporal dispersion of bark beetle infestations in epidemic and non-epidemic conditions

Spatio-temporal dispersal of pest species such as bark beetles plays a key role in their population ecology and outbreak dynamics. Understanding the underlying patterns is crucial for applying appropriate management strategies.In contrast to most existing studies which focus on dispersing beetles, we analysed patches of killed trees resulting from bark beetle infestation. The study was based on a 22-year time series of annually captured colour-infrared (CIR) images of the Bavarian Forest National Park (Germany), where Ips typographus L. (Coleoptera, Curculionidae, Scolytinae) propagates undisturbed by human activity. Newly infested patches comprising at least 5 spruce trees were identified in every time step. This investigation of spatio-temporal spread of infestations primarily focused on (i) parameterizing the size and shape of infestation patches, (ii) modelling an infestation gradient and (iii) evaluating the risk of subsequent infestations on landscape scale. We developed a GIS-based distance ring approach to quantify the distance relation of subsequent infestations, including the distribution of potential hosts.Infestation spread was revealed to be strongly distance dependent, following an inverse power law function: on average 65% of new infestations occurred within a 100 m radius of the previous year’s infestations, and 95% within 500 m. ‘Distance’ proved to be a major determinant of I. typographus dispersal on the landscape scale in each time step of the 22-year series we investigated. Infestation distance thus describes the outcome of beetle dispersal very accurately. The time series showed two alternating periods of epidemic and non-epidemic infestation. These gradation stages did not affect the size and shape of infested patches, but epidemics correlated significantly with a higher percentage of infestations within short distances. Additionally, the resulting infestation risk is highly sensitive to the gradation stage, particularly within the first 100 m around source spots where it increases up to 30%.Our study therefore contributes to a better understanding of the outbreak dynamics of I. typographus and suggests concentrating efficient bark beetle management on areas in the close vicinity of previous years’ infestations.     

小麦多小穗品系“10-A”4个特异性状的基因效应及其相关分析

本文以每穗小穗数可多达37个的不分枝普通小穗品系“10-A”为母本，与一系列遗传差异较大的测验系组配的20个组合的P1、P2、F1、F2、B1和B2六个世代为供试材料，考察了“10-A”最优良的性状（小穗数）和3个突出的不良性状（抽穗期、穗粒数和粒重）。采用明道绪最近提出的“利用各世代的小区平均数估计遗传参数的加权最小二乘     

MAGNETIC RESONANCE IMAGING APPARENT DIFFUSION COEFFICIENTS FOR HISTOLOGICALLY CONFIRMED INTRACRANIAL LESIONS IN DOGS

Diffusion‐weighted imaging is an advanced magnetic resonance imaging technique that is well established in the diagnosis of nonhemorrhagic infarction in people. However, recent investigations into intracranial neoplastic and inflammatory disease in people have identified variable and overlapping results. In this retrospective study of 37 dogs with histologically confirmed intracranial disease, we investigated whether histogram analysis of quantitative apparent diffusion coefficients (ADC) can differentiate specific disease processes. Disease categories included: meningiomas, glial cell tumors, choroid plexus tumors, pituitary tumors, inflammatory brain diseases, acute nonhemorrhagic infarcts, chronic nonhemorrhagic infarcts, and hemorrhagic infarcts. A wide range of ADC value distributions were identified within the disease groups, and there were overlapping ADC values between most groups. Low ADC values indicating restricted diffusion of water were identified in acute nonhemorrhagic infarcts as expected, but were also seen in meningiomas, glial cell tumors, and granulomatous meningoencephalitis. Based on this preliminary data it is unlikely that singular quantitative ADC values can be used to determine the histological type of canine intracranial disease.     

疾病治疗方法疗效的统计分析

本文提出一种新的疗效分析法－加权分析。由于此法吸取了疗效程度差异的信息，因而能更科学，更有效地鉴别各种治疗方法（对同一种疾病）疗效的优劣，本文还提供了衡量疗效的加权均值理论值的点估计和区间估计－即预测疗效的置信区间。     

无单元伽辽金法求解不可压Navier-Stokes方程

用无单元伽辽金法(EFGM)求解了不可压的Navier-Stokes方程，由加权残值法推导了系统无单元伽辽金法离散的Navier-Stokes方程，在时间域上采用分步格式计算，使速度和压力采用同阶线性插值并由相互独立的方程以解耦的形式求解，在每一时间步中，对压力解和速度解采用了Newton-Raphson迭代法进行修正、最后将所得到的方法应用到Couette流中，验证了本文方法的有效性。     

Quantifying inherent predictability and spatial synchrony in the aphid vector Myzus persicae: field-scale patterns of abundance and regional forecasting error in the UK

Background

Sugar beet is threatened by virus yellows, a disease complex vectored by aphids that reduces sugar content. We present an analysis of Myzus persicae population dynamics with and without neonicotinoid seed treatment. We use 6 years' yellow water trap and field-collected aphid data and two decades of 12.2 m suction-trap aphid migration data. We investigate both spatial synchrony and forecasting error to understand the structure and spatial scale of field counts and why forecasting aphid migrants lacks accuracy. Our aim is to derive statistical parameters to inform regionwide pest management strategies.

Results

Spatial synchrony, indicating the coincident change in counts across the region over time, is rarely present and is best described as stochastic. Uniquely, early season field populations in 2019 did show spatial synchrony to 90 km compared to the overall average weekly correlation length of 23 km. However, 70% of the time series were spatially heterogenous, indicating patchy between-field dynamics. Field counts lacked the same seasonal trend and did not peak in the same week. Forecasts tended to under-predict mid-season log₁₀ counts. A strongly negative correlation between forecasting error and the proportion of zeros was shown.

Conclusion

Field populations are unpredictable and stochastic, regardless of neonicotinoid seed treatment. This outcome presents a problem for decision-support that cannot usefully provide a single regionwide solution. Weighted permutation entropy inferred that M. persicae 12.2 m suction-trap time series had moderate to low intrinsic predictability. Early warning using a migration model tended to predict counts at lower levels than observed. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.