Using remote sensing to predict outbreaks of Oestrus ovis in Namibia

The Directorate of Veterinary Services of the Ministry of Agriculture, Water and Rural Development of Namibia issues warnings to farmers in the south of the country about the likelihood of infestation of small-stock by the nasal bot fly, Oestrus ovis. Farmers can then treat their stock at the most appropriate time. The O. ovis puparia develop at shallow depths in the soil and the timing of emergence is directly dependent on climatic conditions, specifically the number of degree-days above a particular threshold soil temperature. Based on temperature measurements from only a few stations scattered throughout the country, the veterinary department warnings lack precision in space and time. This paper presents an attempt to support the programme of warnings with accumulated temperature information from Meteosat satellite images, in order to strengthen predictions of the time of emergence in specific places, and to improve the precision and reliability of warnings given to farmers.     

不同小麦品种籽粒灌浆特性的研究

以黄淮南片主产麦区广泛种植和新近育成推广的12个小麦品种为供试材料,对籽粒灌浆特性进行研究.结果表明:籽粒平均灌浆速度及最大灌浆速度均与百粒重、籽粒体积和籽粒最大体积呈极显著的正相关;籽粒灌浆持续期仅与饱满指数呈显著的正相关,而与百粒重无显著相关.供试品种的籽粒平均灌浆速度和最大灌浆速度,均以郑州853、陕农7859为最快,灌浆持续期最短,属晚花基因型品种;冀麦5418和徐州21的灌浆持续期最长,属早花基因型品种.还探讨了黄淮麦区南片小麦籽粒灌浆模式.     

积温及热量资源概念的科学性问题与改进

积温与热量资源的概念广泛存在于国内文献及教材,但其传统定义有违物理学原理,英译用词及度量单位也不统一,需要给予准确的科学诠释并进一步规范化。本文分析了Web of Science的相关文献,综述了积温与热量资源概念的由来与发展,提出了应用中存在的问题。研究表明：虽然积温作为农业热量资源的主要指标并广泛应用,但植物和变温动物完成某个阶段的生长发育并非需要一定数量的积温,而是需要适宜温度条件和必要的持续时间;过高的温度或过多的热量反而可造成伤害,有时有的物种反而需要相对较低的温度条件。建议将“热量资源”改称“温度资源”,即有利于植物与变温动物生长发育的温度条件与其持续时间的综合,从而赋予积温和温度资源充分的生物学与物理学意义。     

Color preference,seasonality, spatial distribution and species composition of thrips (Thysanoptera: Thripidae) in northern highbush blueberries

We investigated color preference, seasonal abundance, spatial distribution and species composition of thrips in northern highbush blueberries, Vaccinium corymbosum L., in New Jersey (USA). White sticky traps were more attractive to thrips compared with yellow or blue traps. Thrips captures using white sticky traps showed that their flight activity begins 20–30 d after the onset of flowering, with 10, 50 and 90% of trap captures observed at 383, 647 and 1231 degree-day accumulations, respectively (10 °C base temperature). Two methods were used to study thrips distribution within a blueberry bush. First, white sticky traps were placed within the bush canopy at three different heights. The highest numbers of thrips were caught on traps in the middle and top one-third of the canopy while the lowest numbers were caught in the bottom one-third. A second method determined the distribution of thrips on the blueberry plant at different heights and phenological stages. The highest numbers of thrips were found on young leaves at lower parts of the canopy, whereas flowers and fruit had fewer thrips and none were found on buds; these thrips were identified as, Scirtothrips ruthveni (88% of adults) and Frankliniella tritici (12%). The distribution of thrips within a blueberry planting was investigated using an evenly-spaced grid of white sticky traps in combination with on bush beating-tray samples. Thrips counts from traps correlated with direct counts on the bush across the entire blueberry field (macro-scale level); however, within the field (micro-scale level), there was no correlation between the number of thrips on traps and on individual bushes near traps. Early in the season, trap counts were higher on bushes closer to the forest, indicative of movement of thrips from wild hosts into blueberry fields. However, this was not the case for direct on bush counts or trap counts for the later part of the season, where there was no clear forest “edge” effect. Percent fruit injury due to thrips feeding was low, and it correlated with thrips counts on bushes but not from counts on traps. Overall, our data show that thrips counts on sticky traps need to be interpreted with care because these numbers weakly correlated with the numbers of thrips on bushes at the micro-scale level and percent fruit injury; however, they can be useful predictors of thrips activity across entire blueberry fields (macro-scale).     

Comparison of degree-day distribution models for predicting emergence of the cabbage aphid on canola

Cabbage aphid, Brevicoryne brassicae (L.), is a serious pest on canola, Brassica napus L. Estimation of required degree-days for 50% emergence of the population is of special interest for controlling this aphid. To precisely predict 50% emergence of aphid populations as a function of accumulated degree-days, eight distribution models were tested. Models were evaluated statistically and validated with a separate data set collected from three canola fields. Observed cumulative emergence of the aphid was well described by three models. The sigmoid model proposed by Brown and Mayer was recommended to describe 50% emergence of the cabbage aphid population, because the model is simple and the parameter b denotes the accumulated degree-days at 50% emergence. The selected model could be used to better time insecticide applications and to more efficiently forecast aphids in canola fields.     

关于积温一词及其度量单位科学性问题的讨论

积温是农业气象及相关学科常用的一个基本概念,但长期以来对于其科学意义和度量单位的认识很不一致。本文回顾了积温概念的由来和发展,评述了积温概念在科学性上存在的问题,介绍了国内外的有关修正和改进工作,特别是英国学者J.L.Monteith应用热时理论对于积温本质做出的科学阐述。通过对文摘数据库CAB中1990-2008年10月发表的科技文献检索结果的统计分析,比较了积温及其同义词在文献题目中的应用频率和地域分布特征,表明国际学术界的主流正在日益摈弃传统积温概念的不科学表述形式。为改变目前农业气象界在积温概念及其度量单位上的混乱状态,结合第二届科学名词审定工作,建议赋予"积温"和"热量资源"名词以新的表述方式,使之既不违背物理学原理,又能照顾目前已被广泛使用而约定俗成的现状,以利农业气象学科的健康发展和促进农业气象科技的广泛应用。     

Using degree-day accumulations and host phenology for predicting larval emergence patterns of the olive psyllid, <Emphasis Type="Italic">Euphyllura phillyreae</Emphasis>

The olive psyllid, Euphyllura phillyreae Foerster is one of the most destructive pests on buds and flowers of olive tree (Olea europaea L.) in May when the olive growers cannot apply any insecticides against the pest. Temperature-dependent development of the psyllid was studied at constant temperatures ranged 16–26°C. A degree-day (DD) model was developed to predict the larval emergence using the weekly cumulative larval counts and daily mean temperatures. Linear regression analysis estimated a lower developmental threshold of 4.1 and 4.3°C and a thermal constant of 164.17 and 466.13 DD for development of egg and larva, respectively. The cumulative larval counts of E. phillyreae approximated by probit transformation were plotted against time, expressed as the sum of DD above 4.3°C, the starting date when the olive tree phenology was the period of flower cluster initiation. A linear model was used to describe the relationship of DDs and probit values of larval emergence patterns of E. phillyreae and predicted that 10, 50 and 95% emergence of the larvae required 235.81, 360.22 and 519.93 DD, respectively, with errors of 1–3 days compared to observed values. Based on biofix depends the development of olive tree phenology; the DD model can be used as a forecasting method for proper timing of insecticide applications against E. phillyreae larvae in olive groves.     

Temperature-dependent development of <Emphasis Type="Italic">Diglyphus isaea</Emphasis> (Hymenoptera: Eulophidae) on <Emphasis Type="Italic">Liriomyza sativae</Emphasis> (Diptera: Agromyzidae) on cucumber

The development of Diglyphus isaea (Walker), a parasitoid of leafminers, was studied under laboratory conditions at seven constant temperatures (10, 15, 20, 25, 30, 35, and 40°C) on Liriomyza sativae Blanchard reared on cucumber (Cucumis sativus L.). The total development period (oviposition to adult emergence) decreased with increasing temperature between 15 and 35°C. In 10 and 40°C no development rate was found in D. isaea, so that it may be claimed that these temperatures fall outside the temperature range for development. Linear regression was used to describe the relationship between development rate and temperature. For egg to adult development, males of D. isaea required 153.8 degree-days (DD) above the theoretical threshold of 9.2°C and females required 161.3 DD above 9.4°C. Data were fitted to four nonlinear temperature-dependent models. Evaluation of the models took place based on the following criteria: fit to data, number and biological value of the fitted coefficient, and accuracy on the estimation of the thresholds. It could be concluded that the Briere-1 and Briere-2 models are suitable for estimating the minimum, maximum and optimal temperature thresholds of D. isaea. Thermal requirements and temperature thresholds can be used to predict the occurrence, number of generations and population dynamics of D. isaea.