不同播期对冀东地区玉米田禾蓟马发生量和玉米产量的影响

为了探索冀东地区玉米播期与禾蓟马发生量和玉米产量之间的关系,以生产常用玉米品种郑单958为试材,在4月30日～7月19日每隔10d设定1个播期,研究了9个不同播期处理对禾蓟马发生量和玉米产量的影响,以确定冀东地区玉米禾蓟马为害率较低且产量较高的适宜播种日期。结果表明：随着播期的推迟,禾蓟马发生量呈增加一减少一增加的趋势,玉米产量呈减少一增加一减少的趋势,其中,4月30日播种的玉米未见到禾蓟马发生、产量最高,5月10日和6月29日播种的玉米虫害率较低、产量较高,但3个播期处理的玉米产量差异均不显著。建议冀东地区春播玉米选择4月30日～5月10日播种,夏播玉米选择6月29日前后播种,以降低禾蓟马对玉米产量的影响。     

水稻叶色突变对虫害发生影响的研究初报

为明确叶色标记水稻在生产中可能引起的虫害发生变化,本试验在使用和不使用农药防治的情况下,以常规品种嘉禾218为对照,对龙特甫B及其2个叶色突变系黄玉B、翠玉B田间虫害情况进行了调查.龙特甫B为正常绿叶籼稻品种,黄玉B、翠玉B全生育期分别表现黄色和翠绿色,在苗期、分蘖期和抽穗期,黄玉B较龙特甫B的叶绿素含量分别下降58.O%,48.4%和40.8%,翠玉B则分别下降39.5%,36.0%和29.5%.结果表明,秧田期2个叶色突变体上的稻蓟马虫量显著高于其亲本龙特甫B;本田期灰飞虱和褐飞虱的虫口数在不同材料间或差异不显著,或存在显著差异,但没有一定的规律性.但是,2个突变体受稻纵卷叶螟的危害显著轻于龙特甫B,表现为盛发期突变体受稻纵卷叶螟危害产生的虫苞数显著少于龙特甫B,而龙特甫B与嘉禾218之间没有显著差异;相反,2个突变体植株上白背飞虱的虫量显著大于龙特甫B,龙特甫B也显著大于嘉禾218.根据植株的农艺性状和叶绿素含量,以及虫害发生动态变化,笔者推测,造成叶色标记水稻稻纵卷叶螟危害变轻的原因可能与植株叶绿素含量下降,影响幼虫生长发育有关,但引起白背飞虱虫口增加的原因尚需进一步研究.本试验为首次对叶色标记水稻虫害发生情况进行研究,所得结果不但对完善叶色标记水稻生产体系具有指导意义,同时对研究害虫与水稻叶色之间的关系也具有理论价值.     

氯虫苯甲酰胺在水稻及稻田环境中的残留动态

采用田间试验方法,研究了氯虫苯甲酰胺在稻田水、土壤和水稻植株中的消解动态,测定了氯虫苯甲酰胺在水稻和土壤中的最终残留量。稻田水和土壤样品采用丙酮提取,水稻样品用乙腈溶液浸泡提取,经玻璃层析柱净化,HPLC紫外分析测定。结果表明,稻田水、土壤、水稻植株、谷壳、糙米中氯虫苯甲酰胺添加浓度为0.005~1.0mg/kg时,平均回收率为85.06%~95.83%,变异系数在2.08%~5.77%之间。方法的最低检测浓度为:稻田水0.005mg/kg,土壤0.01mg/kg,水稻植株0.02mg/kg,谷壳0.02mg/kg,糙米0.01mg/kg。氯虫苯甲酰胺在稻田水、土壤和水稻植株中的消解动态均符合一级动力学方程,半衰期分别为3.1~5.0d、6.6~9.0d、8.0~9.9d。以33.86g/hm2和50.80g/hm2间隔14d施用氯虫苯甲酰胺2次和3次,末次施药21d后氯虫苯甲酰胺的最高残留量为:土壤0.217mg/kg,水稻植株0.879mg/kg,谷壳0.389mg/kg,糙米0.018mg/kg。氯虫苯甲酰胺在糙米中的残留量低于我国和食品法典委员会(CAC)及欧盟的最大残留限量(MRL)标准。     

融入监督信息的k—mean聚类瓜蓟马预警模型

[目的]为提高瓜蓟马病虫害的预警效果。[方法]采用k-mean聚类建立了瓜蓟马预警模型,并针对瓜蓟马数据中在k-mean聚类算法下难以判断的情况,引入了监督信息,即模糊关联规则进行进一步划分。[结果]引入监督信息的k-mean聚类算法的预警准确率比最近邻算法、k-mean聚类和支持向量机预警准确率都要高。[结论]k-mean聚类过程中引入模糊关联规则能较有效地提高预警准确率。     

西花蓟马在烟草植株上的分布特点及防治技术

西花蓟马近年来传入我国,已对我国部分地区的农作物产生了巨大的危害。以西花蓟马在烟草植株上的分布为基础,介绍了西花蓟马在烟草上不同部位、不同方向和正背面等的分布和取食危害特点。以此为基础,提出了综合防治的方法,其中主要介绍了物理防治和化学防治方法。     

花生花蓟马室内药剂筛选及田间药效试验

采用浸叶法在室内对花蓟马进行了药剂筛选试验,并对毒效较高的3种药剂开展了进一步毒力测定和田间药效试验。结果表明,有机磷类的三唑磷和乐斯本,拟除虫菊酯类的高效氯氰菊酯、溴氰菊酯和高效氯氟氰菊酯,以及氨基甲酸酯类的丁硫克百威等药剂对花蓟马的毒效很低,致死率均在37．6％以下。阿维菌素、啶虫脒和吡虫啉对花蓟马的致死作用明显,致死率分别为98．3％、98．7％和66．8％,它们的LC50分别为0．97mg·L^-1、15．4mg·L^-1和42．4mg·L^-1,以阿维菌素的毒力最高,是吡虫啉的43．71倍。田间药效试验结果与室内毒力测定结果相符合,以阿维菌素的防效最高,达93．3％以上,且持效期较长,施药后12d的防效仍在90％以上,是防治花生花蓟马的首选药剂。     

Cropping System Intensification as a Management Method Against Vectors of Viruses Causing Maize Lethal Necrosis Disease in Kenya

Maize Lethal Necrosis Disease (MLND) has emerged as a great threat to maize production in East Africa. It is caused by a synergistic infection of maize by sugarcane mosaic virus (SCMV) and maize chlorotic mottle virus (MCMV). This study was carried out in Bomet County, Kenya, to determine the potential of various cropping systems to manage vectors of MLND–causing viruses. Plots measuring 7.5 m × 5.25 m were planted with maize (Zea mays L.) intercropped or bordered by elephant grass (Pennisetum purpureum Schumach.), coriander (Coriandrum sativum L.), pearl millet (Pennisetum glaucum (L.) R. Br.) and Gadam sorghum (Sorghum bicolour (L.) Moench). Maize monoculture was used as a control treatment; the nine treatments were arranged in a randomized complete block design and replicated four times for two seasons (December 2014 to April 2015 and April 2015 to September 2015). Data on corn thrips and corn leaf aphid infestation, MLND severity and incidence, MCMV and SCMV viral load, and yield were recorded. The sorghum border was the only companion crop that tested positive for MCMV and none tested positive for SCMV. Maize intercropped with elephant grass had significantly (P?<?0.01) the least incidence of disease. However, this treatment produced significantly lower yields (P?<?0.01). Coriander was the only companion plant most preferred by both corn thrips and corn leaf aphids (P?<?0.001). Maize from all cropping systems tested positive for MCMV (P?<?0.001) while maize grown with coriander tested negative for SCMV (P?<?0.001). Yields from plots surrounded by sorghum and coriander were significantly similar to those from maize monoculture plots. These findings suggest that maize should be intercropped with coriander due to its potential to trap corn leaf aphids and protect maize from SCMV. In addition maize should be grown surrounded by a sorghum border to maximize yield in areas where MLND is prevalent.     

Comparative analyses of the toxic effects of imidacloprid and spirotetramat on Frankliniella occidentalis (Pergande), the vector of tomato zonate spot virus: a laboratory assay

The tomato zonate spot virus (TZSV) is responsible for substantial yield losses in vegetables, tobacco and other cash crops in China in recent years. The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera, Thripidae), is the main vector of TZSV in Yunnan Province. Because controlling the population of insect vectors is the most efficient way to prevent epidemics of viral diseases, we conducted laboratory assays to assess the potential of using spirotetramat as an alternative to imidacloprid in controlling F. occidentalis. Our results demonstrated that spirotetramat was significantly more lethal than imidacloprid to F. occidentalis at different concentrations. The LC₃₀, LC₅₀ and LC₉₀ values of spirotetramat were all much lower than those of imidacloprid after the same time of treatment. Frankliniella occidentalis was more sensitive when treated with spirotetramat than imidacloprid at the concentrations of 500, 250, 125 and 62.5mg/L, and the median lethal concentrations (LC₅₀) were 285.53, 82.24 and 11.19mg/L at 12, 36 and 72 hours after treatment, respectively. Spirotetramat caused 100% mortality of F. occidentalis at 500 and 250 mg/L after 48 hours treatment, and at the lowest concentration 125 mg/L at 72 hours after treatment, respectively. Field experiments carried out elsewhere have confirmed our findings. Together they allow us to conclude that spirotetramat is a promising pesticide for the control F. occidentalis in China.     

Detection of Thrips Defect on Green-Peel Citrus Using Hyperspectral Imaging Technology Combining PCA and B-Spline Lighting Correction Method

In order to find an effective method of detecting thrips defect on green-peel citrus, a defect segmentation method was developed using a single threshold value based on combination of characteristic wavelengths principal component analysis （PCA） and B-spline lighting correction method in this study. At first, four characteristic wavelengths （523, 587, 700 and 768 nm） were obtained using PCA of Vis-NIR （visible and near-infrared） bands and analysis of weighting coefficients; secondarily, PCA was performed using characteristic wavelengths and the second principal component （PC2） was selected to classify images; then, B-spline lighting correction method was proposed to overcome the influence of lighting non-uniform on citrus when thrips defect was segmented; finally, thrips defect on citrus was extracted by global threshold segmentation and morphological image processing. The experimental results show that thrips defect in citrus can be detected with an accuracy of 96.5% by characteristic wavelengths PCA and B-spline lighting correction method. This study shows that thrips defect on green-peel citrus can be effectively identified using hyperspectral imaging technology.