Effects of buprofezin and diflubenzuron on various developmental stages of Asian citrus psyllid, Diaphorina citri

BACKGROUND: Diaphorina citri populations in Florida are developing resistance to commonly used neurotoxic insecticides. Alternatives to neurotoxins, such as insect growth regulators, are needed to control this season-long subtropical pest to prevent or delay development of insecticide resistance. In the present investigation, two insect growth regulators (IGRs), buprofezin and diflubenzuron, were evaluated against various developmental stages of D. citri. RESULTS: The 0–1-day-old D. citri eggs were more susceptible to buprofezin and diflubenzuron than the 3–4-day-old eggs. Adult emergence was completely suppressed by treating first- or third-instar nymphs with buprofezin or diflubenzuron at 30–240 or 23–184 µg mL⁻¹ rates respectively. Treatment of fifth-instar nymphs with diflubenzuron at a rate of 184 µg mL⁻¹ and with buprofezin at 30–240 µg mL⁻¹ rates resulted in approximately 20 and 15–80% reductions in adult emergence respectively. The mean number of eggs per plant was reduced at 5 days after topical treatment with diflubenzuron. Mean egg hatch per plant was reduced at 5 and 6–15 days after topical treatments with buprofezin and diflubenzuron respectively. CONCLUSION: Buprofezin and diflubenzuron effectively suppressed D. citri adult emergence. D. citri were more susceptible as early (first–third-instar) than late (fifth-instar) nymphs. Both IGRs inhibited egg production and egg hatch. Reduction in the number of subsequent offspring suggests reduced vertical transmission of Candidatus Liberibacter asiaticus, the pathogen thought to cause citrus greening disease. The present results indicate that both IGRs tested here should be effective tools for rotation in insecticide-based D. citri management programs. Copyright © 2012 Society of Chemical Industry     

田间柑橘植株不同部位黄龙病菌的PCR检测及发病原因分析

［目的］了解黄龙病菌在柑橘植株不同部位的分布,为深入研究病菌在植株体内的扩散情况奠定基础;明确病害的发生原因为有效防控该病害提供借鉴。［方法］ 调查浙江省台州市柑橘黄龙病（huanglongbing, HLB）的发生情况,通过常规和巢式PCR,检测了发病情形不同的两个果园内柑橘病株不同部位及不同植株中的黄龙病菌,并对其发病原因进行分析。［结果］ 发现一果园内病株的无症状叶片、有症状叶片和枝条中均含有黄龙病菌,而其周围植株不含病菌;另一果园内病株的有症状叶片、枝条、主干和砧木中均含有黄龙病菌,而其周围植株也含菌。［结论］分析认为这两种果园内柑橘植株发病原因不同,一种可能为通过携带黄龙病菌的柑橘木虱所感染,另一种可能为嫁接过程中通过带菌的接穗感染。     

柑桔黄龙病病原和检测方法研究进展

介绍了柑桔黄龙病病原认识过程、病害田间诊断、指示植物鉴定、病原显微镜观察、血清学、DNA-DNA杂交和PCR检测等方法。     

柑橘黄龙病高光谱早期鉴别及病情分级

为实现柑橘黄龙病的早期、快速确诊,有效阻止病害蔓延,达到早期防治、保障柑橘生产的目的,该文研究基于高光谱成像的柑橘黄龙病早期无损检测及病情分级,并对多种预处理方法的建模结果进行探讨。试验获取370～1 000 nm健康、不同染病程度及缺锌共5类柑橘叶片的高光谱图像,用遥感图像处理平台(environment for visualizing images,ENVI)得到各类样本感兴趣区域的光谱反射率平均值。运用一阶微分、移动窗口拟和多项式平滑(savitzky-golay,SG)进行数据处理,结合偏最小二乘判别分析(partial least squares-discriminate analysis,PLS-DA)构建黄龙病的早期鉴别及病情分级模型。结果表明:建立的3个判别模型,验证集相关系数均不低于0.9548。其中,经SG平滑及一阶微分预处理所建立的模型分类效果最佳,总体预测准确率达96.4%,预测均方根误差0.1344。该研究为柑橘病害早期诊断和预警提供了新方法,也为黄龙病病害程度遥感监测提供了基础。     

Detection of ‘Candidatus Liberibacter asiaticus’ in citrus by concurrent tissue print-based qPCR and immunoassay

‘Candidatus Liberibacter asiaticus’ (CLas) is associated with the most destructive disease of citrus, huanglongbing (HLB). The most widely used methods for detection of CLas are PCR-based and require purification of DNA from plant samples. Elution of DNA from tissue prints made on nitrocellulose membranes followed by qPCR (TPE-qPCR) was compared to DNA extraction of plant tissue followed by PCR (X-PCR) by testing the same tissue samples. The former estimated a higher CLas population in tissue prints than the latter (t-test; P = 0.009). All extracts prepared for TPE-qPCR throughout the experiment were also tested by conventional PCR and 80.8% were identified as positive. A similar set of stem and petiole tissue samples was tested by TPE-qPCR and immunoassay. Although the detection rate by TPE-qPCR was higher than by immunoassay, about 6% of tissue prints were positive by immunoassay but not by TPE-qPCR. Thus, a higher detection rate would be achieved by combining TPE-qPCR with immunoassay. Significant differences were observed in the performance of nitrocellulose membranes from different manufacturers in these assays. Immunotissue prints showed that the spatial distribution pattern of CLas infection varied widely from one sample to another, but the patterns were highly correlated among serial sections from the same sample, suggesting that CLas preferentially colonizes adjacent phloem cells in a vertical rather than horizontal direction.     

赣南脐橙产区应用有人直升机防治柑橘木虱 控制柑橘黄龙病初报

防治柑橘木虱是遏制柑橘黄龙病扩散的关键措施之一,应用有人直升机防治柑橘木虱目前还没有相关文献报道。本文介绍了赣南脐橙产区在嫩梢期应用有人直升机防治柑橘木虱的做法及成效。结果表明：有人直升机施药雾化性能较好,雾滴附着率高,雾滴分布较均匀,14个处理607个雾滴检测样本平均雾滴密度13.33 粒/cm2,雾滴密度符合农业航空植保技术作业要求;各处理对柑橘木虱均有很好的防治效果,药后7 天,防效都达90%以上。有人直升机具有作业效率高、突击能力强、不同地形地貌适应性好等特点,能在短时间内大面积施药作业,对失管果园、隔离带和杂草上的木虱也能同时防治,解决了一家一户防治时间不统一的问题,可以大面积减少虫口基数,是目前柑橘黄龙病发生区可以借鉴应用的重要技术措施。提出了加快农药产品的研发和登记、防范发生次生灾害、完善防治技术及轮换用药避免产生抗药性等建议。     

Tissue‐print and squash real‐time PCR for direct detection of ‘Candidatus Liberibacter’ species in citrus plants and psyllid vectors

Huanglongbing (HLB) disease is seriously threatening and/or damaging the citrus industry worldwide. Accurate detection of the three species associated with HLB disease, ‘Candidatus Liberibacter asiaticus’, ‘Candidatus Liberibacter africanus’ and ‘Candidatus Liberibacter americanus’, is essential for the preventive control of the disease. Real‐time PCR is a useful tool for bacterial detection. However, nucleic acid purification steps limit the number of samples that can be processed by PCR. Universal detection of ‘Ca. Liberibacter’ species was achieved by direct tissue‐printing and spotting of plant leaf petiole extracts or squashing of individual psyllids onto paper or nylon membranes. Primers were designed and used with TaqMan chemistry for accurate detection of the bacterium in immobilized targets (prints of 10 overlapping leaf pedicels per tree, or squashed single vectors), by extraction with water and direct use for real‐time PCR. This simplified method was validated and could detect HLB‐liberibacters in 100% of leaves with symptoms and 59% of symptomless leaves collected from HLB‐infected trees. The use of direct assays as template showed good agreement with use of purified DNA (κ = 0·76 ± 0·052). The squash assay allowed detection of the bacterium in 40% of mature Diaphorina citri that fed on leaves of HLB‐infected trees with or without symptoms. A commercial ready‐made kit based on this technology showed 96% accuracy in intra‐laboratory performance studies. The simplified direct methods of sample preparation presented herein can be effectively adopted for use in rapid screening of HLB agents in extensive surveys, certification schemes or for epidemiological and research studies.     

柑橘花器和种子中黄龙病菌的定量分布及应用

为准确、快速测定感病柑橘花器和种子中黄龙病菌（Candidatus Liberibacter asiaticus,Las）的含量,比较了SYBR Green Ⅰ实时荧光定量PCR（SGI-qPCR）和单管双引物对TaqMan探针qPCR（STDP-qPCR）的检测灵敏度,并用STDP-qPCR法定量检测了感病沙田柚花器和种子中的Las。结果显示,STDP-qPCR检测灵敏度为1×10⁰拷贝/μL,比SGI-qPCR高100倍;花器中的雄蕊、花瓣、雌蕊和花粉等组织,以及种子的种皮和胚乳组织中均可检测到Las,但含量差异较大,其中种皮组织中Las含量最高,达到109 842个细胞/μg DNA,花粉中的Las含量最低,为308个细胞/μg DNA,所有种壳中均未检测到Las;基于雄蕊组织的黄龙病分子诊断准确率达93.8%。表明Las在感病柑橘花器和种子中呈不均匀分布,基于雄蕊组织的黄龙病诊断方法可辅助用于该病害的高通量检测。     

江西省吉安、抚州两地区柑橘黄龙病发生调查

2005年至2008年,对江西省吉安和抚州两地区共20个县、区柑橘黄龙病发生情况进行了实地调查和病样室内诊断,结果表明抚州地区目前尚无柑橘黄龙病发生,吉安地区的吉安、永新、新干、峡江、安福、吉水、水丰也无黄龙病发生,而吉安地区的遂川、万安、泰和3县则已发现了黄龙病。柑橘品种对黄龙病抗病性存在差异,椪柑最感病,而南丰蜜橘则抗病。