Effect of Candidatus Liberibacter asiaticus infection on susceptibility of Asian citrus psyllid, Diaphorina citri, to selected insecticides

BACKGROUND: In the present investigation, the effect of Candidatus Liberibacter asiaticus (Las), a bacterium considered to be responsible for causing huanglongbing (HLB) disease in citrus, on the physiology of its vector, the Asian citrus psyllid (ACP) Diaphorina citri Kuwayama, was determined. Specifically, the effects of Las infection on the susceptibility of ACP to selected insecticides were determined. Furthermore, total protein content and general esterase activity were quantified in Las‐infected and uninfected ACP to gain insight into the possible mechanism(s) responsible for altered susceptibility to insecticides owing to Las infection. RESULTS: LC₅₀ values were significantly lower in Las‐infected than in uninfected ACP adults for chlorpyrifos and spinetoram. Furthermore, there was a general trend towards lower LC₅₀ values for three other insecticides for Las‐infected ACP; however, the differences were not statistically significant. Total protein content (µg mL^?1) was significantly lower in Las‐infected (23.5 ± 1.3 in head + thorax; 27.7 ± 1.9 in abdomen) than in uninfected (29.7 ± 2.1 in head + thorax; 35.0 ± 2.3 in abdomen) ACP. Likewise, general esterase enzyme activity (nmol min^?1 mg^?1 protein) was significantly lower in Las‐infected (111.6 ± 4.5 in head + thorax; 109.5 ± 3.7 in abdomen) than in uninfected (135.9 ± 7.5 in head + thorax; 206.1 ± 23.7 in abdomen) ACP. CONCLUSION: Susceptibility of ACP to selected insecticides from five major chemistries was greater in Las‐infected than in uninfected ACP. The lower total protein content and reduced general esterase activity in Las‐infected than in uninfected ACP may partly explain the observed higher insecticide susceptibility of Las‐infected ACP. Copyright © 2010 Society of Chemical Industry     

Antifeedant and sublethal effects of imidacloprid on Asian citrus psyllid,Diaphorina citri

BACKGROUND: Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, transmits the causal bacteria of the devastating citrus disease huanglongbing (HLB). Because of the variation in spatial and temporal uptake and systemic distribution of imidacloprid applied to citrus trees and its degradation over time in citrus trees, ACP adults and nymphs are exposed to concentrations that may not cause immediate mortality but rather sublethal effects. The objective of this laboratory study was to determine the effects of sublethal concentrations of imidacloprid on ACP life stages. RESULTS: Feeding by ACP adults and nymphs on plants treated daily with a sublethal concentration (0.1 µg mL^?1) of imidacloprid significantly decreased adult longevity (8 days), fecundity (33%) and fertility (6%), as well as nymph survival (12%) and developmental rate compared with untreated controls. The magnitude of these negative effects was directly related to exposure duration and concentration. Furthermore, ACP adults that fed on citrus leaves treated systemically with lethal and sublethal concentrations of imidacloprid excreted significantly less honeydew (7–94%) compared with controls in a concentration‐dependent manner suggesting antifeedant activity of imidacloprid. CONCLUSIONS: Sublethal concentrations of imidacloprid negatively affect development, reproduction, survival and longevity of ACP, which likely contributes to population reductions over time. Also, reduced feeding by ACP adults on plants treated with sublethal concentrations of imidacloprid may potentially decrease the capacity of ACP to successfully acquire and transmit the HLB causal pathogen. Copyright © 2009 Society of Chemical Industry     

柑橘喷施叶面肥对柑橘木虱､柑橘潜叶蛾和炭疽病发生的影响

柑橘生产上叶面肥的使用很普遍?为了评估喷施叶面肥对柑橘新梢期的主要害虫柑橘木虱Diaphorina citri和柑橘潜叶蛾Phyllocnistis citrella发生?为害的影响, 本文分别在养虫笼和网室条件下调查了以上2种害虫对喷不同叶面肥(尿素?复合氨基酸和葡萄糖)砂糖橘苗木的选择和为害, 以及柑橘炭疽病发生情况?试验结果表明:从木虱成虫选择性和产卵两个方面来看, 不同喷施处理的砂糖橘对木虱的吸引作用表现为尿素>复合氨基酸>葡萄糖>清水对照, 其中尿素和复合氨基酸处理吸引作用显著高于对照?喷施3种叶面肥后潜叶蛾为害程度均显著高于对照, 以葡萄糖处理的为害率和受害指数最高?另外, 尿素和复合氨基酸处理苗木的柑橘炭疽病病叶率和病情指数显著高于对照, 复合氨基酸处理病叶率显著高于葡萄糖?说明喷尿素?复合氨基酸叶面肥对柑橘木虱有较强的吸引作用, 同时加重柑橘炭疽病?另外, 与对照相比, 喷施3种叶面肥均能加重潜叶蛾的为害, 尤其是葡萄糖?     

13种常用农药对柑橘木虱田间种群防治效果室内评价

柑橘木虱Diaphorina citri Kuwayama是黄龙病的传播媒介,快速、有效防治这种害虫是综合防控黄龙病的关键。目前,其防治措施主要依赖化学农药。为了了解化学农药对柑橘木虱的田间防治效果,本文以广东省博罗县柑橘木虱田间种群为测试对象,以华南农业大学昆虫生态研究室饲养的种群为敏感对照,室内测定了13种常用药剂推荐浓度对柑橘木虱的防治效果。结果表明,24 h后77.5%敌敌畏EC和5%啶虫脒EC对田间种群的效果最好,柑橘木虱死亡率分别为93.3%和90%,48 h后两种药剂处理的死亡率已达100%;48 h后,350 g/L吡虫啉SC处理的死亡率也达93.3%;72 h后,20%丁硫克百威EC、30%噻虫嗪SC、12%高氯·毒死蜱EC、45%毒死蜱EC、2.5%高效氯氟氰菊酯EW处理的死亡率也达90%以上。两个种群相比,所有药剂在相同时间对敏感种群的防治效果都高于田间种群。其中,用20%甲氰菊酯EC、30%噻虫嗪SC、45%毒死蜱EC、25 g/L联苯菊酯EC、99%矿物油EC等5种药剂处理,24 h后田间种群的校正死亡率显著低于敏感种群;48 h后除上述药剂外,4.5%高效氯氰菊酯ME处理的校正死亡率也显著低于敏感种群。72 h后,4.5%高效氯氰菊酯ME、25 g/L联苯菊酯EC、99%矿物油EC处理的校正死亡率依然显著低于敏感种群。说明田间种群对以上药剂的敏感性有不同程度的下降。此外发现,采用此测定方法22.4%螺虫乙酯SC对田间种群和敏感种群的防治效果均不理想。     

4种剂型噻虫胺对柑橘木虱的田间防治效果

2018年-2019年,采用田间小区试验评价了噻虫胺4种剂型(30％悬浮剂、18％包埋颗粒剂、13.5％壳聚糖微球和0.5％颗粒剂)及2种施用方式(喷雾和沟施)对柑橘木虱的防治效果.结果 表明:叶面喷施30％噻虫胺悬浮剂60 mg/kg处理对幼年树及成年树上柑橘木虱的控制效果好且持效期约30 d,而药后46～96 d的...     

基于MaxEnt模型的柑橘木虱在西南地区潜在分布模拟

本研究应用生态位软件MaxEnt和地理信息系统软件ArcGIS预测柑橘木虱在西南地区的潜在地理分布范围,筛选影响柑橘木虱分布的关键变量。结果表明柑橘木虱在西南地区高适生区主要位于西藏东南部、四川中东部、重庆大部、贵州大部和云南中北部,总面积为52.03万km 2,占西南地区总面积的23.89%。影响柑橘木虱分布的关键变量为最冷月最低温度、最冷季度平均温度、最湿季度降水量、最暖季度降水量、最暖季度平均温度和最暖月最高温度。本研究不仅模拟了柑橘木虱在西南地区的潜在地理分布,更为该虫的分布与环境变量之间关系的研究提供了理论参考。     

Effects of pymetrozine, an antifeedant of Hemiptera, on Asian citrus psyllid, Diaphorina citri, feeding behavior, survival and transmission of Candidatus Liberibacter asiaticus

BACKGROUND: Vector‐borne plant disease management can be enhanced by deployment of antifeedants in addition to the use of broad‐spectrum neurotoxic insecticides. The effects of pymetrozine on Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, feeding behaviour, survival and transmission of Candidatus Liberibacter asiaticus (Las), the presumed causal pathogen of huanglongbing, were investigated. RESULTS: Pymetrozine applied at 52 and 104 µg mL^?1 to citrus plants [Swingle citrumelo (X Citroncirus webberi Ingram and Moore)] modified the feeding behavior of ACP and increased the amount of time spent performing non‐penetration behaviors while decreasing the time spent performing ingestion behaviors compared with the controls 1 day after treatment. However, the antifeedant effect of pymetrozine subsided 5 days after application. Pymetrozine reduced the survival of both adults and nymphs on treated plants compared with the control. However, it had a greater impact on survival of nymphs than on survival of adults. Pymetrozine applied at 52 and 104 µg mL^?1 on Las‐infected ‘Valencia’ sweet orange plants [Citrus sinensis L. (Osbeck)] reduced acquisition (12 and 21% respectively) and transmission (11 and 18% respectively) of Las by feeding ACP adults compared with the controls; however, these reductions were not statistically significant. CONCLUSIONS: Pymetrozine exhibited moderate antifeedant effects by modifying the feeding behavior of ACP adults with short residual activity. The impact of pymetrozine on survival of nymphs was greater than on adults at the higher concentrations tested. Pymetrozine also reduced the acquisition and transmission of Las by feeding ACP adults up to 21 and 18%, respectively, compared with untreated controls. Copyright © 2010 Society of Chemical Industry     

Toxicity of systemic neonicotinoid insecticides to avocado thrips in nursery avocado trees

The efficacies of four systemic neonicotinoid insecticides applied to potted avocado trees at manufacturer-recommended rates were assessed against the avocado thrips, Scirtothrips perseae Nakahara. At the time of treatment, fully expanded first-flush young leaves were tagged for identification, and a proportion of these leaves was used in bioassays with second-instar thrips. At 7 weeks post-treatment, a second flush of leaves had fully expanded on the trees, and these leaves were included in additional bioassays comparing avocado thrips mortality on both first- and second-flush leaves. In bioassays with first-flush leaves, imidacloprid (273 mg AI pot(-1)) was the most effective insecticide, providing at least 70% mortality of thrips for 14 weeks. Thiamethoxam (137 mg AI pot(-1)), clothianidin (109 mg AI pot(-1)) and dinotefuran (241 mg AI pot(-1)) provided good control in bioassays that were conducted within 4 weeks of treatment, but thereafter their efficacies were inconsistent. In bioassays with second-flush leaves, imidacloprid provided at least 70% mortality up to 9 weeks after the insecticide application. Thereafter, mortality declined to 30% or lower. Bioassays with second-flush leaves collected from trees treated with thiamethoxam, clothianidin and dinotefuran resulted in unacceptably low thrips mortality. Monitoring of imidacloprid and thiamethoxam residues by ELISA showed that the greater persistence of imidacloprid in both first and second leaf flushes was due to a steadier uptake of this material. Although thiamethoxam residues rose quickly within the first leaf flush, levels had already begun to dissipate by the time the second leaf flush had started to develop.     

Effect of pyriproxyfen,a juvenile hormone mimic,on egg hatch,nymph development,adult emergence and reproduction of the Asian citrus psyllid,Diaphorina citri Kuwayama

BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is a vector of bacteria presumably responsible for huanglongbing (HLB) disease in citrus. In this laboratory study, an investigation was made of the activity of pyriproxyfen, a juvenile hormone mimic, on ACP eggs, nymphs and adults to evaluate its potential as a biorational insecticide for inclusion in an integrated pest management (IPM) program for ACP. RESULTS: Irrespective of egg age, timing or method of treatment, a significantly lower percentage of eggs (5–29%) hatched after exposure to 64 and 128 µg mL^?1 of pyriproxyfen. Only 0–36% of early instars (first, second and third) and 25–74% of late instars (fourth and fifth) survived to adults following exposure to 16, 32 and 64 µg mL^?1 of pyriproxyfen. However, 15–20% of adults that emerged following treatment as late instars exhibited morphological abnormalities. Furthermore, pyriproxyfen adversely affected reproduction (fecundity and fertility) of adults that emerged from treated fifth instars or that were treated topically with 0.04 µg as adults. CONCLUSIONS: Application of pyriproxyfen at 64 µg mL^?1 resulted in greater inhibition of egg hatch and suppression of adult emergence compared with lower rates. Pyriproxyfen also markedly reduced female fecundity and egg viability for adults that were exposed either as fifth instars or as newly emerged adults. The ovicidal, larvicidal and reproductive effects against ACP suggest that pyriproxyfen is suitable for integration into an IPM program for ACP. Copyright © 2009 Society of Chemical Industry     

Rate, placement and timing of aldicarb applications to control Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), in oranges

BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a cosmopolitan insect pest of citrus and vectors the bacterium Candidatus Liberibacter asiaticus, a suspected causal organism of citrus greening or ‘huanglongbing’ disease. Aldicarb 150 g kg^?1 GR (Temik^® 15 G) was evaluated at three rates, two placements and three timings for ACP control in orange trees. RESULTS: Application of aldicarb at 5.6, 2.8 and 1.4 kg AI ha^?1 in March 2006 reduced adults by 58–66%, 45–46% and 25–37% respectively compared with untreated controls in two separate trials. No difference was observed in placement (one versus two sides of the tree) or tree size (8 years old versus 12 years old). Application at 5.6 kg ha^?1 in January 2007 reduced adults by 86% and shoot infestation by 77% in spring, and was generally better than the November and especially February applications. Even more striking results were evident on adults caged on treated plants for 25 days in March. Spiders and ladybeetles were equally abundant in treated and untreated trees. CONCLUSION: Aldicarb application at 5.6 kg ha^?1 to the bed side of mature citrus trees 2–3 months before spring growth can suppress ACP through spring without a direct effect on principal psyllid natural enemies. Copyright © 2008 Society of Chemical Industry     

7种挥发性化合物对柑橘木虱引诱效果的评价

柑橘黄龙病对全球的柑橘产业造成了严重的经济损失,其传播媒介主要为柑橘木虱。在前期研究中利用柑橘木虱对4种芸香科植物的取食偏好结合代谢组学分析筛选出一批可能对柑橘木虱具有引诱效果的挥发性化合物,本研究鉴定了邻氨基苯甲酸甲酯、癸酸、正辛醇、左旋香芹酮、2-环己烯酮、反式-1,2-环己二醇、吡嗪等7种挥发性化合物在0、0.1%、1%、10%4个浓度和10、20、30、40、50、60 min 6个持续时间下对柑橘木虱的引诱效果,并比较了其中5种脂溶性挥发物在各自最优浓度下的引诱效果。试验结果表明,7种挥发物对柑橘木虱都有引诱效果,但是引诱效果与挥发物浓度及持续时间有关。吡嗪、左旋香芹酮、正辛醇、2-环己烯酮、癸酸、邻氨基苯甲酸甲酯和反式-1,2-环己二醇的最佳引诱浓度分别为0.1%、1%、1%、1%、10%、10%、10%。六臂嗅觉仪试验结果显示5种脂溶性挥发物中1%左旋香芹酮的引诱效果高于10%癸酸、10%邻氨基苯甲酸甲酯、1%2-环己烯酮、1%正辛醇及对照(矿物油),但与其他4种挥发物没有显著差异。研究结果可为柑橘木虱引诱剂的开发提供参考,促进柑橘黄龙病的绿色防控。     

柑橘木虱防控药剂筛选及矿物油对其增效作用评价

为了筛选柑橘木虱高效防控药剂,提高药剂防治效果,本文探索了 10种杀虫剂对柑橘木虱的田间防效及矿物油对杀虫剂的增效作用.结果表明:对柑橘木虱成虫,22％噻虫·高氯氟悬乳剂(SE)、70％吡虫啉可湿性粉剂(WP)、6％联菊·啶虫脒微乳剂(ME)和5％高效氯氟氰菊酯ME的速效性好,药后1 d防效94.61％～100％;22...