Monitoring for resistant populations of <Emphasis Type="BoldItalic">Xanthomonas citri</Emphasis> subsp. <Emphasis Type="Italic">citri</Emphasis> and epiphytic bacteria on citrus trees treated with copper or streptomycin using a new semi-selective medium

Streptomycin has been tested as an alternative to copper bactericides, which are routinely used for the control of citrus canker (Xanthomonas citri subsp. citri, Xcc) in citrus producing areas where the disease is endemic. A major concern is that excessive use of copper as a bactericide may lead to development of copper-resistant strains of Xcc. In this study, we developed a semi-selective medium to recover copper or streptomycin-resistant strains of Xcc from citrus leaves. The newly developed semi-selective medium was used to monitor the effect of a 21-day-interval copper or streptomycin spray program on Xcc for three consecutive seasons and on citrus epiphytic bacterial populations for two seasons in a commercial grapefruit grove. Although, no copper- or streptomycin-resistant strains of Xcc were isolated after three seasons, we observed a significant increase over time in the frequency of citrus epiphytic bacteria resistant to these chemicals. Overall, the proportion of epiphytic bacteria resistant to streptomycin on treated and untreated leaves was proportionally lower than the copper-resistant bacterial population. When application of each bactericide was suspended for the season, the proportion of bactericide-resistant bacteria in the epiphytic population decreased to that of the non-treated bacterial population. Availability of an alternative bactericide, such as streptomycin, to integrate into a copper-based program would reduce the amount of each bactericide sprayed in citrus orchards and possibly lower the selection pressure for bacterial resistance to these chemicals.     

Efficacy of five selected acaricides against Tetranychus urticae (Acari: Tetranychidae) and their side effects on relevant natural enemies occurring in citrus orchards

BACKGROUND: Three groups of natural enemies are fundamental in citrus IPM in Spain: coccinellid and phytoseiid predators and hymenopteran parasitoids. Tetranychus urticae Koch is an important pest affecting citrus, for which biological control has not yet been achieved; therefore, acaricides are commonly used to control it. The goal of this study was to measure the efficacy of different acaricides on this mite and their side effects on three natural enemies relevant for citrus (Cryptolaemus montrouzieri Mulsant, Neoseiulus californicus McGregor and Aphidius colemani Viereck).RESULTS: Some products proved highly effective against T. urticae and harmless to A. colemani (mineral oil, tebufenpyrad, clofentezine and fenazaquin). However, almost all products tested were slightly harmful for both the predators considered. Fenazaquin was even moderately harmful for N. californicus. CONCLUSION: Further studies, like that presented here, are necessary to gain a better understanding of integrating biological and chemical controls. When considering both efficacy and side effects on beneficial arthropods, the best options would seem to be mineral oil, tebufenpyrad and clofentezine. However, it is urgent to complete testing of the side effects of the acaricides used in citrus. This question is crucial if the fact that two recently introduced Tetranychidae are being controlled in citrus by chemical means exclusively is considered.     

不同药剂防治方案对某些柑桔病虫害的防治效果及成本分析

1997年7月至2000年6月在浙江黄岩进行了不同药剂防治方案对某些柑桔病虫害的防效及成本的比较试验。结果显示，与果农常规的以使用化学合成农药为主的防治方案相比，采用以使用机油乳剂和铜制剂为主的防治方案既能使柑桔病虫害得到有效的控制，又使果园生态得到改善、天敌群落密度及其对害虫的自然控制力得到恢复，进而使害虫得到可持续的控制。实施该防治方案的初期成本可能会稍高于常规防治方案，但持续实施后，天敌群落密度增加，对害虫的自然控制力提高，需要用药的次数减少，一年后其防治费用会降至常规防治方案之下。     

Implementation of integrated pest management in Israel

Supervised control programs were initiated by the Extension Service in the deciduous orchards of Upper Galilee and the Golan almost 20 years ago. The integrated pest management (IPM) project on fruit crops and vines, launched as a systematic state-wide program in 1991, covered 23% of the total acreage at the end of 1996. The program has reached a critical mass and generates a steady demand for this new kind of advisory service. The project has set the right pattern for intensive and continuous collaboration among research, extension and grower. The program has been successful in reaching out to growers with the help of a newly formed group of local and regional pest scouts; the field-level implementation is the responsibility of the extension system. A reduction of approximately 30% in the use of pesticides has been achieved. The project prepares the ground for environment-friendly and sustainable cropping systems, generating produce competitive on both the local as well as foreign markets. The program on indoor vegetables, flowers, herbs and spices initiated in 1992, had to address first the problem of the sweetpotato whitefly. The field program methodology relies on the establishment of model farms and plots. The model plots are used to examine supervised control scenarios which could, in turn, be diffused to all growers. A 30-50% reduction in the use of pesticides was achieved on the model farms. The program represents an integration of supervised control, fully fledged IPM, and biological control practices. The program on corn and cotton covers the entire acreage under these two crops. The cotton program is supported by an integrated resistance management component. Three area-wide pest management programs were initiated: in the Arava and Bet She’ an valleys, and in the Golan.     

Management strategies of mealybug pests of citrus in mediterranean countries

Six mealybug species have been reported as citrus pests in the Mediterranean Basin: the citrus mealybugPlanococcus citri (Risso), the citriculus mealybugPseudococcus cryptus Hempel, the longtailed mealybugPseudococcus longispinus (Targioni-Tozzetti), the citrophilus mealybugPseudococcus calceolariae (Maskell), the obscure mealybugPseudococcus viburni (Signoret) and the spherical mealybugNipaecoccus viridis (Newstead). Some of these species,e.g. N. viridis, have recently been introduced into the region and are still spreading. Mealybugs are usually occasional or minor pests of citrus, but some species can reach key pest status. Mealybug management strategies in citrus have been based mostly on classical biological control and, to a lesser extent, on augmentative releases. However, chemical control is widely used, mainly because of the poor adaptation of the principal natural enemies to the climatic conditions of the Mediterranean. The application of pheromones is still restricted to monitoring the citrus mealybug, whose sex pheromone is commercially available. Mass trapping and mating disruption should be considered for possible use in IPM programs as an alternative method to supplementary chemical treatments. Enhancement of biological control through management of ant populations is another promising tactic for control of mealybugs. Strategies for managing mealybug pests of citrus, and possible levels of integration of different tactics according to the pest status, are discussed. http://www.phytoparasitica.org posting Oct. 3, 2004.     

黑刺粉虱的发生、为害及其生物防治国内研究概况

黑刺粉虱Aleurocanthus spiniferus为茶园和柑桔园为害严重的粉虱种类之一。本文概述了黑刺粉虱在国内分布、寄主种类、发生与为害等,探讨了近年来生物防治在控制黑刺粉虱为害中的作用,包括寄生性天敌、捕食天敌及昆虫病原性真菌等的利用,以期为黑刺粉虱的综合治理提供参考。     

Fifty years of the integrated control concept: moving the model and implementation forward in Arizona

Fifty years ago, Stern, Smith, van den Bosch and Hagen outlined a simple but sophisticated idea of pest control predicated on the complementary action of chemical and biological control. This integrated control concept has since been a driving force and conceptual foundation for all integrated pest management (IPM) programs. The four basic elements include thresholds for determining the need for control, sampling to determine critical densities, understanding and conserving the biological control capacity in the system and the use of selective insecticides or selective application methods, when needed, to augment biological control. Here we detail the development, evolution, validation and implementation of an integrated control (IC) program for whitefly, Bemisia tabaci (Genn.), in the Arizona cotton system that provides a rare example of the vision of Stern and his colleagues. Economic thresholds derived from research‐based economic injury levels were developed and integrated with rapid and accurate sampling plans into validated decision tools widely adopted by consultants and growers. Extensive research that measured the interplay among pest population dynamics, biological control by indigenous natural enemies and selective insecticides using community ordination methods, predator:prey ratios, predator exclusion and demography validated the critical complementary roles played by chemical and biological control. The term ‘bioresidual’ was coined to describe the extended environmental resistance from biological control and other forces possible when selective insecticides are deployed. The tangible benefits have been a 70% reduction in foliar insecticides, a >$200 million saving in control costs and yield, along with enhanced utilization of ecosystem services over the last 14 years. Published in 2009 by John Wiley & Sons, Ltd.     

“以螨治螨”生防技术在南丰蜜桔上的应用

2005-2007年,在南丰蜜桔上建立了以人工释放捕食螨控制柑桔害螨为核心,辅以配套的农业、物理和药剂防治措施的桔园虫害控制技术体系。试验证明该技术对防治以柑桔害螨为主的柑桔虫害效果显著。6月中旬以后,生防区红蜘蛛平均虫口密度仅为0.15头/叶,其他主要害虫如粉虱、蚧虫和蚜虫等的发生量均显著少于化防区和对照区。随着该技术的示范和推广,已逐渐展现出巨大的经济效益,每亩可节本增效600元以上,累计增加经济效益达900万元以上。同时提高了桔农素质,提升了生产水平;减少施用有毒农药60%以上,改善了生态环境,进而创造了良好的社会效益和生态效益,为加快推动南丰蜜桔无公害标准化生产进程,保障南丰蜜桔产业的可持续发展提供了技术支撑。     

Impact of some alternative methods to chemical control in controlling aphids (Hemiptera: Sternorrhyncha) and their side effects on natural enemies on young Moroccan citrus groves

Aphid control in Moroccan citrus orchards is based mainly on carbamate and neonicotinoid sprays, especially methomyl and imidacloprid. The extensive use of these insecticides may have side effects on natural enemies and environment quality and raises human health concerns. This research aimed to assess the control of aphids with insecticidal soap, kaolin and augmentative biological control using the indigenous predator Adalia decempunctata L. (Coleoptera: Coccinellidae). The insecticides were applied and the predators were released in April 2009 and 2010. Under field experimentation, the methomyl and imidacloprid foliar pulverization were very effective against aphids. In contrast, the insecticidal soap and kaolin application were less efficient while A. decempunctata adults were effective only in the first week after release. The side effects on beneficial insects were also assessed and discussed. The possibility of employing A. decempunctata in an integrated pest management package in citrus groves is discussed in relation to effectiveness and side effects on beneficial arthropods.     

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?     

应用楝科植物防治柑桔害虫试验

本文应用楝科植物(印楝、川楝、苦楝)种籽油及其抽提物对柑桔木虱及其他害虫进行一系列的忌避拒食及触杀作用试验,证明印楝油有明显的忌避及拒食作用。印楝油对柑桔潜叶蛾有良好的防效。印楝、川楝及苦楝油对柑桔红蜘蛛也有较强的触杀作用。应用楝科植物杀虫剂可兼治几种害虫,对人畜安全,不污染环境,不会引起抗药性的产生,而且对害虫天敌也比较安全。     

Bacteria from the citrus phylloplane can disrupt cell–cell signalling in Xanthomonas citri and reduce citrus canker disease severity

Xanthomonas citri subsp. citri (Xcc) is the causal agent of citrus canker, a disease that affects almost all types of citrus crops. Production of particular Xcc pathogenicity factors is controlled by a gene cluster rpf, which encodes elements of a cell–cell communication system called quorum sensing (QS), mediated by molecules of the diffusible signal factor (DSF) family. Interference with cell–cell signalling, also termed quorum quenching, either by signal degradation or over‐production, has been suggested as a strategy to control bacterial disease. In this study, three bacterial strains were isolated from citrus leaves that displayed the ability to disrupt QS signalling in Xcc. Pathogenicity assays in sweet orange (Citrus sinensis) showed that bacteria of the genera Pseudomonas and Bacillus also have a strong ability to reduce the severity of citrus canker disease. These effects were associated with alteration in bacterial attachment and biofilm formation, factors that are known to contribute to Xcc virulence. These quorum‐quenching bacteria may represent a highly valuable tool in the process of biological control and offer an alternative to the traditional copper treatment currently used to treat citrus canker disease.     

Precautions for and experiences with introduction of exotic biological control agents into the former USSR1

The experience of introducing more than 120 species of exotic biological control agents for use against more than 40 species of pests during 70 years in the countries of the former USSR is analysed. The examples of biological protection of citrus orchards and some other programmes using biological control agents are described in more detail. The precautionary measures elaborated for these programmes consist of: (1) the prohibition of use by insufficiently qualified persons or non-State organizations; (2) phytosanitary procedures preventing the spread of quarantine pests; (3) elimination from the biological control material of any hyperparasites, diseases or other accidentally introduced organisms under adequate quarantine conditions; (4) investigations at the place of release of the biological control agent into the environment.     

柑桔黄龙病综合防治研究

实施以采用无病种苗和田间防疫为中心的柑桔黄龙病综合防治技术,在新区两项措施并举,现树龄已９￣１４年生,仍然健康高产,每ｈｍ＾２产量达３２６００ｋｇ,田间保持既无黄龙病株,亦无柑桔木虱,对病区仅施行“田间防疫”,也能压低田间病株率和控制田间传染,维持果园效益。     

柑桔溃疡病综合防治研究

1985-1989年研究结果表明:14%胶氨铜水剂是目前防治柑桔溃疡病较理想的杀菌剂,效果略超过常规农药波尔多液;溃疡病药剂防治适期是春、夏、秋梢的梢长分别为4-5、6-7、5-6cm时,以及果实横径为0.8-1.0、1.8-2.0、2.8~3.0cm时。重病园用单一防治措施无法奏效,综合防治可有效地降低发病程度,提高果实产量、品质及增加经济效益。     

Altitude,tree species and soil type are the main factors influencing the severity of <Emphasis Type="Italic">Phaeoramularia</Emphasis> leaf and fruit spot disease of citrus in the humid zones of Cameroon

In Cameroon and most countries of tropical Africa where Phaeoramularia leaf and fruit spot disease of citrus is reported, a total yield loss of 50–100% is common. For effective control of this disease, it is imperative to understand how it originates, and which factors contribute to its development. To this end, the environmental and biological characteristics of each tree from 39 sites located in 13 citrus production basins in the humid zones of Cameroon were collected by means of a survey. Information was collected by interviewing heads of households, and by visual inspection of trees and their environment. The independent variable was severity of the disease while the dependent variables were environmental and biological characteristics. Climatic characteristics varied from one basin to another. The 13 citrus production basins were regrouped in five categories based on disease severity. Altitude, tree species and soil type were the main factors influencing the disease severity. Thus the higher is the altitude, the more important is the disease severity. Also, disease severity increased with increasing number of grape fruit, orange and pummelo trees. However, disease severity was lower on trees growing on volcanic soils as compared with the other soil types. Further analysis of these factors could lead to the development of a risk assessment model for Phaeoramularia leaf and fruit spot of citrus.     

Can an integrated management approach provide a basis for long-term prevention of weed dominance in Australian pasture systems?

Broad-leaved weeds in pasture, such as Carduus nutans, Onopordum spp. and Echium plantagineum are a major problem for graziers in southern Australia. Previous attempts to combat these weeds with a single technique have only resulted in short-term success. An approach to long-term control, combining biological control with different grazing and herbicide strategies, was evaluated in an integrated weed management (IWM) programme, in south-eastern Australia. This IWM study was one of the few that has focused on biological control agents. During the field trials, the impacts of grazing and herbicide treatments on the weed and biological control agents, as well as on pasture composition, were monitored. This paper concentrates on the part of the study that focuses on the role and importance of pasture composition as part of weed management. The main pasture components were monitored using botanal , a sampling technique for estimating species composition and pasture yield in the field. IWM is a long-term ecological approach and after 3 years, major trends were just becoming apparent. This study shows that pasture composition can be manipulated to increase productivity and sustainability. It demonstrates that broad-leaved weeds can be reduced when high level pasture background management and chemical control are combined.     

玳玳桔潜蛾发生规律与综合防治研究

玳玳是芸香科柑桔属的一种香料,大面积种植屡遭桔潜蛾严重为害。桔潜蛾在玳玳上1年发生11个世代,发生在秋梢期的第七至九代为主害代。秋梢受害率达52.1—100%,经济损失达24.9%以上。根据害虫和寄主各自生物学特性,采用以改变害虫生态条件为主,协调运用科学管梢、以肥调梢、保护利用天敌和药剂挑治等四项综防措施。经2600亩应用,梢叶产量提高65.4%,冠幅平均扩大34%,保梢效果达91%,三年企业直接获利10万余元。     

湖南丘陵桔园间种藿香蓟对桔树螨类和昆虫的影响

作者评价了湖南丘陵桔园间种藿香蓟对桔树螨类和昆虫的影响。桔园间种藿香蓟、免耕蓄草能改善桔园的小生境,提高桔园夏季相对湿度和冬季温度,降低夏季树冠和土壤温度,创造一个有利于天敌生存的良好环境;能提供钝绥螨的交替食料和栖息、产卵场所;能控制柑桔全爪螨的秋季为害,减轻柑桔全爪螨的春季为害和柑桔潜叶蛾的为害,但加重了柑桔花蕾蛆和天牛类害虫的为害。能提高树体的抗旱和抗寒能力,改善土壤结构,增加土壤肥力,提高柑桔品质和产量,降低防治费用。文中还评价了防治策略、灌溉方式和藿香蓟的长势等因素对间种藿香蓟控制柑桔全爪螨的作用。