An update on control of brown spot of pear

Brown spot of pear is a fungal disease producing high economical losses in several pear-growing areas in Europe. Fungicide applications during the growing period either at fixed schedule or delivered according to the BSPcast forecasting system are not enough to control the disease under favorable conditions. New strategies have been introduced to control the inoculum production using sanitation methods. These methods are based on combinations of leaf litter removal during winter and biological control agent applications during late winter, spring and summer. These practices reduce both the inoculum pressure and disease levels. Therefore, the resulting optimized disease management consists of a combination of sanitation methods applied during the whole year with chemical fungicides scheduled according to the BSPcast forecasting model during the vegetative period. It is expected that the control of brown spot could be further refined upon availability of rapid methods for inoculum potential analysis. However, this analysis is difficult due to the variability in pathogenicity within the pathogen population.     

Identification of Alternaria tenuissima causing brown leaf spot on Paris polyphylla var. chinensis in China

Severe brown leaf spot disease was observed on Paris polyphylla var. chinensis in Sichuan Province, China, in 2017 and 2018. The initial symptoms were many light‐brown small spots with necrotic centres, round or irregular in shape, becoming dark brown, gradually enlarging and eventually coalescing, causing extensive leaf senescence. A fungus was isolated from diseased leaves showing typical symptoms of brown leaf spot. The isolates were cultured on potato sucrose agar, and their morphological characteristics of the causal pathogen were observed under a light microscope. Pathogenicity tests revealed that this fungus was the causal pathogen of the disease. Molecular analyses of the sequences of the ribosomal DNA internal transcribed spacer (ITS) region, translation elongation factor 1‐alpha (TEF) and the RNA polymerase II second largest subunit (RBP2) gene were conducted to confirm the identity of the pathogen. The multi‐gene phylogeny indicated that the causal agent was Alternaria tenuissima. To our knowledge, this is the first report of A. tenuissima causing brown leaf sports on P. polyphylla var. chinensis in China.     

运用化学药剂防治红腹柄天牛

室内防治试验表明,在某些特定稀释浓度条件下,毒签塞孔法比注射法效果好,而混合杀虫剂又比单一试剂效率高。敌敌畏 杀灭菊酯1∶1毒签塞孔防治(用药量2 mL.株-1),杀虫效果达86.67%。在自流式树干注药法中,氧化乐果的防效最好,为81.67%。     

Enhancement of the citrus immune system provides effective resistance against Alternaria brown spot disease

In addition to basal defense mechanisms, plants are able to develop enhanced defense mechanisms such as induced resistance (IR) upon appropriate stimulation. We recently described the means by which several carboxylic acids protect Arabidopsis and tomato plants against fungi. In this work, we demonstrate the effectiveness of hexanoic acid (Hx) in the control of Alternaria brown spot (ABS) disease via enhancement of the immune system of Fortune mandarin.     

Studies on the seed-borne phases of dark leaf spot Alternaria brassicicola and grey leaf spot Alternaria brassicaeof brassicas

Tests in Britain on samples of basic and commercial Brassica oleracea seed between 1976 and 1978 showed that many lots were infected with Alternaria brassicicola. A. brassicae was uncommon in basic seed in these years and in commercial seed harvested in 1976 and 1977 but was frequent in seed harvested in 1978. Most affected seeds were contaminated by surface-borne spores and mycelium of A. brassicicola but many were internally infected by the fungus situated within the seed-coat and in some seeds in the embryo tissues. Superficial contamination by the fungus declined rapidly after 2 yr in cabbage seeds stored at 10 °C, 50% r.h. but internal infection persisted for up to 12 yr. In some samples, internal infection was commonly associated with small shrivelled seeds. Surface contaminated and internally infected seeds transmitted the disease but seedling infection was more closely correlated with the latter.     

核果和仁果褐腐病病原菌研究进展

核果和仁果类果品在我国果品生产和消费中占有重要地位.由链核盘菌属Monilinia几种真菌引起的褐腐病可导致枝枯和果实腐烂,造成严重的经济损失.其中部分种类还是一些国家或地区的检疫性病原物.近年来褐腐病病原菌的组成、名称和分布已有新的变化,对链核盘菌和褐腐病的研究也取得了许多新进展.本文概述了过去20年来国内外对核果和...     

Chemical control of Ornithonyssus sylviarum on caged layer hens

Manual application of aqueous solutions of malathion, carbaryl and permethrin controlled northern fowl mite, Ornithonyssus sylviarum Canestrini and Fanzago, on caged layer hens for at least 118 days. Azamethiphos sprayed manually provided acceptable control for a shorter period. Machine application, particularly of azamethiphos, but also malathion, provided lesser control. The addition of surfactant increased the wetting ability of the sprays but interfered with the efficacy of azamethiphos.     

杨树粒肩天牛幼虫林间化学防治试验

选用3种化学药剂应用不同的施药方法对杨树粒肩天牛幼虫进行林间药效试验,结果表明,采用虫道注射与毒签两种施药方法林间防治粒肩天牛幼虫都具有良好的防治效果,15d后防治效果达71.44～97.54%,可在生产中推广应用。     

药剂喷施饵木防治双条杉天牛成虫的试验

2007年3月在室内进行药效筛选试验,结果表明,阿维·毒、毒死蜱、高效氯氟氰菊酯3种药剂喷施侧柏饵木均能杀死双条杉天牛成虫,毒死蜱作用最快,5d完全死亡率达到94.7%。2008年3月选用高效氯氰菊酯、阿维菌素·毒死蜱、丙溴磷进行了野外试验,结果表明,3种不同药剂防治效果差异显著,同种药剂不同浓度之间防治效果差异不显著,高效氯氰菊酯2000倍液效果最好。喷施高效氯氰菊酯、阿维菌素·毒死蜱不影响饵木的诱集效果。丙溴磷对饵木引诱效果产生影响,其机制机值得得进一步探讨。     

Toxic effect of herbicides used for water hyacinth control on two insects released for its biological control in South Africa

The integrated control of water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae) has become necessary in South Africa, as biological control alone is perceived to be too slow in controlling the weed. In total, seven insect biological control agents have been released on water hyacinth in South Africa. At the same time, herbicides are applied by the water authorities in areas where the weed continues to be troublesome. This study investigated the assumption that the two control methods are compatible by testing the direct toxicity of a range of herbicide formulations and surfactants on two of the biological control agents released against water hyacinth, the weevil, Neochetina eichhorniae Warner (Coleoptera: Curculionidae) and the water hyacinth mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae). A number of the formulations used resulted in significant mortality of the mirid and the weevil. Products containing 2,4-D amine and diquat as active ingredients caused higher mortality of both agents (up to 80% for the mirid) than formulations containing glyphosate. Furthermore, when surfactants were added to enhance herbicide efficiency, it resulted in increased toxicity to the insects. We recommend that glyphosate formulations should be used in integrated control programmes, and that surfactants be avoided in order to reduce the toxic nature of spray formulations to the insect biological control agents released against water hyacinth.     

Chemical control of potato common scab disease under field conditions

The aim of this study was to evaluate certain fungicides against Streptomyces scabies (Thaxter), the main causal agent of common scab disease in potato and other crops, in vitro and in vivo. Fourteen isolates of S. scabies were isolated from naturally infected potato tubers showing common scab symptoms. All isolates were pathogenic to potato tubers and produced typical symptoms of common scab. Isolate (No. 11) caused highest disease index (DSI) followed by isolates 10, 8 and 5 (61.13%). Seven fungicides (Rizolex, Capitan, Moncut, Ridomil, Maxim, Topsin, and Oxyplus) were screened in vitro for their toxicity against the pathogen isolate (No. 11). Results showed that four of them (Rizolex, Capitan, Moncut, and Ridomil) exhibited inhibition zone ranging from 5.33 to 26.33?mm. Capitan, Ridomil, and Rizolex were able to reduce DSI under field condition but they varied in their effects. Capitan was the best fungicide which aids in the reduction of disease (33.8%) followed by Ridomil (31.5%) while Rizolex (21.2%) was the lowest one.     

The expression of a baculovirus-derived chitinase gene increased resistance of tobacco cultivars to brown spot (Alternaria alternata)

The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) chitinase gene coding region was amplified using the polymerase chain reaction, inserted into a plasmid (pROK‐2) and replicated in Escherichia coli XL1–blue. The recombinant plasmid was mobilised into Agrobacterium tumefaciens LBA 4404 and inoculated into tobacco leaf discs. The presence of the expressed chitinase in foliar tissue of kanamycin‐resistant plantlets of three Nicotiana tabacum cultivars (CF80, K326 and Xanthi‐nc) was inferred using immunoblotting, and enzyme activity was confirmed using a fluorometric assay. Confocal laser scanning microscopy with immunofluorescent staining of foliar sections from N. tabacum Xanthi‐nc expressing the viral chitinase indicated that the enzyme was restricted to the vascular tissue. Heliothis virescens larvae fed on leaf tissue expressing chitinase were not impaired either in their development to pupation or in their feeding behaviour, in comparision with their counterparts that had consumed similar amounts of untransformed tobacco leaf tissue. By contrast, when tobacco leaves were mechanically inoculated with Alternaria alternata, very few brown spots were observed at inoculation sites in chitinase‐expressing tissue, whereas large and spreading lesions formed in untransformed tobacco tissue. Of all lines that were transformed, as determined by kanamycin resistance, 59% had fewer symptoms of disease (smaller disease indices) than those for untransformed controls.     

Perspectives on the development of biological control agents in Africa

Concern over the impact of chemical pesticides on human health and the environment continues to stimulate the study of alternative, biological pest control agents (BCA). In Africa, use of BCA products is just emerging, primarily in the export sector where growers are using a mixture of products from new African companies and products imported from outside Africa. In contrast, although interest in BCA for use in domestic markets has been widely supported by development funding partners for many years, few products have become available to these growers. The limited uptake of BCA in Africa suggests there may be constraints and issues working against their wider implementation. Here, we focus on non-technical constraints and issues facing microbial BCA applied inundatively, but arguments extend to a greater or lesser degree to all BCA. The challenges to wider BCA availability could be overcome by: a more coherent approach to their regulation across the continent; support for BCA development that is based on evidence of need and applicability; and political advocacy to lobby for necessary resources being made available to all stakeholders.     

Chemical control on Nesokia indica (bandicoot rat) in pistachio orchards of Kerman province

The rodents are a series of mammalians that have a high regeneration power. Their population increases rapidly. These animals comprise important agricultural pests, especially in pistachio orchards. In recent years, there is an increase in rodent population in pistachio orchards, which leads to enormous damage to these orchards. In this study, the effects of different poisons (phostoxin, simag, zinc phosphide and klerat) in rat control were compared. Based on the tests conducted, it was concluded that the poisons simag and zinc phosphide were the best. Note: In Kerman province, Nesokia indica is the dominant species (Wilson DE, Reeder DM. 1993 Wilson, DE and Reeder, M. 1993. Mammal species of the world a taxonomic and geographic reference. , 2nd ed, Washington and London: Smithsonian Institution Press.  [Google Scholar]. Mammal species of the world a taxonomic and geographic reference. 2nd ed. Washington and London: Smithsonian Institution Press).     

Effectiveness of acibenzolar-S-methyl, fungicides and antibiotics for the control of brown eye spot, bacterial blight, brown leaf spot and coffee rust in coffee

This study was carried out to evaluate the potential of acibenzolar‐S‐methyl (ASM), combined or not combined with fungicides and antibiotics for the control of brown eye spot (Cercospora coffeicola) and bacterial blight (Pseudomonas syringae pv. garcae) in coffee seedlings, and ASM combined with conventional fungicide application schedules for the control of coffee rust (Hemileia vastatrix) and brown leaf spot (Phoma costarricencis) under field conditions in two coffee crops in the State of São Paulo, Brazil. ASM protected coffee seedlings against C. coffeicola when applied at the rates of 2.5 and 5 g of active ingredient per hectolitre of water (g a.i. hL^?1), providing 34–55% of disease control, and against bacterial blight, when applied at the rates of 2.5, 10 and 20 g a.i. hL^?1, with 38–57% of disease control. Tebuconazole (100 g a.i. hL^?1) and azoxystrobin (10 g a.i. hL^?1) showed the best results for brown eye spot control. Oxytetracycline + streptomycin, kasugamycin hydrochloride, oxytetracycline + metallic copper, copper oxychloride and mancozeb + copper oxychloride also controlled bacterial blight in levels similar to those shown by ASM. In the field experiments, all fungicide application schedules tested, cyproconazole (December, February, April), epoxiconazole (December, March), tetraconazole (December, February, April), cyproconazole (December, February) and azoxystrobin (January, March) were effective for coffee rust control and provided partial control of brown leaf spot. The results also showed that for all experiments, there was no synergistic effect of the combination of ASM with azoxystrobin, cyproconazole or cupric fungicides.     

Integrated Control of Sclerotium rolfsii on Groundnut in South Africa

Sclerotium rolfsii Sacc. causes disease of numerous crop plants worldwide, including groundnuts. Control of this pathogen is difficult as it produces sclerotia which overwinter in the soil to emerge as inoculum and cause disease the following season. Various chemical, biological and cultural control strategies have been suggested and implemented, some of which have reduced disease incidence in the field. No studies have yet been undertaken in South Africa to control this disease on groundnut, either chemically, biologically or by cultural practices. In this study, several strategies were investigated for the control of S. rolfsii on groundnuts. Difenoconazole was identified as a fungicide that could possibly be applied in combination with Trichoderma harzianum, a biological antagonist of S. rolfsii, above carbendazim and flusilazole, and chlorothalonil. Difenoconazole significantly reduced the growth rate of S. rolfsii but not of T. harzianum. The cultivation of infected fields with an inversion plough significantly reduced infection of groundnuts by S. rolfsii and also improved the quality of the produce, while yield was not increased. Lower plant density increased the incidence of disease in an infected field, and is therefore not considered to be a viable form of cultural control.     

First report of Alternaria sp. PMK1: causative agent of leaf spot disease on parthenium weed

Congress grass, Parthenium hysterophorus L. (Asteraceae, tribe Heliantheae), is an erect and much branched annual or ephemeral herb, known as a pest for environmental, medical and agricultural reasons. Survey of fungal pathogens of P. hysterophorus was conducted in Kurukshetra and its adjoining areas, Haryana, India. A leaf spot pathogen Alternaria sp. PMK1 was isolated. Koch's postulates were performed and proved that this isolate was pathogenic to this weed. This is the first report of this pathogen causing leaf spot on parthenium weed.     

Combination of Trichoderma harzianum endochitinase and a membrane-affecting fungicide on control of Alternaria leaf spot in transgenic broccoli plants

Progeny from transgenic broccoli (cv. Green Comet) expressing a Trichoderma harzianum endochitinase gene were used to assess the interaction between endochitinase and the fungicide Bayleton in the control of Alternaria brassicicola. In vitro assays have shown synergistic effects of endochitinase and fungicides on fungal pathogens. Our study examined the in planta effects of endochitinase and Bayleton, individually and in combination. Two month old transgenic and non-transgenic plants were sprayed with ED50 levels of Bayleton and/or inoculated with an A. brassicicola spore suspension. Disease levels in non-sprayed transgenic plants were not statistically different from sprayed transgenic plants nor from sprayed non-transgenic controls. Thus endochitinase-transgenic plants alone provided a significant reduction of disease severity, comparable to the protection by fungicide on non-transgenic plants. Comparison of the expected additive and observed effects revealed no synergism between endochitinase and Bayleton (at ED50 level), and usually less than an additive effect. Some transgenic lines sprayed with fungicide at doses higher than ED50 showed resistance similar to the non-sprayed transgenic lines, again suggesting no synergistic effect. Lack of synergism may be due to incomplete digestion of the cell wall by endochitinase, so that the effect of Bayleton at the cell membrane is not enhanced.     

昆诺阿藜链格孢叶斑病病原及其生物学特性

为明确昆诺阿藜链格孢叶斑病病原,在山西省昆诺阿藜种植区采集典型症状的标本分离病原菌,选择代表性菌株LGB-b和LGB-h对其形态学、分子生物学、致病性及生物学特性进行了研究。综合形态学和多基因系统发育(Alt a 1、endoPG 和OPA10-2)分析,确定昆诺阿藜链格孢叶斑病病原为Alternaria alternata。致病性测定发现接种6 d后病斑呈灰绿至黄绿色,表面具有灰棕至灰褐色霉层,周围具黄绿色晕圈,与田间症状基本一致。菌株LGB-b和LGB-h均可侵染昆诺阿藜、藜和台湾藜。菌株LGB-b菌丝生长的最适培养基为V8 蔬菜汁琼脂培养基(V8)、温度为25-30 ℃、水活度≥0.98、pH为6-7;分生孢子萌发的最适水活度≥0.98、pH为6-7。菌株LGB-h菌丝生长的最适培养基为马铃薯胡萝卜琼脂培养基(PCA)、温度为20-25 ℃、水活度≥0.98、pH为6-7;分生孢子萌发的最适水活度≥0.98、pH为7-8。