Evaluation of strobilurins,acibenzolar and other chemicals,alone and in spray programs for the control of yellow Sigatoka leaf spot (Mycosphaerella musicola) of bananas in far northern Queensland,Australia

Abstract

Several chemicals including the strobilurins (trifloxystrobin, azoxystrobin, pyraclostrobin and DPX KZ 165), a plant activator (acibenzolar), the triazoles (propiconazole, tebuconazole, epoxiconazole, fenbuconazole and JAU 6475) and tridemorph, spiroxamine, pyrimethanil, fenarimol and various formulations of mancozeb were evaluated in three field experiments in northern Queensland, Australia for control of yellow Sigatoka of banana (caused by Mycosphaerella musicola). In all experiments, the strobilurins used alone or in spray programs with mancozeb and acibenzolar were as effective or better than the industry standards mancozeb and propiconazole. Acibenzolar used in spray programs with mancozeb significantly improved the control of Sigatoka compared to mancozeb alone. The triazoles, epoxiconazole, fenbuconazole and JAU 6476 used alone and tebuconazole in a spray program with mancozeb were as effective as the industry standard propiconazole. Tridemorph, pyrimethanil and spiroxamine were as effective as the industry standard mancozeb, and fenarimol failed to effectively control the disease. In 2004, trifloxystrobin, pyraclostrobin and epoxiconazole were registered for control of yellow Sigatoka of banana.     

香蕉褐缘灰斑病菌检测技术研究进展

香蕉褐缘灰斑病严重影响香蕉产量和品质,是香蕉生产上的重要生物灾害之一.香蕉褐缘灰斑病的早期诊断、检疫及防治的重要基础与前提是建立快速、灵敏的检测技术,从而准确及时鉴定出病原菌种类.本文介绍了香蕉褐缘灰斑病菌的种类和分类,概述了国内外香蕉褐缘灰斑病菌检测方法的研究进展,总结和归纳了传统、血清学、DNA指纹图谱、常规PCR...     

Relationship between the Spray Droplet Density of Two Protectant Fungicides and the Germination of Mycosphaerella fijiensis Ascospores on Banana Leaf Surfaces

The effect of fungicide spray droplet density (droplet cm^-2), droplet size, and proximity of the spray droplet deposit to fungal spores was investigated with Mycosphaerella fijiensis ascospores on the banana (Musa AAA) leaf surface for two contact fungicides: chlorothalonil and mancozeb. When droplet size was maintained at a volume median diameter (VMD) of 250 μm while total spray volume per hectare changed, M. fijiensis ascospore germination on the leaf surface fell below 1% for both fungicides at a droplet deposit density of 30 droplet cm^-2. At a droplet deposit density of 50 droplet cm^-2, no ascospores germinated in either fungicide treatment. When both droplet size and droplet cm^-2 varied while spray volume was fixed at 20 litre ha^-1, ascospore germination reached 0% at 10 droplet cm^-2 (VMD=602 μm) for both fungicides. At lower droplet densities (2–5 droplet cm^-2 VMD=989 μm and 804 μm respectively), ascospore germination on the mancozeb-treated leaves was significantly lower than on the chlorothalonil-treated leaves. The zone of inhibition surrounding a fungicide droplet deposit (VMD=250 μm) on the leaf surface was estimated to extend 1·02 mm beyond the visible edge of the spray droplet deposit for chlorothalonil and 1·29 mm for mancozeb. The efficacy of fungicide spray droplet deposit densities which are lower than currently recommended for low-volume, aerial applications of protectant fungicides was confirmed in an analysis of leaf samples recovered after commercial applications in a banana plantation. Calibrating agricultural spray aircraft to deliver fungicide spray droplets with a mean droplet deposit density of 30 droplet cm^-2 and a VMD between 300 and 400 μm will probably reduce spray drift, increase deposition efficiency on crop foliage, and enhance disease control compared to aircraft calibrated to spray finer droplets. © 1997 SCI.     

Efficacy and phytotoxicity of multiple petroleum oil sprays on sweet orange (Citrus sinensis (L.)) and pummelo (C. grandis (L.)) in Southern China

The efficacy of pest control of three different oil formulations in multiple low-concentration spray programmes on sweet orange and pummelo were compared with unsprayed and normal farmer-treatments over three years. Phytotoxicity of sprays was assessed in terms of fruit and leafdrop, fruityield and external fruitquality. Trees sprayed with any type of oil had lower pest numbers than unsprayed trees. On sweet orange, the heaviest oil was better than the normal farm practice at controlling chaff scale on fruit and red mite and whitefly on leaves. On pummelo it provided the best control of red mite on leaves. All three oils were as effective as the normal farm practice in control of rust mite on sweet orange fruit and leaves and red mite, rust mite and red scale on pummelo fruit. On sweet orange trees there was no evidence of phytotoxicity, and the external quality of fruit generally improved over time. On pummelo trees, oil sprays were unable to improve the external fruitquality. The number of pummelo per tree was reduced in three of the oil spray schedules in 1995 and one in 1996, but the total weight of fruit harvested per tree was unaffected.     

Distribution of Pseudocercospora species causing Sigatoka leaf diseases of banana in Uganda and Tanzania

Sigatoka leaf diseases are a major constraint to banana production. A survey was conducted in Tanzania and Uganda to assess the distribution of Pseudocercospora species and severity of Sigatoka leaf diseases. Pseudocercospora species were identified using species-specific primers. Sigatoka-like leaf diseases were observed in all farms and on all cultivars, but disease severity varied significantly (P < 0.001) between countries, districts/regions within countries, altitudinal ranges and banana cultivars. In all regions except Kilimanjaro, P. fijiensis, the causal agent of black Sigatoka, was the only pathogen associated with Sigatoka disease. Mycosphaerella musae was associated with Sigatoka-like symptoms in Kilimanjaro region. Black Sigatoka disease was more severe in Uganda, with a mean disease severity index (DSI) of 37.5%, than in Tanzania (DSI = 19.9%). In Uganda, black Sigatoka disease was equally severe in Luwero district (mean DSI = 40.4%) and Mbarara district (mean DSI = 37.9%). In Tanzania, black Sigatoka was most severe in Kagera region (mean DSI = 29.2%) and least in Mbeya region (mean DSI = 11.5%). Pseudocercospora fijiensis, the most devastating sigatoka pathogen, was detected at altitudes of up to 1877 m a.s.l. This range expansion of P. fijiensis, previously confined to altitudes lower than 1350 m a.s.l. in East Africa, is of concern, especially for smallholder banana farmers growing the susceptible East African Highland bananas (EAHB). Among the banana varieties sampled, the EAHB, FHIA hybrids and Mchare were the most susceptible. Here, the loss of resistance in Yangambi KM5, a banana variety previously resistant to P. fijiensis, is reported for the first time.     

Effects of adjuvants on the performance of a novel powdery mildew fungicide, 1-(4-chlorobenzyl)-4-phenylpiperidine

The effects of adjuvants on the performance of a dispersible concentrate formulation (DCI) of a novel powdery mildew fungicide, 1-(4-chlorobenzyl)-4-phenylpiperidine (I) were investigated. The method involved assessment, under glasshouse conditions, of the therapeutic (curative) control of infections of powdery mildew (Erysiphe graminis DC f.sp. hordei Marchal) on barley (Hordeum vulgare, L.) eight to nine days after spray application to plants that had been inoculated one day prior to spraying. The results from the first trial showed that marked improvements (∽five-fold) in the performance of DCI could be obtained by the spray tank addition of some types of surfactant adjuvants and a series of further trials investigating a wide range of adjuvants was conducted. Nonylphenol, alkylamine and alcohol ethoxylates varying in mean ethylene oxide content between 5 and 20 moles were highly effective. There were indications that optimum performance enhancements were obtained with these surfactants containing between 5 and 10 moles ethylene oxide. Lower enhancements, sometimes only marginal, were obtained from trisiloxane, phosphate ester, propylene oxide, alkylamine-propylene oxide and castor oil ethoxylates and also alkyl polyglucoside biosurfactants. Negligible adjuvant enhancements were observed with emulsifiable paraffinic/naphthenic and rape seed oils, though slightly better enhancements were seen with an emulsifiable transmethylated rape seed oil and, interestingly, larger enhancements with an emulsifiable lipophilic alcohol. A final trial identified the alcohol ethoxylate, ‘Dobanol’ 91-6, as the most effective adjuvant and that its optimum application rate under glasshouse conditions was 250 g ha^-1. This information will be used to guide the design of field trials. © 1997 SCI     

Sensitivity of Mycosphaerella fijiensis, Causal Agent of Black Sigatoka of Banana, to Propiconazole

ABSTRACT One hundred monoascosporic isolates of Mycosphaerella fijiensis were collected in February and November 1994 from each of two banana (Musa spp.) plantations in Costa Rica. Locations at San Pablo and Coopecariari had been sprayed with propiconazole for the past 7 years to control black Sigatoka. One hundred monoascosporic isolates from a third location, San Carlos, with no history of fungicide use, also were tested for sensitivity to propiconazole. Fifty percent effective concentration (EC(50)) values were calculated for individual isolates by regressing the relative inhibition of colony growth against the natural logarithm of the fungicide concentration. In the February sample, the mean EC(50) values for San Pablo and Coopecariari populations were 0.06 and 0.05 mug a.i. ml(-1), respectively, which were not statistically different (P = 0.05). The mean EC(50) value of the population at San Carlos was 0.008 mug a.i. ml(-1), which was significantly lower (P = 0.001) than the mean EC(50) values obtained at San Pablo and Coopecariari. Frequency distributions of EC(50) values of isolates from the three populations collected in February showed that 80% of isolates from San Pablo and Coopecariari had EC(50) values greater than the highest EC(50) value from San Carlos, indicating a significant shift in reduced sensitivity to propiconazole. Isolates collected in November 1994, after eight treatments of propiconazole at San Pablo and Coopecariari, showed a significant increase in mean EC(50) values compared with the means observed in February. The high proportion of isolates with reduced sensitivity to propiconazole may account for the unsatisfactory control of black Sigatoka between 1992 and 1993 in the two banana plantations at San Pablo and Coopecariari.     

Sources of resistance to Pseudocercospora fijiensis,the cause of black Sigatoka in banana

Black Sigatoka, caused by Pseudocercospora fijiensis, is one of the most devastating diseases of banana. In commercial banana-growing systems, black Sigatoka is primarily managed by fungicides. This mode of disease management is not feasible for resource-limited smallholder farmers. Therefore, bananas resistant to P. fijiensis provide a practical solution for managing the disease, especially under smallholder farming systems. Most banana and plantain hybrids with resistance to P. fijiensis were developed using few sources of resistance, which include Calcutta 4 and Pisang Lilin. To broaden the pool of resistance sources to P. fijiensis, 95 banana accessions were evaluated under field conditions in Sendusu, Uganda. Eleven accessions were resistant to P. fijiensis. Black Sigatoka symptoms did not progress past Stage 2 (narrow brown streaks) in the diploid accessions Pahang (AA), Pisang KRA (AA), Malaccensis 0074 (AA), Long Tavoy (AA), M.A. Truncata (AA), Tani (BB), and Balbisiana (BB), a response similar to the resistant control Calcutta 4. These accessions are potential sources of P. fijiensis resistance and banana breeding programmes can use them to broaden the genetic base for resistance to P. fijiensis.     

Modelling black Sigatoka epidemics with seasonal dispersal of Mycosphaerella fijiensis ascospores over a banana plantation in the Ribeira Valley,São Paulo,Brazil

Knowing the patterns of Black Sigatoka development is essential to propose adequate disease management practices and evaluate their effects, which can be achieved through temporal analysis by integrating the evolving interactions of the pathosystem components, expressed by data on cumulative incidence and severity, and summarizing these data in a disease progress curve. Airborne spores are essential components for the progression of an epidemic in the context of a specific pathosystem. In this perspective, the spore count is an essential approach to assess and model an epidemic. This study evaluated the temporal dynamics of Black Sigatoka in a banana plantation in the Ribeira Valley, state of São Paulo, Brazil, while simultaneously performing a year-long evaluation of fungal spore aerobiology. The disease was intense during the rainy season, but the leaf emergence rate was high enough for quickly inverting the severity peak (between 169 and 197 days of evaluation). After that, the disease severity raised until reach the higher rates (around the score 7 out of 8). The disease progress curve of Black Sigatoka showed peaks of extreme severity, one in the rainy and another in the dry season, with high levels of ascospores in the air. The ascospore concentration and the severity of the disease correlated significantly on the same day of sampling and 15 days after ascospore sampling, corresponding to the average latency period of the disease in the region. The patterns of the disease progress curve in both peaks fitted the monomolecular model, with higher rates of disease increase in the rainy season.

     

Biodiesel as a carrier for pesticide formulations: a green chemistry approach

Abstract

This article discusses the present status and future scope of biodiesel as a carrier/diluents and alternative source to hazardous volatile organic compounds for liquid pesticide formulations. Development of user and environment-friendly liquid pesticide formulations for sustainable agriculture is the key focus of today’s agrochemical industries. Organic solvents play an important role in ensuring the efficient distribution and delivery of active ingredients (a.i.) during application of liquid pesticide formulations. Presently used petroleum-based solvents have many disadvantages such as low flash points, high volatility, flammability, phytotoxicity, and inhalation problems to users, etc. However, at present it seems that the use of renewable resources, especially plant oils, oils ester (fatty acids alkyl ester) like biodiesel has the capacity to replace the traditional petroleum-based solvents in liquid pesticide formulations with having sustainable characteristics like high flash point, safer storage, transportation and application. Biodiesel which is easily reproducible from waste cooking oil, waste edible oil, animal fat, etc. may be a suitable alternative green solvent for liquid pesticide formulations in the near future.     

应用RAPD标记技术鉴定香蕉褐缘灰斑病菌

采用Mycosphaerella fijiiensis和M.musicola的RAPD标记技术鉴定海南香蕉褐缘灰斑病菌,结果表明,分离自海南儋州、乐东、文昌、东方、澄迈、临高、琼海、昌江、琼山、三亚香蕉上的10个菌株均为M.fijiensis,引起香蕉黑叶条斑病。     

Management of banana leafspot (Sigatoka) disease in the Windward Islands∗

Abstract

The rugged terrain and large number of smallholdings are important factors in the control of yellow Sigatoka (Mycosphaerella musicola Mulder) in the Windward Islands. A network of reference points has been established in each island where the disease level is monitored by the simple method of Stover and Dickson (1970) and a new method that assesses early infections on the young leaves. This information is used to decide spray applications. The use of Piche evaporimeter data to forecast spray applications has been investigated and is considered useful. Several fungicides have been tested and tridemorph, biloxazol and imazalil found to give satisfactory control with a view to introducing a rotation programme to avoid the continued sole use of benzimidazole formulations and possible occurrence of tolerance.     

Pesticide usage on bananas with special references to fungicides

Bananas (including plantains) are widely grown throughout the tropics both for local consumption and for export. Pesticide usage is confined largely to the export crop because of its value and the susceptibility to diseases of varieties suitable for the export market. Most of the bananas grown for export are produced in Latin America and the Caribbean. Weed control with herbicides is particularly valuable in young banana plantations before a mature canopy is produced and when weeds compete with the shallow rooting system. Insecticides are used to control high populations of the banana weevil and may be used against fruit thrips. Nematicides are used extensively to control the banana root nematode and granular applications are now replacing soil injections. Fungicidal control of Sigatoka leaf diseases and fruit diseases has been practised for many years and is essential for the production of high quality, exportgrade fruit. Changes in the chemicals used and in application techniques have brought important benefits in recent years and genetic resistance is likely to play a large part in disease control in the future.     

The characteristics of mineral oils in relation to their inhibitory activity on the aphid transmission of potato virus Y

In greenhouse trials paraffinic mineral oils, characterized by a viscosity gravity constant (VGC) of 0.790–0.819, and with viscosities between 12 and 30 cSt at 37°C (66–150 SUS) proved to have the best aphid transmission inhibiting activity of potato virus Y to red peppers. The activity decreased rapidly with decreasing viscosities but only slowly with increasing values.Effective oils are further characterized by an unsulfonated residue (USR) of 95–100, indicating the near or total absence of aromatic structures, which are inactive and known to be phytotoxic. The paraffine-pourpoint should be below 0°C, indicating that n-paraffines do not form a very important part of the oil, since they are also inactive. Naphthenic structures seem equally inert, their percentage in the oil depending on the origin of the crude oil, because they cannot be separated from the paraffinic structures by refining procedures.Mineral oils which one commercialize for agricultural practice normally have an USR above 95 and a paraffine-pourpoint below 0°C. Therefore, the information on the classification, based on a VGC value and on the viscosity, is already sufficient to allow an evaluation of those oils of their suitability as inhibitor of the virus transmission by aphids.Samenvatting In kasproeven bleken minerale paraffine oliën, gekenmerkt door een VGC (viscositeits-dichtheidsconstante) van 0.790–0.819 en een viscositeit tussen 12 en 30 cSt bij 37°C (66–150 SUS) de beste werking te bezitten tegen de overdracht van aardappelvirus Y naar paprika door bladluizen. De werking verminderde snel bij afnemende viscositeiten beneden 12 cSt, slechts langzaam bij toenemende waarden boven 30 cSt.De minerale olie met de meest gunstige eigenschappen met betrekking tot verhindering van de virusoverdracht wordt verder nog gekenmerkt door een USR (nier-sulfoneerbare rest) van 95–100. Dit betekent het geheel of bijna geheel afwezig zijn van aromatische verbindingen, die bekend zijn om hun fytotoxische eigenschappen en bovendien niet werkzaam zijn. Het stollingspunt moet bij voorkeur onder 0°C liggen wat betekent dat n-paraffinen geen al te belangrijk bestanddeel van de olie vormen, aangezien deze eveneens onwerkzaam zijn. Naphthenische structuren bleken ook onwerkzaam te zijn. Het gehalte hiervan in de oliefractie hangt echter van de herkomst van de ruwe olie of, omdat ze niet door raffineren van de paraffinestructuren kunnen worden gescheiden.Minerale oliën die aanbevolen worden voor landbouwkundige doeleinden, bezitten normalerwijze een USR boven 95 en een stollingspunt onder 0°C. Dit betekent dat informatie over de aard der oliën op grond van een VGC waarde en over de viscositeit voldoende is om dergelijke oliën te beoordelen op hun geschiktheid de virusoverdracht door bladluizen te kunnen verhinderen.     

The use of species-specific DNA probes for the identification of Mycosphaerella fijiensis and M. musicola, the causal agents of Sigatoka disease of banana

The polymerase chain reaction (PCR)-based technique of random amplification of polymorphic DNA (RAPD) was used to differentiate DNA from species of the genus Mycosphaerella. DNA from two pathogens which cause Sigatoka leafspot diseases of banana, M. fijiensis and M. musicola , and two other Mycosphaerella species which are commonly found on banana, M. musae and M. minima , gave distinct RAPD banding patterns with all PCR primers tested. PCR, using primer RC07, amplified a 1250bp RAPD fragment from all isolates of M. fijiensis obtained from 11 geographical origins. This fragment was absent from the other species of Mycosphaerella. In Southern blots of genomic DNA, this band hybridized exclusively to DNA from M. fijiensis , and the pattern of hybridization suggested that it was binding to repeated DNA. A RAPD band amplified with primer PM06 obtained from M. musicola was also found to be species-specific. Southern analysis suggested that the fragment hybridized to a single-copy sequence in the M. musicola genome. Total genomic DNA from M. musicola was found to be a species-specific hybridization probe. Dot-blots confirmed the specificity of these probes, and could be used to identify isolates of Mycosphaerella which cause Sigatoka disease of banana in south-east Asia.     

Infection process of <Emphasis Type="Italic">Pseudocercospora musae</Emphasis> on banana leaf

Yellow Sigatoka that is caused by Pseudocercospora musae is an important banana disease. The aim of this study was to elucidate the infection process of P. musae in banana leaves by scanning electron microscopy. Leaf samples were inoculated on the abaxial surface with P. musae and then analysed at 12, 24, 36, 48, 72, 96, 120, 144, and 168 h post inoculation (hpi) and at 36 and 50 days post inoculation (dpi). The conidia were found to be germinated between 24 and 36 hpi and penetrated through the stomata between 96 and 120 hpi, or more generally from 144 hpi. P. musae colonized the spongy parenchyma at 36 dpi and the palisade parenchyma at 50 dpi. Sporulation occurred at 50 dpi on the adaxial surface of leaves through the emergence of conidia on conidiophores through the stomata. Considering the importance of yellow Sigatoka in banana production, our results provide a better understanding of the life cycle of the fungus for treatment processes.     

Banana bunchy top disease in Pakistan

The cause of a banana disease in the province of Sindh, Pakistan, was attributed to banana bunchy top virus. Identification was based on symptomatology, size/morphology of the virus particles (20-22 nm) detected in diseased tissue, and serology (DAS-ELISA).     

香蕉枯萎病拮抗菌贝莱斯芽胞杆菌的筛选鉴定及其生物学特性

香蕉枯萎病是目前香蕉产业面临的毁灭性病害,目前尚无特别有效的防治药剂.为发掘香蕉枯萎病的生防菌资源,本研究通过初筛和复筛获得两株对香蕉枯萎病菌具有较强拮抗活性的菌株Blz67和Blz02.依据形态学观察及生理生化测试结果,并结合16S rRNA和gyrA基因序列分析,将两株拮抗菌鉴定为贝莱斯芽胞杆菌Bacillus v...     

韭菜对巴西香蕉枯萎病发生的抑制作用

采取田间试验、盆栽试验及实验室研究相结合的方法,研究了韭菜对香蕉枯萎病的防控效果。田间试验表明,韭菜之后轮作香蕉,第1年香蕉枯萎病平均发病率仅为1.73%（对照为52%）。盆栽试验表明,韭菜处理对香蕉枯萎病发病抑制率为85.9%,病情抑制率为82%;而且韭菜叶片的水提取液对香蕉枯萎病菌（Fusarium oxysporum f.sp.cubense,FOC）孢子增殖抑制率为91.2%,对其致死率为86.97%。本研究表明,韭菜轮作香蕉的种植模式是一种防控香蕉枯萎病的有效途径,而且韭菜及其制剂有望发展成为防控香蕉枯萎病的环境友好型的新型生物试剂。     

助剂在除草剂应用中的作用及发展前景

对助剂在除草剂中的应用历史、国外现状、发展趋势进行了综述。主要内容有助剂在除草剂中的作用,如抗飘移、兼容、沉积、去泡、水质调节等及相应的助剂品种;按来源和化学结构,助剂的类型有表面活性剂类、油类、无机盐类等,这些助剂对除草剂活性提高都有促进作用。文中指出了生物源、环境相容性、低水生生物毒性、易降解、对作物没有毒害的高效新型助剂是助剂开发的方向,并介绍了部分国外新品种;作者还对我国应采取的对策提出了建议。