The effects ofAlternaria solani andVerticillium dahliae on potatoes growing in Israel

Summary The effects of two major fungal diseases of potatoes growing in hot climates, early blight (Alternaria solani) and Verticillium wilt (Verticillium dahliae), were investigated in field trials. Large populations of clones were grown in the Negev, Israel in the Spring and Autumn seasons of three years, 1983, 1984 and 1985. Although symptoms of the diseases were seen in both seasons they were less severe in the Autumn. The effects ofA. solani on yield, when expressed as percent of the control plot yield were also less in the Autumn than the Spring. WithV. dahliae, however, the proportional effect on yield was greater in the Autumn. The decreases in yield associated with the two diseases were examined in terms of losses to the grower. The advantages of breeding for resistance/tolerance to these diseases were clear, emphasising the need for suitable screening techniques.     

Control of foliar diseases by the axillary application of systemic fungicides in Brazilian coconut palms

Endemic fungal foliar diseases, such as leaf blight – LB [Lasiodiplodia theobromae (Pat.) Griffon and Maubl] and leaf verrucosis, or “lixa-pequena” – LP [Camarotela torrendiela Batista (Bezerra) and Vitoria], reduce the productivity of the coconut palm in Brazil. Damage arises from extensive necrosis of the leaflets, resulting in early abscission of basal leaves and fruit. In Brazil, fungicide terrestrial sprayings has not been a commonly employed practice for the control of coconut foliar diseases because it is not cost-effective, once requiring high-volume of fungicide spraying. Coverage gaps and extensive drift of chemicals can occur due to technological limitations of terrestrial spraying of the tallest mature trees and is further complicated by the peculiar architecture of the palms. The aim of this study was to evaluate the efficacy of systemic fungicides applied directly to the leaf axil of the coconut palm (variety Brazilian Green Dwarf of Jiqui) for the control of foliar diseases. During 2007–2010 and 2009–2012, two field plot experiments were conducted at distinct locations (farms) in the North Fluminense region. Two to 4-monthly applications of the fungicides to the leaf axil of cyproconazole (alone), cyproconazole plus azoxystrobin, cyproconazole plus trifloxystrobin, and flutriafol (alone) were efficacious in controlling coconut palm leaf diseases, resulting in a significant reduction of the LB severity and the number of necrotic LP lesions. When compared with the control treatment, significant increases in the total number of leaves per plant were observed for the most efficacious treatments after one year (2–4 leaves more) and after the second year (3–6 leaves more) after initiating the axillary applications of fungicides in both experiments. This trend continued even after the third year, when there was an average of 8 leaves more for the most efficacious treatment (27 leaves per plant) compared to control (19 leaves per plant) at the end of second experiment. The control of foliar diseases based on the results could ensure a significant increase in regional coconut production.     

Economics of foliar fungicides for hard red winter wheat in the USA southern Great Plains

Grain yields of winter wheat (Triticum aestivum L.) in the southern Great Plains are often reduced by the presence of foliar diseases. This study was conducted to determine whether the application of foliar fungicides is an economically optimal management strategy. The effects of fungicide treatment on commercially available hard red winter wheat varieties with differing levels of genetic resistance (i.e., resistant, intermediate, and susceptible) to foliar diseases were investigated at two locations, Apache and Lahoma, OK, USA, for the harvest years 2005–2012. Two fungicides were rotated between the two locations and applied at approximately Feekes growth stage 9–10.5. When averaged across years, plots to which fungicide was applied generated greater average net returns than plots that did not receive fungicide for susceptible varieties at Apache, and for resistant, intermediate, and susceptible varieties at Lahoma. However, foliar fungicide application was not economical in every year at either location suggesting fungicide use should be reassessed each year given that profitability depends on year specific yield potential, prices, and foliar disease conditions. At both locations high disease incidence occurred in all but one site-year when the average March through May relative humidity exceeded 65%. Additional research would be required to determine the relationship between weather, including relative humidity, and disease incidence, and to develop an economic threshold for treatment decision aid.     

In vitro evaluation of Penicillium digitatum Sacc strains sensitivity to various fungicides from Jordan

This investigation is the first report in Jordan, aimed for in vitro evaluation of six fungicides and their combinations, to control the post harvest green mold (Penicillium digitatum) of citrus fruits. Thirty one different concentrations (0.01-3000 microg mL(-1)) of each fungicide, in addition to 6 combined concentrations from each of 7 fungicide mixtures, were tested using Agar well diffusion method against four fungal strains. Regression analysis, one way ANOVA and Post Hoc Multiple comparisons were carried out to test the significance of these treatments. Results of regression analysis indicated significant correlation (p < 0.01) between fungicide concentration (microg mL(-1)) and inhibition zone (mm) of tested strains. All applied fungicides have resulted in complete inhibition of fungal growth in the four tested strains with MIC values ranging from 5 to 2700 microg mL(-1). Canvil and Ranvil of the DMI family were the most effective against tested strains (except strain dg6) where an MIC in the range of 5 to 150 microg mL(-1) was required. Benomyl has worked effectively with the least MIC values against the four tested strains. The obtained Benomyl's MIC values were: 20, 40, 300 and 40 microg ml(-1) against strains dg2, dg4, dg5 and dg6, respectively. One way analysis of variance indicated that the following fungicide mixtures: Benomyl/Canvil; Topsin/Vydan; Blin/Canvil; Topsin/Blin and Topsin/Canvil had significantly (p < 0.001) affected the sizes of inhibition zones, in strains dg2, dg2 and dg5, dg2 and dg4, dg2 and dg4, respectively. Scheffe multiple comparisons analysis showed that there were significant differences (p < 0.001) between the combined concentrations of 50:50 microg mL(-1) or 100:100 microg mL(-1) of Benomyl/Canvil mixture and the rest of tested concentrations where complete inhibition of growth was achieved at a combination of 100:500 microg mL(-1). The mixtures of Benomyl/Canvil and Blin/Canvil were the most effective against strains where, wither complete inhibition or the largest inhibition zones were obtained at the least (50:50 microg mL(-1)) combined concentrations.     

Soil survival and thiabendazole sensitivity ofHelminthosporium solani isolates from Alberta,Canada

Summary Survival of the pathogen causing silver scurf of potato (Helminthosporium solani) in Alberta soils was studied by evaluatingH. solani infection in the progeny ofH. solani-free nuclear seed potato tubers planted in fields where potatoes had never been grown or were grown 1, 2, 3, or 4 years previously. Daughter tubers from all the fields developed silver scurf lesions, andH. solani was isolated from infected tubers. This is the first report of survival ofH. solani in Alberta soils. Soil-borne inoculum appears to have a role in the epidemiology of the disease and in the introduction of the pathogen into silver scurf-free potato seed stock. Of 31 plant species tested, only potato was found to be a host ofH. solani. Most of theH. solani isolates from north central Alberta were more sensitive to thiabendazole than those from southern Alberta, where thiabendazole is much more commonly used.     

Interaction between seed treatments,surfactants and foliar fungicides on controlling dry bean anthracnose (Colletotrichum lindemuthianum)

Anthracnose, caused by fungal pathogen Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi Cav. is one of the main production constraints of the dry bean (Phaseolus vulgaris L.) industry in Ontario. A field study was carried out in 2007 and 2008 to investigate the effect of two seed treatments (DCT (diazinon + captan + thiophanate-methyl) and MFA (metalaxyl-M + fludioxonil + azoxystrobin)) and two foliar fungicides (pyraclostrobin and azoxystrobin) applied with and without a surfactant under low and high disease pressure conditions at Exeter ON. Eighteen treatment combinations were tested in a randomized complete block design with four replicates. The treatment effects were examined by measuring disease development on leaf and pod tissue, pod destruction index, pick (discolored and misshaped seed), yield and return on investment (ROI). The seed treatment MFA performed similarly to DCT, and should be considered a suitable replacement to DCT for dry bean growers. However, utilizing a strobilurin fungicide in both seed and foliar treatments raises concern, as this practice increases the risk of disease resistance. The addition of a surfactant to azoxystrobin increased seed yield and ROI under high disease pressure, but had no effect when added to pyraclostrobin. Pyraclostrobin outperformed azoxystrobin for some disease indices as well as for yield under high disease pressure and for ROI under low and high disease pressure conditions.     

Impacts of foliar fungicides on infection of soybean by Phomopsis spp. in Iowa, USA

Fungicides pyraclostrobin (strobilurin) and tebuconazole (triazole) were applied to soybean [Glycine max (L.) Merr.] at growth stages R3, R5 or R3 + R5, in 2008 and 2009 at two locations in Iowa. Incidence of infection of stems and seeds by Phomopsis spp. was evaluated, along with yield and seed quality. Stem infection by Phomopsis spp. was reduced in both years by pyraclostrobin applied at R3 + R5, and in 2008 by pyraclostrobin at R5, by approximately three-fold compared to the untreated control. In 2009, treatments including applications of tebuconazole at R3 and pyraclostrobin at R5 significantly reduced infection of seed by Phomopsis spp., by approximately two-fold compared to the untreated control. Only the application of pyraclostrobin at R3 + R5 reduced both stem and seed infection by Phomopsis spp. in 2009. None of the treatments had a significant effect on yield, or seed quality, evaluated by warm and cold germination tests. Seed infection by Phomopsis spp. was negatively correlated with seed quality. Fungicides applied at these growth stages can have an impact on infection by Phomopsis spp., but their effectiveness varies with environment and disease intensity.     

Integrated management of major diseases of mungbean by seed treatment and foliar application of insecticide,fungicides and bioagent

Field experiments were conducted during the rainy seasons of 2009 and 2010 for the management of the major diseases of mungbean, namely, wet root rot (Rhizoctonia solani), cercospora leaf spots (Cercospora canescens and Pseudocercospora cruenta) and yellow mosaic (Mungbean Yellow Mosaic Virus) by using different combinations of an insecticide, fungicide, and bio-formulation as seed treatment, with or without foliar sprays. A combination of seed treatment with thiamethoxam (Cruiser™) at 4 g kg⁻¹, carboxin (Vitavax™) at 2 g kg⁻¹ and Pusa 5SD (Trichoderma virens) at 4 g kg⁻¹ followed by simultaneous foliar sprays of thiamethoxam (Actara™) 0.02% and carbendazim (Bavistin™) 0.05% at 21 and 35 days after sowing resulted in the highest seed germination and grain yield in mungbean with the lowest intensities of cercospora leaf spots and mungbean yellow mosaic, and moderate incidence of wet root rot. The lowest whitefly population was also observed in this treatment during all stages of the crop. The treatment combinations having Pusa 5SD as seed treatment provided the lowest wet root rot incidence. Two sprays were superior to single spray for all variables recorded, but in combination with seed treatment, single spray was found to be more cost effective as it obtained the highest return per rupee of input. Use of T. virens based bio-formulation Pusa 5SD with insecticide thiamethoxam has been effectively demonstrated for the first time along with fungicides Bavistin and Vitavax for the management of the major diseases of mungbean.     

Flea beetle (Phyllotreta undulata Kutschera) sensitivity to insecticides used in seed dressings and foliar sprays

Flea beetles of the genus Phyllotreta (Coleoptera: Chrysomelidae), which are severe pests in spring oilseed rape, have become increasingly difficult to control in some areas in Sweden. The current practice for plant protection is to use seed treatments followed by foliar applications of insecticide. Seed treatment with the single, currently registered neonicotinoid insecticide (active ingredient: imidacloprid) was compared to untreated controls and seed treatment with clothianidin using Phyllotreta undulata Kutschera beetles from 10 locations. Beetles from the overwintered generation and the new generation from the same 10 locations were used in bioassays to detect possible reduced sensitivity to the pyrethroid lambda-cyhalothrin. Seed treatment with clothianidin provided better protection for seedlings than imidacloprid. Highly variable results were obtained from the pyrethroid bioassays, but tests performed on beetles collected in August indicated that most sampled beetle populations are still susceptible to lambda-cyhalothrin. It is, however, important that the need for foliar applications is minimized to avoid insecticide resistance selection pressure. This requires seed treatments with adequate efficacy against flea beetles together with cultural control measures that can reduce flea beetle damage.     

Managing crop losses from plant diseases with foliar fungicides, rotation and tillage on a Black Chernozem in Saskatchewan, Canada

The impact of tillage system, rotation sequence and foliar fungicides on diseases and seed yield and quality of wheat, barley, pea, canola and flax was determined in the second cycle of three, 4-year rotations from 1998 to 2001 on a Black Chernozem (Udic Boroll) at Melfort, Saskatchewan, Canada. The objective of the study was to evaluate the impact of reduced-tillage production systems, broadleaf cropping intensity and fungicide use on cereal, oilseed and pulse crops in northeastern Saskatchewan, a sub-humid region of the northern Great Plains. A split-split plot design was used with three tillage systems (conventional, minimum and no-till) as main plots, three rotations of increasing broadleaf crop intensity (1. canola-wheat-barley-barley; 2. canola-barley-pea-wheat; and 3. canola-pea-flax-barley) as sub-plots, and fungicide treatments (treated or untreated) as sub-sub-plots. Fungicides appropriate for the diseases of concern were applied at recommended crop development stages and application rates, followed by assessment of diseases. Tillage system had little impact on diseases of any crop, although seed yield was usually greater under no-till for most crops under dry conditions. Rotation was not a major factor in disease severity of most of the crops, except barley in the rotation where it was grown for two consecutive years. Under dry conditions, barley yield was reduced when it followed flax compared with other crops, most likely due to less available soil moisture after flax. Fungicide application had the greatest impact on disease control and seed yield increase, although results varied among crops and years. In conclusion, the findings indicate that tillage system had little effect on disease severity, rotation contributed to greater disease severity only when a crop was grown intensively, such as on its own stubble, and fungicide application had variable effects on both disease control and seed yield.     

大豆品种对立枯丝核菌的抗性研究!

运用种子腐烂率测试法对208份大豆材料进行测试,研究了根腐病原菌中立枯丝核菌对大豆的致病性,并对抗大豆立枯丝核菌抗源材料进行筛选。结果表明:立枯丝核菌是大豆根腐病病原菌中致病性较强的一种,大部分品种对立枯丝核菌高度感病,高感品种(系)153个,占参试材料的73.55%;高抗品种(系)21个,占参试品种(系)的10.1%,其中有7个来自国外;中抗品种(系)34个,占参试品种(系)的16.35%,其中12个中抗材料为创新改良的稳定品系。     

油菜菌核病菌对嘧菌环胺和不同杀菌剂敏感性的相关分析

为了明确油菜菌核病菌对新型杀菌剂嘧菌环胺的敏感性和该药剂与其它杀菌剂的交互抗性,采用菌丝生长速率法测定江苏省不同地区的53个油菜菌核病菌菌株对嘧菌环胺的敏感性,并测定对嘧菌环胺不同敏感性的10个菌株对菌核净、异菌脲、腐霉利、多菌灵、咪鲜胺和戊唑醇等杀菌剂的敏感性。结果表明,菌株间对嘧菌环胺的敏感性差异显著, EC50（抑制中浓度）值在0.0342～1.087 6μg/mL之间;通过EC50值相关性分析,油菜菌核病菌对嘧菌环胺与上述杀菌剂之间不存在交互抗性。 关     

Pathogenicity ofRhizoctonia solani Kühn to potato leaflets

Summary The extent of invasion of potato leaflets byRhizoctonia solani Kühn was related to the age of the plants sampled. their growing conditions and the cultivar being tested, but not to the sources of the fungal isolates. No correlation was found between behaviour of isolates on leaflets and their characteristics in vitro.

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Zusammenfassung Die Anf?lligkeit von gepflückten Fiederbl?ttern der Kartoffel für Infektionen durchRhizoctonia solani wurde in Versuchen dazu benützt, Unterschiede in der Pathogenit?t zwischen Isolaten festzustellen. die entweder von Sklerotien von Kartoffelknollen aus dem Feldanbau. von L?sionen auf Kartoffelkeimen oder von Getreidehalmen gewonnen wurden. In diesem Artikel ist der Zusammenhang zwischen dem Blattbefall und der Herkunft und den Eigenschaften der Isolate beschrieben. Bl?tter der Testpflanze wurden bis ca. 250 mm unter der Endknospe entfernt. Die beiden vorletzten Fiederbl?ttchen wurden gepflück. w?hrend sechs Stunden in Leitungswasser eingetaucht und dann mit sterilem Wasser abgespült. Die Bl?ttchen wurden dann einzeln mit ihrer Unterseite auf eine Kultur des Versuchsisolats. das auf Wasser-Agar in 90 mm Petrischalen gedieh. gelegt. Die Virulenz jedes Isolates wurde sieben Tage nach der Inkubation bei ca 16°C unter diffusem Tageslicht in Prozent des verf?rbten Gewebes gemessen. Das Ausmass des Befalls der Bl?tter schwankte je nach Sorte (Tabelle 3), Wachstumsbedingunen (Tabelle 1) und Alter der Pflanze bei der Musterentnahme (Tabelle 2), aber nicht nach der Herkunft der Isolate. Zwischen dem Verhalten der Isolate auf den Bl?ttern und ihrer Wachstumsrate in der Kultur. der Art (braun bis peckschwarz). der H?ufigkeit (null bis viel) und der Verteilung (geballt. konzentrisch oder zerstreut) der in vitro oder auf den Sorten. von denen die Isolate gewonnen wurden. erzeugten Sklerotien wurde keine Korrelation gefunden.

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Résumé La sensibilité des folioles de pomme de terre à une inoculation parRhizoctonia solani a été utilisée dans le but de déterminer des différences de pathogénicité entre des souches obtenues à partir de sclérotes prélevées sur tubercules, de lésions sur germes, ou de tiges de blé. Cette publication concerne la relation existant entre le taux d'infestation des folioles, l'origine et les caractéristiques des souches. Les feuilles sont prélevées sur des plantes test à environ 250 mm en dessous du bourgeon terminal. Les deux avant dernières folioles ont été détachées, trempées dans l'eau du robinet durant 6 heures et ensuite rincées dans de l'eau stérile. Les folioles sont placées séparément avec leur épiderme inférieur sur une culture de la souche test poussant en boite de pétri de 90 mm sur milieu eau du robinet-gélose. La virulence de chaque souche est exprimée en pourcentage de tissus décolorés, mesuré après 7 jours d'incubation à 16°C en lumière du jour diffuse. L'extension de la maladie sur les folioles varie en fonction de la variété (tableau 3); des conditions de croissance (tableau 1); de l'age de la plante et de l'échantillon (tableau 2), mais non pas en fonction de l'origine des souches. Aucune corrélation n'a été trouvée que ce soit entre le comportement des souches sur les folioles et leur taux de croissance en culture; la nature (brun à noir de jais), la quantité (zéro à beaucoup) et la distribution (concentré, concentrique ou dispersé) des sclérotes produites in vitro; ou la variété à partir de laquelle les souches ont été obtenues.

     

Sensitivity of Cercospora sojina isolates to quinone outside inhibitor fungicides

Frogeye leaf spot, caused by Cercospora sojina, causes yield reductions to soybean (Glycine max) grown worldwide. Quinone outside inhibitor (QoI) fungicides have been effective in managing frogeye leaf spot, but the risk of selecting C. sojina strains with resistance to this class of fungicides is considered high. A QoI fungicide resistance monitoring program was initiated, in which sensitivities to azoxystrobin, pyraclostrobin, and trifloxystrobin were determined in C. sojina isolates collected prior to QoI fungicide use on soybean (baseline group) and C. sojina isolates collected from soybean fields in 2007, 2008 and 2009. For the baseline group, the mean effective fungicide concentration at which 50% of the conidial germination was inhibited (EC₅₀) was determined to be 0.01287, 0.00028 and 0.00116 μg ml⁻¹ for azoxystrobin, pyraclostrobin and trifloxystrobin, respectively. When mean EC₅₀ values of 2007, 2008 and 2009 C. sojina isolates were compared to baseline C. sojina EC₅₀ values, a small but statistically significant (P ≤ 0.05) shift towards less sensitivity was observed for trifloxystrobin in 2009. Although small (<1.5-fold), this shift in sensitivity indicates a risk of selecting for C. sojina strains with reduced sensitivity to QoI fungicides, and fungicide sensitivities should continue to be monitored in the future.     

Application of fungicides to reduce yield loss in anthracnose-infected lupins

A range of fungicides were evaluated for control of anthracnose (Colletotrichum lupini) in lupin. Glasshouse investigation identified fungicides that reduced disease severity with varying degrees of efficacy. When applied 1 d prior to infection, azoxystrobin, chlorothalonil, mancozeb and copper oxychloride fungicides were highly effective. Systemic fungicides such as tebuconazole, benomyl and carbendazim were less effective. Application timing was important; fungicides such as chlorothalonil and mancozeb were less effective when applied 5 d prior to infection compared with 1 d prior. Application after infection was ineffective for all fungicides. In field experiments application of azoxystrobin, mancozeb or chlorothalonil during flowering and podding reduced incidence of anthracnose infection on pods. Yield responses occurred in moderately susceptible, moderately resistant or resistant cultivars. Seed infection was reduced but not eradicated. Application of foliar fungicides for anthracnose control is potentially a viable management option for lupin production in high anthracnose risk areas of Western Australia.     

花生品种(系)叶部病害综合抗性鉴定

:1 998～ 1 999年在自然发病条件下对 2 0个花生品种 (系 )进行叶部病害综合抗性鉴定。结果表明 ,目前我国广泛种植的花生品种对晚斑病、早斑病、网斑病等主要叶部病害的抗性存在差异 ,缺乏高抗和兼抗性材料。花生对叶部病害的抗性与主茎高、分枝数、结果数、饱果率等农艺性状及其分类类型无显著相关。自然发病条件下花育 1 7和花育 1 6荚果产量较高 ,引进花生品种 UF91 1 0 8产量较低 ,但对晚斑病、网斑病等具高抗水平 ,可提供花生育种作抗源材料     

几种杀菌剂防治甜菜褐斑病效果分析

１９９８ 年在内蒙古林西进行了３ 种杀菌剂防治甜菜褐斑病药效比较试验, 结果表明： 以三苯基醋酸锡效果为最好,褐斑病罹病率较对照低２８ 个百分点, 甜菜根产量、含糖率、产糖量分别比对照提高２２ ．３％ 、１．１ 度、２２ ．６％ 。可在甜菜生产中试用