Control of lettuce drop disease, caused by Sclerotinia sclerotiorum, with metham-sodium soil treatment and foliar application of benomyl

The effects of metham-sodium (MES) soil treatment, a varying number of benomyl foliar sprays (two, three and six) and combined treatments on control of lettuce drop disease were studied at two sites in Israel naturally infested with the pathogen Sclerotinia sclerotiorum. MES killed 85% of the S. sclerotiorum sclerotia in the top 10 cm of soil where initial populations were 0.6 and 1.6 viable sclerotia per kg soil at the two sites. Of the remaining viable sclerotia. only 30% produced apothecia. MES treatment alone reduced numbers of apothecia to 5% of those counted in the unsprayed control treatment. Numbers of ascospores deposited on the crop in the MES-treated plots were 7-20% of those deposited on control plots. Lettuce drop decreased the total yield by 30% in unsprayed control plots; MES application reduced the loss to 4% and also increased the number of marketable plants. Benomyl sprays alone also significantly reduced numbers of apothecia and disease development and consequently increased yield, although not to the extent observed with the MES treatment alone. Combined treatments produced the best disease control, but this improvement was not accompanied by any major increase in yield compared to that with MES treatment alone.     

Forecasting sclerotinia disease on lettuce: toward developing a prediction model for carpogenic germination of sclerotia

ABSTRACT The feasibility of developing a forecasting system for carpogenic germination of Sclerotinia sclerotiorum sclerotia was investigated in the laboratory by determining key relationships among temperature, soil water potential, and carpogenic germination for sclerotia of two S. sclerotiorum isolates. Germination of multiple burials of sclerotia to produce apothecia also was assessed in the field with concurrent recording of environmental data to examine patterns of germination under different fluctuating conditions. Carpogenic germination of sclerotia occurred between 5 and 25 degrees C but only for soil water potentials of >/=-100 kPa for both S. sclerotiorum isolates. Little or no germination occurred at 26 or 29 degrees C. At optimum temperatures of 15 to 20 degrees C, sclerotia buried in soil and placed in illuminated growth cabinets produced stipes after 20 to 27 days and apothecia after 27 to 34 days. Temperature, therefore, had a significant effect on both the rate of germination of sclerotia and the final number germinated. Rate of germination was correlated positively with temperature and final number of sclerotia germinated was related to temperature according to a probit model. Thermal time analysis of field data with constraints for temperature and water potential showed that the mean degree days to 10% germination of sclerotia in 2000 and 2001 was 285 and 279, respecttively, and generally was a good predictor of the observed appearance of apothecia. Neither thermal time nor relationships established in the laboratory could account for a decline in final percentage of germination for sclerotia buried from mid-May compared with earlier burials. Exposure to high temperatures may explain this effect. This, and other factors, require investigation before relationships derived in the laboratory or thermal time can be incorporated into a forecasting system for carpogenic germination.     

蛇床子提取物对茄子根际土壤中黄萎菌数量及植株抗病性的影响

本试验以茄子根际土壤黄萎菌为作用对象,采用浓度为2、4、8、10 mg/mL的蛇床子提取物,通过田间灌施,配合伤根接菌的方法处理茄子幼苗,探讨蛇床子提取物对根际土壤黄萎菌抑制作用及其对植株抗病性的影响.结果表明,不同浓度蛇床子提取物均可抑制茄子黄萎病的发生,其中浓度为8 mg/mL效果最为显著.与清水对照相比,根际土壤中的黄萎菌数量减少了56.67％～69.23％;茄子植株的发病率和病情指数分别减少了53.12％～54.98％、51.26％～56.82％;生长指标的增幅分别为:株高3.68％～9.59％、茎粗3.41％～9.98％、地上部鲜重4.43％～9.47％、根鲜重2.61％～9.57％、叶面积3.56％～9.55％;防御酶活性也有所增加,增幅分别为:过氧化物酶(POD)45.60％～64.23％、多酚氧化酶(PPO)108.62％～255.00％、苯丙氨酸解氨酶(PAL)62.32％～76.04％.上述结果表明,蛇床子提取物会抑制茄子黄萎病的发生,增加植株的抗病性,促进植株生长.     

Effect of inoculum type and timing of application of Coniothyrium minitans on Sclerotinia sclerotiorum: control of sclerotinia disease in glasshouse lettuce

The effects of Coniothyrium minitans inoculum quality and an 8-week interval between inoculum application and crop planting on sclerotinia ( Sclerotinia sclerotiorum ) disease in three successive lettuce crops were investigated in a glasshouse trial. Spore suspensions of three isolates of C. minitans (Conio, IVT1 and Contans) applied at 10⁸ CFU m⁻² and a standard Conio maizemeal–perlite application (06 L m⁻², 10¹¹ CFU m⁻²) were assessed for their ability to control S. sclerotiorum . Only the maizemeal–perlite inoculum (isolate Conio) consistently reduced sclerotinia disease. In the third lettuce crop only, isolates IVT1 and Contans formulated by Prophyta and isolate IVT as an oil–water formulation, all applied as spore suspensions, reduced disease at harvest compared with the untreated control. Recovery, viability and C. minitans infection of sclerotia buried during the 8-week period prior to each of the three lettuce crops, and of sclerotia formed on the crop, were tested. Only the maizemeal–perlite inoculum (isolate Conio) reduced the recovery of sclerotia buried in soil for weeks between inoculum application and crop planting, reducing their viability and increasing infection by C. minitans . Eight weeks was sufficient to enable C. minitans to infect sclerotia of S. sclerotiorum , and may account for disease control. After harvest of the second and third crops, maizemeal–perlite treatment (isolate Conio) reduced the number and viability of sclerotia recovered on the soil surface and increased infection by C. minitans compared with spore-suspension treatments. The effect of inoculum concentration and the influence of soil temperature (varying with time of year) on infection of sclerotia by C. minitans are discussed.     

Effect of foliar salicylic acid and methyl jasmonate applications on protection against pill-bugs in lettuce plants (Lactuca sativa)

The effects were examined of plant-response signaling compounds, salicylic acid (SA) and methyl jasmonate (MeJA), on resistance to pill-bugs (Armadillidium vulgare) attack in lettuce plants. Foliar SA and MeJA applications were made at weekly intervals from the emergence of the plant until one week before harvesting. SA and MeJA induced detectable levels of hydrogen peroxide (H₂O₂) at least during 5 days post-application in these plants throughout their cultivation. On the whole, SA and MeJA in the concentrations and application scheme evaluated in this research did not significantly influence the dry and fresh weight matter of plants, or the chlorophyll and nitrate contents. In addition, both signal elicitors significantly diminished lettuce mortality due to pill-bugs, which was positively correlated with phenolics and flavonoids contents. Our results suggest that SA and MeJA, especially in low concentrations, should be further evaluated in lettuce production and priming resistance.     

植物提取物对油茶炭疽菌的抑菌活性筛选

为开发新型植物源农药,探究油茶炭疽病的生物防治方法,以油茶炭疽病菌(Colletotrichum fructicola)为供试病原菌,采用生长速率法测定了49种植物的70种提取物对油茶炭疽病菌的抑制作用,筛选出活性较好的提取物,并通过浓度梯度试验测定其抑菌毒力。结果表明,在提取物浓度为1 mg/mL时,臭灵丹石油醚萃取物和益母草乙酸乙酯萃取物对油茶炭疽菌抑菌效果最好,抑制率分别为54.48%和50.75%,经毒力测定其有效中浓度(EC₅₀)分别为0.7013和0.6246 mg/mL。本研究为进一步利用臭灵丹、益母草开发植物源抑菌剂提供了一定的理论依据。     

Estimation of secondary metabolites of indigenous medicinal plant extracts and their in vitro and in vivo efficacy against tomato early blight disease in Pakistan

Journal of Plant Diseases and Protection - Fifteen Pakistan’s indigenous medicinal plant extracts were investigated for various secondary metabolites and their potential against tomato early...     

Preparation and characterization of polyclonal antibody against resting spores of Olpidium virulentus, fungal vector of lettuce big-vein disease

Research on Olpidium virulentus, the vector of the serious lettuce big-vein disease, is difficult because its resting spores persist in soil and retain virus for years and the fungus is not culturable. We developed protocols to obtain purified, viable resting spores from infected roots using an enzymatic treatment and two-step density gradient centrifugation and to generate a polyclonal antibody against these spores. The antibody was species-specific in a direct immunostaining assay and in western blots produced two specific bands (ca. 30.5, 29.0 kDa) against resting spores. The detection limit for resting spores in an indirect ELISA was 200 spores/100 μL.     

Antifeedant activity of solvent extracts of neem seed kernel against Spodoptera litura F. and their persistency against sunlight through encapsulation

Abstract

Different solvent extracts of neem seed kernels were evaluated against Spodoptera litura F. on cauliflower, Brassica oleracea var. botrytis leaves. Based on this evaluation, aqueous extract was dissolved in ethanol, and methanol extract in ethanol, and dissolved parts were designated as fraction I and fraction II, respectively. The extracts having more antifeedant activity were encapsulated to achieve stability against the sunlight. Among the solvent extracts tested at 1.0% concentration, methanol extract provided maximum protection (100%) of the leaves followed by ethanol (98.39%) and aqueous (93.01%) extracts. Fraction I and fraction 11 were equally effective at 0.1 % concentration against S. litura larvae and checked more than 70% of leaf damage. However, such extracts were found to be unstable when exposed to sunlight. The pre‐gelatinized starch‐encapsulated products, viz. ρre‐gel I and pre‐gel II were quite stable and afforded more than 68.0% protection to the cauliflower leaves even after 6 days of exposure to sunlight.     

铁线莲属植物上的病虫害及防治

在昆明地区对铁线莲属植物常见病虫害进行了调查 ,发现枯萎病、白粉病、蛞蝓、蜗牛、蠼螋、蚜虫、潜叶蝇和红蜘蛛是该植物的主要病虫害 ,并提出了相应的防治措施     

Long-term foliar persistence and efficacy of spinosad against beet armyworm under greenhouse conditions

BACKGROUND: The immediate lethality caused by spinosad has been widely studied on Spodoptera exigua (Hübner). However, long‐term effects can also provide valuable information on insecticide toxic action. Here, the persistence of spinosad on Capsicum annuum L. foliage and the lethal and sublethal effects of greenhouse‐aged foliar residues of this insecticide on third instars of S. exigua are reported. RESULTS: Foliage was collected at 0, 3, 5, 10, 20, 30, 40 and 50 days after application, and spinosad residues were measured. Residues decreased over time according to first‐order kinetics. The average rate constant and half‐life of disappearance were 4.44 × 10^?3 and 156 days and 5.80 × 10^?3 and 120 days for 60 and 120 mg L^?1 respectively. Larval mortality gradually decreased, corresponding to the residues, but was still appreciable (35 and 65% for 60 and 120 mg L^?1 respectively) when the larvae were fed with foliage collected 50 days after treatment. Subsequently, pupal development was reduced and varied between 20 and 60% and between 21 and 41% for 60 and 120 mg L^?1, respectively, in all ages of leaf residues that were bioassayed. At all time points, the consumption rate by the larvae was reduced between 62 and 84% for both concentrations that were bioassayed. CONCLUSION: It is concluded that, under the present greenhouse conditions, the degradation of spinosad was slower than that reported by other authors in the field, and, because of that, its residues could cause lethal and sublethal effects to S. exigua larvae. Copyright © 2011 Society of Chemical Industry     

Adjustment of soil-surface pH and comparison with conventional fungicide treatments for control of lettuce drop (Sclerotinia minor)

The use of soil-surface applications of finely powdered calcium hydroxide (Ca(OH)₂) to inhibit Sclerotinia minor sclerotial germination and infection at the collar region of lettuce plants is described. In the laboratory, a pH > 8·0 reduced sclerotial germination of the three S. minor isolates tested. In the glasshouse, surface applications of 2–10 t Ca(OH)₂ ha⁻¹ raised the pH of the top 1–2 cm of a duplex sandy loam soil above 8·5 for at least 8 weeks without affecting soil pH within the transplant root zone. There was a linear relationship between the rate of Ca(OH)₂ applied and disease control, with complete disease suppression at 10 t Ca(OH)₂ ha⁻¹. In field trials on two soil types (duplex sandy loam, pH 6·0; and red ferrosol, pH 6·9), a rate of 2·5 t Ca(OH)₂ ha⁻¹, maintained soil-surface pH above 8·5 for 1–3 weeks and provided up to 58% reduction in lettuce drop. Application of polyvinyl alcohol (a soil-conditioning polymer) over the Ca(OH)₂ layer appeared to reduce Ca(OH)₂ loss by wind, but did not improve retention of raised soil-surface pH or disease suppression. Ca(OH)₂ treatment gave similar disease control to the industry standard treatment of a procymidone-based fungicide seedling drench. A combined treatment of Ca(OH)₂ and fungicide drench gave greater control than either individual treatment, and equivalent control to fungicide drench and three procymidone foliar sprays, offering integrated management options. The use of soil-surface-applied Ca(OH)₂ with fungicides, rotation and drip irrigation offers an opportunity for enhanced and sustainable control of lettuce drop.     

莴苣花叶病发生规律和防治的研究

 莴苣花叶病(Lettuce Mosaic Virus)是莴苣上一种重要病害。几年来在病毒特性研究的基础上,我们又在泰安和莱阳两地进行了病害发生和防治的田间试验,现将结果简报如下。     

Antimicrobial activity of essential oils and their components against the three major pathogens of the cultivated button mushroom, Agaricus bisporus

Essential oils of Matricaria chamommilla, Mentha piperita, M. spicata, Lavandula angusti folia, Ocimum basilicum, Thymus vulgaris, Origanum vulgare, Salvia officinalis, Citrus limon and C. aurantium and their components; linalyl acetate, linalool, limonene, α-pinene, β-pinene, 1,8-cineole, camphor, carvacrol, thymol and menthol were assayed for inhibitory activity against the three major pathogens of the button mushroom, Agaricus bisporus, i.e. the fungi Verticillium fungicola and Trichoderma harzianum and the bacterium Pseudomonas tolaasii. The highest and broadest activity was shown by the Origanum vulgare oil. Carvacrol possessed the highest antifungal activity among the components tested.     

Impact of consumer-driven changes to crop production practices on lettuce drop caused by Sclerotinia sclerotiorum and S. minor

Increasing demands for value-added salad products have triggered revolutionary changes in the production practices of vegetable salad crops in recent years. One of the pivotal changes is the adaptation of 2-m-wide beds for increased vegetable biomass per unit area. The move away from the traditional 1-m-wide raised beds in cool-season vegetable production and the associated irrigation practices potentially can have a major influence on diseases affecting cool-season vegetables. To assess the potential impacts of this shift on lettuce drop caused by Sclerotinia minor and S. sclerotiorum, the two bed widths and different irrigation frequencies within each were compared in two separate field experiments over four lettuce crops in 2 years. Treatments included 1- and 2-m bed widths with twice-weekly, weekly and biweekly drip irrigation serving as subplot treatments that were begun immediately following thinning. Incidence of lettuce drop was evaluated weekly thereafter until maturity. For S. sclerotiorum, 36 half-liter soil samples were also collected once each season and assayed for the number of sclerotia, and apothecia were counted weekly in a 10-m(2) area for each plot. Regardless of the species, the effects of bed width and irrigation frequency were both significant. Twice-weekly irrigation and 2-m bed width resulted in higher lettuce drop incidence than other treatments. For S. sclerotiorum, twice-weekly irrigation and 2-m bed width also significantly increased the number of apothecia per unit area and the accumulation of soilborne sclerotia over multiple cropping seasons. Results demonstrated that the 2-m bed width combined with the practiced frequency of irrigations can result in higher lettuce drop caused by S. minor and increased incidence of airborne infection by S. sclerotiorum in the Salinas Valley where, historically, it has not been a serious threat. Increased incidence of S. sclerotiorum infection in commercial lettuce fields in the Salinas Valley between 2001 and 2006 validates these experimental results. These relatively new crop production practices can alter the balance of the two Sclerotinia spp. that has long existed in California.     

紫茎泽兰提取物对棉蚜的毒力及其灭蚜机理研究

紫茎泽兰Eupatorium adenophorum提取物对棉蚜Aphis gossypii有很高的毒杀作用。紫茎泽兰乙醇总提物、其氯仿萃取物以及从氯仿萃取物中分离得到的紫茎泽兰素A对棉蚜无翅成蚜的致死中浓度(LC_(50)浸渍法)分别为167.9、224.7、362.8mg/L。试验表明,紫茎泽兰素A对棉蚜钠-钾-三磷酸腺苷酸酶(Na-K-ATPase)活性有明显的抑制作用。棉蚜经2.00mg/ml紫茎泽兰素A溶液处理12h后,其体内的Na-K-ATPase活性仅为对照组棉蚜Na-K-ATPase活性的21.60％。     

核桃细菌性黑斑病杀菌剂筛选及药效研究

本文以黄单胞杆菌Xanthomonas campestris pv.juglandis(Pierce Dowson)为供试菌株,选用不同浓度的13种杀菌剂进行室内毒力测定。结果表明:有10种药剂对该菌有一定的抑制效果,但只有5种杀菌剂能够产生明显的抑菌圈。其中,四霉素和链霉素的抑菌效果最强,最低抑菌浓度为0.165、3μg/mL,抑菌率为74.76%、69.23%,EC_(50)为12.764、35.318μg/mL。其他依次为乙蒜素、中生菌素和春雷霉素。选用这5种杀菌剂进行盆栽防治试验,四霉素和链霉素的平均防效达74.60%、71.69%,乙蒜素和中生菌素防效分别为65.98%、58.40%,春雷霉素防效最低为39.38%。其结果与室内基本一致。室内试验及盆栽试验结果表明四霉素、链霉素、乙蒜素、中生菌素和春雷霉素可作为防治核桃黑斑病的杀菌剂,其中四霉素为首选杀菌剂。     

Control of lettuce big-vein disease by application of fungicides and crop covers

One of the economically important diseases of lettuce is lettuce big-vein disease (LBVD), which leads to severe yield losses. LBVD is associated with a complex of two viruses, Lettuce big-vein associated virus (LBVaV) and Mirafiori lettuce big-vein virus (MLBVV). These viruses are transmitted by motile zoospores of Olpidium spp. fungi, which persist in the soil for decades through resting spores. In greenhouse and field experiments, this study tested whether changing plant and soil temperatures together with fungicide application would have a significant effect on controlling LBVD in lettuce. Soil fumigation with metam sodium was not effective at controlling the disease, as opposed to treatment with chloropicrin and methyl bromide. Moreover, the fungicides carbendazim and fluazinam were effective in reducing the incidence of Olpidium virulentus. Nevertheless, control of the fungal vector did not seem to be sufficient to control the disease due to the transition ability of the virus under low vector abundance. Crop covers, which affect the favourable environmental conditions for the viruses by lowering soil temperature and raising air temperature, reduced the disease symptoms. Combining fungicides with crop cover had a synergistic effect on reducing disease symptoms, thus providing a sustainable solution for LBVD.     

Activity of cyazofamid against Sclerospora graminicola, a downy mildew disease of pearl millet

The efficacy of cyazofamid was tested against pearl millet downy mildew disease caused by Sclerospora graminicola Schroet. Significant inhibition of sporangial sporulation, zoospore release and motility was observed at 0.3 mg mL(-1), and this concentration also provided good fungicidal activity under in vitro conditions. Under glasshouse conditions, none of the concentrations tested, either 0.01-2 mg mL(-1) as seed treatment or 1-10 mg mL(-1) by foliar application, was found to be phytotoxic. The effect of cyazofamid was tested by seed treatment alone, seed treatment followed by foliar application and foliar application alone. Seed treatment with cyazofamid offered only 19.7% disease control, but seed treatment followed by a single foliar application to diseased plants provided good control over disease, seed treatment with two foliar applications was significantly superior and foliar application alone showed a high level of activity, with 10 mg mL(-1) giving 97.9% disease control. Lack of systemic activity of cyazofamid was evident, root treatment giving disease levels on a par with the untreated control. The fungicide exhibited strong curative activity, but only moderate translaminar activity, with only marginal (34.8%) disease control after treatment of the adaxial leaf surface at 10 mg mL(-1). Loss of cyazofamid activity over time was very low, indicating stable residual and rainfastness activity. These results indicate that cyazofamid has a high potential to be an effective fungicide for the control of downy mildew disease of pearl millet.     

Activity of neem (Azadirachta indica A. Juss) seed kernel extracts against the mustard aphid,Lipaphis erysimi

An aqueous, an ethanolic and a hexane extract obtained from neem(Azadirachta indica A. Juss) seed kernels were tested for insecticidal activity against the mustard aphid,Lipaphis erysimi Kalt. The hexane extract, which exhibited a much higher activity than the two other extracts, had an LC50 of 0.674%. When the hexane extract was partitioned with ethanol, the ethanol-soluble fraction had an LC₅₀ of 0.328%, whereas the ethanol-insoluble part showed no activity even at 1%. Column chromatography of the ethanol-soluble fraction yielded eight compounds: nimbin, epinimbin, desacetylnimbin, salannin, desacetyl-salannin, azadirachtin and two unidentified compounds — a salannin derivative and a nonterpenoid. Of these, only five could be tested. Nimbin and epinimbin exhibited no toxicity at 0.3%, whereas salannin, a salannin derivative and the non-terpenoid gave LC₅₀ values of 0.055, 0.096 and 0.104%, respectively.