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1.
2-Methoxyethylmercury chloride (MEMC) applied to cowpea seeds with Rhizobium provided little or no control of seedling rot caused by Rhizoctonia solani; similar treatment, but without Rhizobium, gave >40% control of disease. Treating seeds with quintozene and then with Rhizobium rendered the fungicide completely ineffective against R. solani infections; disease control was >70% when seeds were treated with quintozene only, and >60% when seeds were coated first with Rhizobium and then with quintozene; treatment with quintozene+Rhizobium gave about 25% control. Simultaneous treatment with Rhizobium considerably reduced the efficacy of captafol, chloroneb, carbendazim and thiophanate-methyl. Disease control by carboxin, benomyl and thiabendazole remained unaltered in the presence of Rhizobium, but only thiabendazole gave good control. Seeds treated with MEMC and Rhizobium produced seedlings without root nodules; nodulation was also decreased by captafol and by carboxin but six other fungicides had no effect. The implications of Rhizobium-fungicides interactions are discussed in the context of fungicidal control of root diseases.  相似文献   

2.
The inhibition of the growth of Rhizoctohia solani in vitro by carbendazim was maximal at 20°C and at pH 8. In pot tests using mung bean, maximum protection against ‘damping-off’, caused by R. solani, was obtained when seeds were treated with carbendazim. at 1 g a. i. kg?1 (as a wettable powder) and sown in river sands of pH 7 and 8, kept at a 20°C. Better disease control was obtained in soils kept moist by frequent watering than in soils under water stress. Disease control was best in sandy soil and least in clay loam. The implications of these results, for the antifungal efficacy of carbendazim under diverse soil conditions, are discussed.  相似文献   

3.
Micronutrients, applied to the soil in pot tests, differentially altered the efficacy of nine fungicides used as a seed treatment against cowpea seedling rot caused by Rhizoctonia solani. Boron improved disease control by 2-methoxyethylmercury chloride, quintozene, chloroneb and carboxin, but five other micronutrients reduced the efficacy of the fungicides to varying extents. NPK lowered the efficacy of all the fungicides tested except that of thiabendazole, but carbendazim and benomyl gave maximum disease control in soil treated with a mixture of six micronutrients and NPK. Implications of micronutrient-fungicide interactions are discussed in the context of fungicidal control of R. solani; probable mechanisms of inactivation of fungicides by micronutrients are indicated.  相似文献   

4.
The effects of soil moisture (varying from 15% to 42% (v/v)) and sowing depth (1.5–6.0 cm) on the development of bean plants grown in sterile soil infested by the pathogen Rhizoctonia solani and its antagonist Trichoderma harzianum were studied under greenhouse conditions. The four possible combinations of soil infestation with both fungi were tested. Disease severity, percentage of plants emerged, plant height and dry weight were evaluated 3 weeks after sowing. Emergence rate and growth of plants inoculated only with R. solani were not affected by soil moisture, but in the presence of both fungi, plant emergence, plant height and dry weight significantly decreased when soil moisture diminished. Deep sowing significantly reduced the emergence rate and growth of those plants that were inoculated with R. solani only. However, when the soil was infested with both fungi, the effect of sowing depth was not significant. At a sowing depth of 6.0 cm, the percentage of plants emerged was 50% in the presence of T. harzianum, but only 6.7% when the pathogen was inoculated alone. The antagonist protected bean seedlings from pre-emergence damping-off, reduced disease severity and increased plant growth in the presence of R. solani, especially in moist soil.  相似文献   

5.
Stages of oat–vetch cover crop decomposition were characterized over time in terms of carbon and nitrogen cycling, microbial activity and damping-off pathogen dynamics in organically and conventionally managed soils in a field and a controlled incubation experiment. A measurement of relative growth consisting of radial growth of a fungal colony over non-sterilized soil divided by that over sterilized soil was used as an assay of suppressiveness. No differences in relative growth of Pythium aphanidermatum and Rhizoctonia solani were detected between organic and conventionally managed soils amended with cover crop residue. Significant effects of cover crop decomposition stage on the relative growth of both pathogens were obtained. Relative growth of P. aphanidermatum was highest just after incorporation and decreased 3 weeks after incorporation. Relative growth of R. solani was highest about 20 days after incorporation, and decreased 2 weeks later in the organic system, but continued to increase in the conventional system. In both experiments, the N or C content, C:N ratio or dry weight of retrieved debris were significantly correlated with relative growth of P. aphanidermatum. Relative growth of R. solani was significantly correlated with the C:N ratio of soil or the C or N content of debris. Microbial activity was not consistently associated with relative growth of either pathogen.  相似文献   

6.
Artificial suppression of radish damping-off disease was induced by repeated soil inoculations with Rhizoctonia solani, binucleate Rhizoctonia (BNR) and Sclerotium rolfsii in pot systems. Soils repeatedly inoculated with R. solani and BNR showed suppressive to disease caused by R. solani and S. rolfsii, while soils repeatedly inoculated with S. rolfsii were suppressive to disease caused by S. rolfsii but not by R. solani. Species of Trichoderma were consistently isolated from soils repeatedly inoculated with R. solani, BNR and S. rolfsii. These Trichoderma spp. accumulated selectively in relation to the fungal species that was repeatedly added to the soils. The ratios of the frequencies of T. viride, T. harzianum and T. hamatum were 5:2:2 and 8:5:2 in soils repeatedly inoculated with R. solani and BNR, respectively. In S. rolfsii- inoculated soils, T. koningii was predominantly isolated. T. viride, T. harzianum and T. hamatum isolates obtained from either R. solani or BNR after repeated additions to the soils suppressed radish damping-off disease caused after challenge inoculations with R. solani or S. rolfsii. Among the Trichoderma species, T. viride consistently yielded high levels of suppression. However, isolates of T. koningii obtained from S. rolfsii-infested soils suppressed disease caused by S. rolfsii but failed to suppress disease caused by R. solani. Generally, the species of Trichoderma accumulated in a selective pattern that was closely related to the species of fungal pathogen used to induce the suppressive soil.  相似文献   

7.
BACKGROUND: The widespread acceptance of reduced‐tillage farming in cereal cropping systems in the Pacific Northwest of the United States has resulted in increased use of herbicides for weed control. However, soil residual concentrations of widely used imidazalone herbicides limit the cultivation of barley, which is more sensitive than wheat. In addition, increased severity of the root rot disease caused by Rhizoctonia solani is associated with reduction in tillage. Many crops exhibit altered disease responses after application of registered herbicides. In this study, the injury symptoms in barley caused by sublethal rates of two acetolactate synthase (ALS)‐inhibiting herbicides, imazamox and propoxycarbazone‐sodium, were assessed in factorial combinations with a range of inoculum concentrations of the root rot pathogen Rhizoctonia solani AG‐8. RESULTS: Both herbicides and pathogen had negative impacts on plant growth parameters such as root and shoot dry weight, shoot height and first leaf length, and interactions between pathogen and herbicide were detected. CONCLUSIONS: The results suggested that sublethal rates of herbicides and R. solani could alter severity of injury symptoms, possibly owing to the herbicide predisposing the plant to the pathogen. Copyright © 2012 Society of Chemical Industry  相似文献   

8.
Ten isolates of Trichoderma harzianum were tested for their ability to control lettuce seedling damping-off caused by introduced Rhizoctonia solani. T. harzianum isolates TRC 9 and 28 both reduced damping-off. Dual culture experiments were used to select isolates for the study of antibiotic production and mycoparasitism. T. harzianum isolate TRC 12 produced volatile and non-volatile antibiotics, whilst TRC 33 produced only non-volatile antibiotics. T. harzianum isolates 018-2/Y and TRC 9,15 and 28 mycoparasitized R. solani by coiling around and lysing the host hyphae. It appeared that mycoparasitism was more important than antibiosis in the biological control of damping-off.  相似文献   

9.
Conidia of sevenTrichoderma strains were applied on cucumber or radish seeds as a simple methyl cellulose coating or through an industrial film coating process. The seeds were sown in a peat-based soil artificially infested byR. solani orP. ultimum. Four strains controlled damping-off caused byR. solani when applied as a simple coating or as an industrial film-coating. Also, four strains significantly reduced damping-off caused byP. ultimum in cucumber. A correlation was found between production of volatile antibiotics in vitro and control ofP. ultimum. Survival during storage varied according to the strain. Better survival was observed for two strains, with a decrease in conidial viability of one order of magnitude after storage for three and five months at 15 ° C and 4 ° C, respectively. The results show the feasibility of biocontrol of seedling diseases by some antagonists applied onto seeds through an industrial film-coating process.  相似文献   

10.
Resistance of sugar beet seedlings to Rhizoctonia damping-off caused by Rhizoctonia solani has not been described. A series of preliminary characterisations using a single susceptible host and four different R. solani isolates suggested the disease progression pattern was predictable. Two AG-4 isolates and a less virulent AG-2-2 isolate (W22) showed a comparable pattern of disease progression in the growth chamber where disease index values increased for the first 5–6 days, were relatively constant for the next 7–8 days, and declined thereafter. Seedlings inoculated with a highly virulent AG-2-2 isolate (R-1) under the same conditions showed similar patterns for the first 4 days post-inoculation; however disease index values continued to increase until seedling death at 13–14 days. Similar results were observed in the greenhouse, and a small expanded set of other germplasm lines were screened. One tested germplasm accession, EL51, survived seedling inoculation with R. solani AG-2-2 R-1, and its disease progress pattern was characterised. In a field seedling disease nursery artificially inoculated with R. solani AG-2-2 R-1, seedling persistence was high with EL51, but not with a susceptible hybrid. Identification of EL51 as a source of resistance to Rhizoctonia damping-off may allow investigations into the Beta vulgaris–Rhizoctonia solani pathosystem and add value in sugar beet breeding.  相似文献   

11.
采用菌丝生长速率法测定了乙酸铜、噁霉灵、霜霉威、代森锰锌4种杀菌剂对瓜果腐霉病菌(Pythiumaphanidermatum)的毒力,各药剂的EC50值依次为:30.292 3、5.891 7、34.331 9、65.982 6μg/mL。可见噁霉灵30%水剂对瓜果腐霉病菌表现出较强的毒力。对4种杀菌剂还进行了田间黄瓜猝倒病的防治试验,其防效依次为83.65%、80.14%、80.91%、42.48%。根据室内毒力测定和田间药效试验结果,乙酸铜20%可湿性粉剂、噁霉灵30%水剂、霜霉威盐酸盐722克/升水剂对黄瓜猝倒病均具有较高的防效。  相似文献   

12.
Rhizoctonia solani AG 2-1 was recorded in Central Italy on kohlrabi plants showing root and stem rot. After artificial inoculation the fungus caused damping-off of 7-day-old seedlings and root and stem rot of 4-month-old plants developed after 15 days of incubation. This seems to be the first record ofR. solani AG 2-1 on kohlrabi.  相似文献   

13.
Three isolates of binucleateRhizoctonia (BNR) were tested for biological control of damping-off of cucumber seedlings caused byRhizoctonia solani AG 2-2 and AG 4. BNR isolates L2 (AG Ba) and W1 and W7 (AG A) provided protection of 58 to 71% against virulent isolate C4 of AG 4 and 64 to 75% protection against virulent isolate RH 65 of AG 2-2. Varying protection was provided to the seedlings by the BNR isolates against the virulentR. solani from the two AGs depending on their combination. The BNR isolates did not vary in providing protection to the seedling when tested against virulent C4 when both isolates were inoculated using three different methods,viz. in water agar, combination of water agar and soil and using soil alone. Protection of 58 to 71 % was provided by the isolates when inoculation was done on the hypocotyl using water agar, 62.8 to 75% using the combination of water agar and soil, and 75 to 85% when inoculation of both isolates was done in soil. Pre-incubation of BNR W7 or delayed inoculation of C4 (from 0.5 day to longer duration) using the different methods provided an increased protection to the seedlings to give complete inhibition of damping-off disease. Simultaneous inoculation of both BNR W7 and C4 using the three methods failed to provide protection to the seedlings. Among the BNR isolates, BNR W7 showed plant growth promotion in terms of significant increase in plant height (P=0.01) and fresh weight (P=0.05).  相似文献   

14.
Four herbicides commonly used in Israel for controlling weeds in peanuts were evaluated under field and screenhouse conditions. Terbutryn (Terbutrex 50, w.p.), ethalfluralin (Sonalan 333, e.c.), dinitramine (Cobex 240, e.c.) and alachlor (Alapaz 480, e.c.), used at recommended levels, had no adverse effect on nodulation rate, nitrogenase activity, total nitrogen of peanut tops or pod yield, compared with control (inoculated but herbicide non-treated) plants. Studies were conducted to determine the relative toxicity in vitro of the herbicides on each of four Rhizobium strains used for commercial peat inoculant production. The results showed that at up to 94 μg g?1 the herbicides has no inhibitory effect on the growth of rhizobia. The sensitivity of Rhizobium strains to different rates of the chemicals decreased in the order: dinitramine>alachlor>ethalfluralin>terbutryn. It was found that various strains differ in their sensitivity to the herbicides tested.  相似文献   

15.
本文报道了在辽阳地区土壤条件下,用化学药剂防治松苗立枯病(Rhizoctonia solaniKühn,Fusarium sp.)效果不明显、而施入森林腐殖土防治该病取得了极显著效果。方法是将森林腐殖土按每平方米苗床10千克用量与苗床10公分表上掺拌均匀。防病原因是:1.腐殖土中含有大量菌根菌,该菌与苗根形成菌根,有利于水分及无机盐类的吸收、利用。菌根菌又有抑制立枯病菌的作用;2.增加了土壤中有机质及N、P、K的含量,苗木生长健壮,提高了抗病能力。  相似文献   

16.
Biotic and abiotic factors from soils have been implicated in the disease suppression of Rhizoctonia solani. This study included a Eucalyptus twig baiting assay, disease index and qPCR quantification of R. solani, and physicochemical analysis of 10 tobacco soils from five different locations (V: Vaqueros, C: Cerrillos, R: Rosario de Lerma, SA: San Agustín, CH: Chicoana) in the northwest of Argentina. Levels of Rhizoctonia soil inoculum quantified by baiting assay and qPCR were positively correlated. However, there was no correlation with root rot disease index in tobacco fields. Soils from V1, SA2 and CH2 fields, which reduced root rot disease on tobacco plants, were suppressive to R. solani infection. High clay, pH, organic matter content and physical stability in tobacco soils were the main physicochemical properties that limited Rhizoctonia development. Interestingly, growth of R. solani subgroups AG4-HGI and AG4-HGIII was highly suppressed in V1 and CH2 fields, and in SA2 fields, respectively. Undisturbed soil from a local forested mountain also resulted in reduction of growth of AG4-HGIII and AG4-HGI, while AG2-1 was less affected, suggesting that high soil organic matter contributed to suppression of R. solani. Soils highly suppressive of R. solani had significantly different populations of culturable bacteria, Pseudomonas and fungi, but populations of actinobacteria and Trichoderma spp. did not differ. These different populations may be involved in the inhibition of fungal growth. The results demonstrated that physicochemical and biological properties of soil suppressive to R. solani could act as an alternative for controlling Rhizoctonia diseases on tobacco.  相似文献   

17.
Vicia sativa (L.) was subjected to pre-emergence treatments of alachlor, fluchloralin, nitrofen and prometryne. A study of stomatal index was made by collecting leaves from the fourth and fifth nodes of plants. Nitrofen and prometryne, although increasing the number of epidermal cells and stomata per unit area, did not lead to changes in the stomal index compared to control values. Alachlor and fluchloralin reduced the stomatal index greatly because the density of epidermal cells was increased more than the density of stomata. The results are discussed. Effet de quelques herbicides sur l'épiderme de Vicia sativa (L.) Vicia sativa (L.) a été soumise à des traitements en prélevée avec l'alachlor, la fluchloraline, l'azote et la prométryne. Une étude de l'index stomatal a été faite en récoltant des feuilles sur les quatriéme et cinquiéme n?uds des plantes. L'azote et la prométryne, bien que provoquant un accroissement du nombre des cellules épidermiques et des stomates par unité de surface, n'ont pas amené de changement de l'index stomatal comparativement aux valeurs du témoin. L'alachlor et la fluchloraline ont fortement réduit l'index stomatal parce que la densité des cellules épidermiques s'est plus accrue que la densité des stomates. Les résultats sont discutés. Effet de quelques herbicides sur l'épiderme de Vicia sativa (L.) Vicia saliva (L.) a été soumise à des traitements en prélevée avec l'alachlor, la fluchloraline, l'azote et la prométryne. Une étude de l'index stomatal a été faite en récoltant des feuilles sur les quatrième et cinquième nceuds des plantes. L'azote et la prométryne, bien que provoquant un accroissement du nombre des cellules épidermiques et des stomates par unité de surface, n'ont pas amené de changement de l'index stomatal comparativement aux yaleurs du témoin. L'alachlor et la fluchloraline ont fortement réduit l'index stomatal parce que la densité des cellules épidermiques s'est plus accrue que la densité des stomates. Les résultats sont discutés. Die Wirkung einiger Herbizide auf die Epidermis von Vicia sativa (L.) Alachlor, Fluchloralin, Stickstoff und Prometryn wurden vor dem Auflaufen von Vicia sativa (L.) appliziert. Um den Stomataindex festzustellen, wurden Blätter vom 4 und 5 Nodium entnommen. Die Stickstoff- und Prometrynbehandlungen bewirkten zwar eine Zunahme der Epidermiszellen und der Stomata je Flächeneinheit, hatten aber im Vergleich zur Kontrolle keine Veränderungen des Slomataindex zur Folge. Alachlor und Fluchloralin verkleinerten den Stomataindex sehr stark, da die Dichte der Epidermiszellen stärker zunahm als die Dichte der Stomata. Die Ergebnisse werden diskutiert.  相似文献   

18.
The objective was to identify and characterize the causal agent of foliar necrosis and leaf scorch of Eucalyptus spp. in Brazil. Nineteen putative isolates of Rhizoctonia obtained from Eucalyptus plants during clonal propagation were compared with isolates from other hosts and with tester strains of anastomosis groups of Rhizoctonia solani. Features compared were morphological characteristics of anamorphs and teleomorphs, numbers of nuclei per cell in the vegetative hyphae, anastomosis of hyphae, and ability to produce necrotic lesions on cuttings and damping-off of E. grandis×E. urophylla hybrid seedlings. Rhizoctonia solani AG1 (AG1-IB like) was the most frequent causal agent isolated from Eucalyptus plants and cuttings with symptoms of leaf scorch and foliar necrosis respectively. These isolates were highly virulent on Eucalyptus cuttings and presented naturally epiphytic growth on Eucalyptus shoots. Binucleate isolates and isolates of R. solani AG4 were also virulent on cuttings and were most virulent on Eucalyptus seedlings causing pre- and post-emergence damping-off. Virulence on Eucalyptus cuttings and seedlings was not restricted to a single species or anastomosis group of Rhizoctonia.  相似文献   

19.
种子处理对西瓜苗期3种病害的防治效果   总被引：1，自引：0，他引：1  
为了筛选防治西瓜苗期立枯病、猝倒病和枯萎病的有效种子处理剂,在人工控制的条件下,选择了6.25%精甲·咯菌腈悬浮种衣剂、2.5%咯菌腈悬浮种衣剂、3.5%精甲·咯菌腈悬浮种衣剂、72%霜霉威盐酸盐水剂和50%多菌灵可湿性粉剂5种杀菌剂对西瓜种子进行处理。分析了处理种子的活力和幼苗的生长特性;以及在人工接种3种病原菌的胁迫下不同处理种子在基质中的出苗率和发病情况。结果表明:5种杀菌剂对种子的活力和幼苗的生长特性没有明显的影响,但3.5%精甲·咯菌腈悬浮种衣剂包衣降低了每株幼苗的鲜重,50%多菌灵可湿性粉剂浸种则提高了幼苗的整齐度。接种西瓜立枯病菌和猝倒病菌的种子出苗率降低,接种西瓜枯萎病菌的种子出苗率没有明显变化;6.25%精甲·咯菌腈悬浮种衣剂和2.5%咯菌腈悬浮种衣剂包衣种子对西瓜立枯病的防效最佳,72%霜霉威盐酸盐水剂浸种对西瓜猝倒病有一定的防效,对西瓜枯萎病的防治没有特别有效的药剂。  相似文献   

20.
Abstract

In field experiments conducted at the Nyankpala Agricultural Station, Ghana, during 1976–77, soil moisture conditions appeared to be the deciding factor in determining the frequency of handweeding needed to obtain maximum seed cotton yields. In 1976, when planting was early and the late, heavy rains in October prolonged weed growth, two handweedings at 4 and 8 weeks after seeding (w.a.s.) gave comparable yields to continuous weeding and significantly better yields than an alachlor + fluometuron herbicide mixture. Supplementary weeding did not enhance the mixture's performance.

In 1977, planting was relatively late and in the peak of the rainy season and so late weed growth was reduced. A single handweeding at 4 w.a.s. gave as good a yield as repeated handweeding treatments under these conditions. The alachlor + fluometuron mixture also gave adequate weed control and again supplementary weeding did not improve it significantly.

In herbicide evaluation experiments, the safety and performance of pendimethalin and dinitramine herbicides were much influenced by the rainfall pattern immediately following application. With a relatively drier period following application in 1976, the higher rate of these herbicides depressed yields. This rate produced optimum yields in 1977, however, when a very wet period followed application.

Prodiamine and the alachlor + fluometuron mixture were the herbicides least affected by soil moisture and they consistently produced good yields.  相似文献   

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