Foliar applications of fertilizer salts inhibit powdery mildew on tomato 1 (original) (raw)
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Effect of Mineral Nutrition and Salt Spray on Cucumber Downy Mildew (Pseudoperonospora cubensis)
Plants
It was previously shown that spraying with CaCl2, MgCl2, KCl, and K2SO4 and high N and Mg concentrations in the irrigation water of potted cucumber plants reduced powdery mildew, while medium P and high K concentrations increased powdery mildew. In the present work, we tested the effect of irrigation with N, P, K, Ca, and Mg and spraying with salts on downy mildew (Pseudoperonospora cubensis) of cucumber (CDM). In potted plants, an increase in N concentration in the irrigation water resulted in a major increase in CDM severity, while an increase in K or Ca concentrations resulted in a gradual increase in CDM severity. An increase in P and Mg concentrations in the irrigation water resulted in a major CDM decrease. Spraying with Ca, Mg, and K salts with Cl and SO4 anions resulted in CDM suppression in most cases, and a negative correlation was obtained between the salt and anion molar concentrations and the CDM severity. Using NaCl sprays, both Na and Cl concentrations were negatively...
Journal of the …, 1992
The effect of soluble potassium silicate applied to cucumber (Cucumis sativus L.), muskmelon (C. melo L.), and zucchini squash (Cucurbita pepo L.) on the severity of powdery mildew was examined. Application methods included amending nutrient solutions to a concentration of 1.7 mM Si and foliar sprays containing 1.7, 8.5, 17, and 34 mM Si. Untreated plants and plants sprayed with distilled water were used as controls. The leaves of all plants were inoculated with known concentrations of conidia of Sphaerotheca fuliginea (Schlecht.:Fr.) Poll. (cucumber and mu&melon) or Erysiphe cichoracearum DC.: Merat (zucchini squash) 1 day after the sprays were applied. Inoculated leaves on plants receiving the Si-amended nutrient solution or foliar sprays of ≥ ≥ 17.0 mM Si developed fewer powdery mildew colonies than those on control plants. Results of a separate experiment that included a potassium spray, indicated that the active ingredient of the potassium silicate sprays appears to be Si. Experiments to test the persistence of Si foliar sprays on cucumber demonstrated that a 17 mM Si spray applied 7 days before inoculation with S. fuliginea reduced mildew colony formation.
Effects of Foliar Sprays of Phosphates on Powdery Mildew (Sphaerotheca pannosa) of Roses
Journal of Phytopathology, 1994
Powdery mildew on plants of a local clone of Rosa indica Major was significantly controlled by a single spray of 25 mM aqueous solutions of K2HPO4, KH2PO4 plus KOH, or NaHCO3, all plus Tween 20 (0.5 ml/l) or bupirimate (Nimrod) at 0.5 ml/l, which was applied 4 days before inoculation with conidial suspension of Sphaerotheca pannosa var. rosae.Disease incidence was reduced by 79, 71, 54 and 50%, as compared to controls on plants sprayed with KH2PO4 plus KOH, K2HPO4, NaHCO3 or bupirimate, respectively. Phosphates were suppressive and expressed by disappearance of 99% of the pustules and conidia, as early as 2 days after a single spray on mildewed foliage. This treatment was efficient for at least 9 days after the first application when large infected greenhouse-grown plants were used. Re-application of these salts on the same plants reduced the lesion area by about 90% from that recorded before the application. Phosphate and bicarbonate were more suppressive than the systemic fungicide bupirimate in the early period (up to 2 days). The suppresion effects of bicarbonate and bupirimate, however, were short-term and not persistent, while the phosphate treatments remained significantly suppressive for up to 23 days, when the experiment was terminated. The inhibitory and suppressive effectiveness of phosphate salts is discussed in the light of their possible acceptance as ideal foliar fertilizers which should be considered for use in the field for disease control.Einfluß von Blattbehandlungen mit Phosphaten auf den Echten Mehltau (Sphaerotheca pannosa) an RosenSphaerotheca pannosa var. rosae wurde an Pflanzen einer Rosa indica Major-Klone durch eine einmalige Spritzbehandlung mit Losungen von K2HPO4, KH2PO4 plus KOH, bzw. NaHCO3, die alle Tween 20 (0.5 ml/1) enthielten, oder mit Bupirimat (Nimrod) bei einer Konzentration von 0,5 ml/1 kontrolliert, wenn die Behandlung 4 Tage vor der Inokulation mit Konidien des Pilzes vorgenommen wurde.
European Journal of Plant Pathology - EUR J PLANT PATHOLOGY, 2000
The mechanism by which foliar application of potassium chloride solution reduces symptoms of powdery mildew disease (Erysiphe graminis f.sp. tritici) of wheat was investigated. The hypothesis that potassium chloride reduces mildew by an osmotic effect on spore germination was tested in three glasshouse experiments. Either potassium chloride solution or the osmoticum polyethylene glycol 200 was sprayed on wheat at the three- or four-leaf stage. The plants were inoculated with spores and spore germination and leaf area affected by mildew were assessed. Leaf water potential was determined as a measure of the osmotic effect of the treatments. Spore germination and leaf area affected by mildew were related to leaf water potential using regression analysis in groups on the data averaged over the three experiments. Both spore germination on the leaf and leaf area affected by mildew were reduced as leaf water potential decreased. There was no difference between potassium chloride or polyeth...
Nutrient Status of Cucumber Plants Affects Powdery Mildew (Podosphaera xanthii)
Plants
We examined the effects of applications of N, P, K, Mg, and Ca through an irrigation solution and spraying K, Ca, and Mg salts on cucumber powdery mildew (CPM, Podosphaera xanthii) in potted plants and under commercial-like conditions. Spraying CaCl2 and MgCl2, or KCl and K2SO4, decreased CPM. There were significant negative correlations between the anion-related molar concentrations of the salts and disease severity. Among the sprayed treatments, NaCl provided significantly less CPM control when applied at a low (0.05 M) concentration, as compared with CaCl2 and MgCl2. When sprayed applications of Mg and K salts were analyzed separately from the untreated control, the Cl− salts were found to be more effective than the SO4−2 salts. High N and Mg concentrations in the irrigation water delivered to young, fruit-less cucumber plants reduced CPM, whereas more CPM was observed when the irrigation solution contained a medium amount of P and a high amount of K. In contrast, mature, fruit-b...
Canadian Journal of Plant Pathology, 2008
We devised a cylindrical electrostatic discharge generator to physically eradicate tomato powdery mildew colonizing tomato leaves. The generator consists of a copper needle with a pointed tip, an insulating acrylic cylinder, and an electrostatic voltage generator. The needle is insulated with a vinyl sleeve, except for the pointed tip, and is coaxially fixed in the cylinder and connected to the voltage generator. The needle is negatively charged, and the treated plant is earthed. In initial tests, a corona, characterized by a blue glow, formed at the needle tip as the probe was brought closer to the leaf surface. The distance at which this occurred increased from 16 to 50 mm as the voltage was increased from 5 to 30 kV. If the probe was brought too close to the leaf surface, an arc discharge occurred that caused injury to the leaf. Powdery mildew colonies were destroyed by 2-second exposures at probe distances intermediate to where corona discharge was initiated and where arcing occurred. A probe distance of 25 mm and 30 kV for a 2-second burst was selected to further test the efficacy of the probe for controlling powdery mildew in a greenhouse environment. Tomato plants were grown hydroponically in two open-window greenhouses under a first-truss cropping system. Colonies appeared on tomato leaves 10 to 14 days after transplanting. During the following 2 weeks, these colonies produced abundant progeny conidia that secondarily infected neighboring plants. Corona discharge treatment in one greenhouse, at the stage when colonies first became visible, completely suppressed the spread of the disease compared with a non-treated greenhouse in which disease spread rapidly. The present discharge generator is portable and easy to operate on-site as a part of routine care of hydroponically cultured tomatoes in greenhouses and provides a non-chemical method to control powdery mildew disease. Key words: disease control, tomato powdery mildew, electrostatic field, single-truss cropping. Nonomura et al.: powdery mildew on tomato / disease control / electrostatic discharge 524 Résumé : Nous avons conçu un générateur cylindrique de décharges électrostatiques pour éradiquer physiquement l'oïdium colonisant les feuilles de la tomate. Le générateur est composé d'une aiguille de cuivre pointue à une extrémité, d'un cylindre isolant d'acrylique et d'un générateur de voltage électrostatique. L'aiguille, sauf sa pointe, est isolée à l'aide d'un manchon de vinyle et est fixée coaxialement dans le cylindre et branchée au générateur. L'aiguille est chargée négativement et la plante est reliée à la terre. Lors des tests initiaux, un effluve, caractérisé par une lueur bleue, s'est formé à la pointe de l'aiguille lorsqu'on approcha la sonde de la surface d'une feuille. La distance à laquelle ceci s'est produit a augmenté de 16 à 50 mm quand le voltage a été augmenté de 5 à 30 kV. Si l'on approchait la sonde trop près de la surface de la feuille, il se produisait une décharge en arc qui blessait la feuille. Deux secondes d'exposition suffisaient pour détruire les colonies d'oïdium lorsque la distance à la feuille se situait environ à mi-chemin entre celle permettant la formation de l'effluve et celle à laquelle se produisait la décharge en arc. Une distance de la sonde à la surface de la feuille de 25 mm et une tension de 30 kV appliquée pendant 2 secondes ont été choisies pour vérifier, en serre, encore davantage l'efficacité de la sonde et du traitement. Les tomates étaient produites en culture hydroponique dans deux serres ouvertes, selon la méthode de la grappe unique. Les colonies sont apparues sur les feuilles des tomates de 10 à 14 jours après la transplantation. Dans le cours des deux semaines suivantes, les colonies produisirent d'abondantes conidies qui infectèrent les plantes avoisinantes (infection secondaire). Dans une des serres, le traitement à l'effluve, au stade où les colonies ont commencé à paraître, inhiba complètement
Phytopathologia Mediterranea, 2011
Among foliar diseases of tomato grown in soilless systems, powdery mildew and grey mould (caused by Botrytis cinerea), are the most economically important in northern Italy. The causal agent of powdery mildew in greenhouse tomato crops is frequently Oidium neolycopersici, a pathogen which has spread into several tomato production areas in Europe, North America and Japan (Fletcher et al., 1988; Kiss et al., 2001, 2005; Matsuda et al., 2001), causing signifi cant damage. Despite considerable effort expended in the search for resistance in wild tomato species to powdery mildew (Lindhout et al., 1994; Laterrot et al., 1995; Ciccarese et al., 1998), most of the tomato hybrids available for commercial cultivation are susceptible to O. neolycopersici (Jones et al., 2001). Furthermore, few chemicals are registered for use in soilless crops. For these reasons, other methods of disease control need to be found. Many plant species accumulate silicon (Si) in their tissues and its benefi cial ro...
2010
The effect of biocompatible products on the growth of cucumber powdery mildew (Sphaerotheca fuliginea) was evaluated. Plants were treated with dispersions for solutions of sunflower, olive and neem oils and potassium bicarbonate, potassium silicate and monopotassium phosphate, and compared with azoxystrobim. The most effective treatments for reducing the severity of powdery mildew damage in the cucumber foliage were those that contained the higher doses of potassium silicate, potassium bicarbonate, olive oil, monopotassium phosphate and neem oil showed a disease severity similar to azoxystrobin. Potassium bicarbonate, potassium silicate and oils were phytotoxic. Disease control was worse on climatic conditions with higher temperatures.
HortScience
In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens, including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum, and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by 75 mg·L−1 or greater calcium propionate, but needed 300 mg·L−1 or greater of calcium acetate and 40 mL·L−1 or greater of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by 150 mg·L−1 or greater calcium acetate, 150 mg·L−1 or greater calcium propionate, or 5 mL·L−1 or greater potassium silicate. Phytophthora cactorum was completely inhibited by 300 mg·L−1 or greater calcium propionate, but required 600 mg·L−1 or greater calcium acetate and 10 ...
Phytoparasitica, 1996
The hypothesis that enrichment of the foliage with nitrogen and potassium may enhance host resistance to AIternaria and thus reduce disease severity, was examined for potato and tomato (A. solani) and for cotton (A. macrospora). First, the activity of urea (CO(NH2)2) and the salts NH4NO3, (NH4)2SO4, KNO3, KC1, K2SO4 and KH2PO4 against A. solani and A. macrospora was determined in vitro; each of the compounds tested had a weak inhibitory effect on spore germination ofA. solani (EDso >__ 1000 #g/l) and on mycelial growth of both A. macrospora and A. solani (EDso _> 10,000 #g/l). Next, the effect of foliar application of selected nutrients on A. solani and A. macrospora was evaluated in vivo on detached leaves of tomato and cotton. The diameter of A. solani lesions on leaves sampled from tomato plants treated with KNO3 was significantly smaller (by 56.5%) than that recorded on leaves sampled from untreated plants. A. macrospora severity on leaves sampled from cotton plants treated with urea was significantly lower than that observed on untreated leaves (70.8% reduction) but KNO3 did not affect disease severity significantly. The following step was to examine the effects of foliar application of urea and KNO3 on Ahernaria development in field experiments, two with potato and one with cotton. Foliar application of both nutrients (8-10 sprays in total) did not affect Ahernaria severity as compared with the untreated control in any of the experiments. The fungicides chlorothalonil and tebuconazole, on the other hand, significantly suppressed the disease throughout most of the growing season. A mixture of urea or KNO3 with the fungicides did not further improve the effects of the latter when applied alone. Based on these results, it was concluded that Ibliar application of urea or KNO3 does not affect host response to Ahernaria.