Mildew Of Cucumber Research Articles

Synergy Between Metalaxyl and Mancozeb in Controlling Downy Mildew in Cucumbers

Synergy Between Metalaxyl and Mancozeb in Controlling Downy Mildew in Cucumbers

Synthesis and antimicrobial activity of salicylanilide derivatives. II.

The condensation of 4-halo-o-toluidine with salicylic acid or 5-halosalicylic acid was carried out by the use of phosphorus trichloride in xylene to obtain the salicylanilides 1-13, 4-Halo (or nitro)-o-toluidine, 4-halo-o-nitroaniline or 2, 4-dihaloaniline was condensed with 3, 5-dihalosalicylic acid to provide the salicylanilides 14-30 by the same method. The salicylanilides 2-15, 26 and 27 gave the acetylated compounds 31-46 on treatment with acetic anhydride and pyridine. The salicylanilides 26 and 27 gave the methylated compounds 47 and 48 on treatment with dimethyl sulfate. In the antimicrobial activity tests of the synthesized compounds, 4', 5-dihalo-2'-methylsalicylanilides 1-13 and the acetylated compounds 31-42 showed strong antimicrobial activity against some Eumycetes at the minimum inhibitory concentration (MIC) of 0.8 μg/ml. Compound 3 was shown to have a strong preventive activity against downy mildew of cucumber.

Methods for estimating epidemiological effects of quantitative resistance to plant diseases

A model developed by R.C. Lewontin relating rate of population increase to key parameters of the organism's fecundity curve is described and adapted for use with plant pathogenic fungi. For diseases such as cereal rusts, rice blast, and powdery mildew and downy mildew of cucumber, the sporulation curves for the pathogens have been shown to follow an approximately triangular pattern. In the Lewontin model the key features of the pattern are: A, the time from inoculation to first sporulation (i.e. latent period); T, the time of peak spore production per day; W, the time at which sporulation ceases; and S, the area of the triangle (total reproduction per generation). For exponential increase, the values of A, T, W, and S are related to r 1, the rate of population increase, according to the following equation: [Formula: see text] This equation was used to generate families of curves showing effects on r 1 of changes in the position of the triangle (altering latent period) or area (altering reproduction per generation). Data for barley leaf rust, oat crown rust, wheat leaf rust, wheat stem rust, rice blast, cucumber downy mildew, and cucumber powdery mildew were analyzed according to the model to show the effects of different components of resistance on r 1 for each disease. Predictions from the model for barley leaf rust were compared with published data for components of resistance and rates of disease increase for eight barley cultivars. For cultivars of similar crop canopy type (two cultivars sparse; six cultivars, dense canopies), the predicted r 1 values closely corresponded to observed values. Applications of the model to cultivar mixtures and to integrated control (involving protectant fungicides in combination with quantitative resistance) are also discussed.

Effect of Cationic Surfactants on Powdery Mildew of Cucumber

Several cationic surfactants were tested for their inhibitory activities against powdery mildew of cucumber. Among alkyltrimethylammonium chloride, the octyl derivative was the most effective on the powdery mildew, but caused a little phytotoxicity. Alkyldimethylbenzylammonium chloride used in this experiment showed low effects. Didodecyldimethylammonium bromide was remarkably effective, and caused on phytotoxicity on cucumber plants. Inhibitory effects of didodecyldimethylammonium bromide were observed at various growth stages of the cucumber powdery mildew fungus (Sphaerotheca fuliginea), namely, conidial germination, appressorial formation, haustorial formation, hyphal growth, and sporulation. The compound was effective on the fungus at all stages of the life cycle, especially at haustorial formation, hyphal growth, and sporulation. Also the stained mycelia of this fungus showed a speckled, collapsed membrane system and death of hyphal cell were observed frequently. These results suggest that didodecyldimethylammonium bromide act on the cell membrane.

Control of glasshouse whitefly, Trialeurodes vaporariorum, by an ‘aphid’ strain of the fungus Verticillium lecanii

SUMMARYHeavy infestations of whitefly on glasshouse cucumber plants were controlled below the level of economic crop damage by fortnightly or monthly sprays of Verticillium lecanii spores. The fungus did not spread from glasshouse to glasshouse, or from plant to plant, and often not from diseased whitefly scales bearing fungal spore heads to nearby healthy scales. Some scales survived and the resulting adults laid eggs on new leaves bearing no infected scales, creating another, healthy, generation. This makes regular spraying of new leaves essential. Blastospores were as effective as conidia in controlling scales when sprayed to ‘run off’ at concentrations near 107 spores ml‐1 sprayed on to the undersurfaces of leaves. A fivefold increase in spore concentration at levels near 107 spores ml‐1 usually caused significant improvement in mortality, but increase above this concentration is likely to be unrewarding. Thorough coverage of leaves was found to be vital. Control was impaired by dry conditions and by prolonged air temperatures above 25 °C. The fungicide dimethirimol, used against cucumber mildew, did not impair whitefly control by V. lecanii.

Fungicidal activity of N-benzoylanthranilates and related compounds.

Methyl N-(substituted benzoyl)anthranilates were found to possess inhibitory activity against the powdery mildew of cucumber caused by Sphaerotheca fuliginea. Both the anthranilate and the N-benzoyl moieties were essential for this type of fungicidal activity. Substitution at the 2- and 4-positions of the N-benzoyl group was unfavorable to the activity except for the 4-methoxy group. Substitution at the 3-position varied the fungicidal activity to various extents. The variation in the activity of 3-substituted derivatives was analyzed quantitatively with substituent parameters and regression analysis indicating that the variation in the steric dimension of substituents was most responsible for the activity.

Ｎ‐アシルアミノ酸エステルの植物病原菌生育阻害作用

Nα-cocoyl-L-arginine ethyl ester DL-2-pyrrolidone-5-carboxylic acid salts (abbreviation: CAE) was prepared by neutralization with pyrrolidone carboxylic acid after condensing fatty acids of coconut oil and L-arginine ethyl ester. Tests for protection of plant pathogens were performed because of wide antimicrobial action of CAE. As the results of investigation in laboratory, CAE in the medium had shown remarkable antimicrobial effects to anthracnose of banana, rust of broad bean, sheath blight of rice plant, black spot of pear respectively. Field tests were carried out and growth inhibitory actions to plant pathogens were clearly shown at such concentration as 500 μg/ml to chocolate or red spot of broad bean, 70 μg/ml to black spot of pear and scab of pear, 150 μg/ml to rust of pear, and 500 μg/ml to bacterial leaf spot of cucumber and downy mildew of cucumber. A slightly inhibitory action to powdery mildew of cucumber was also found.

Effect of steckerl with merckdelan K on powdery mildew of cucumber

Effect of steckerl with merckdelan K on powdery mildew of cucumber

Inheritance of resistance to Pseudoperonospora cubensis Rost. In cucumber (Cucumis sativus L.)

Since June 1973 Pseudoperonospora cubensis (Berk & Curt) Rost., which causes downy mildew in cucumber, occurs in the Netherlands. The resistance against this disease appears to be based on one recessive gene in linkage with the dominant gene D for dull green fruit skin colour. It is demonstrated that this recessive gene is also linked with one of the genes for resistance to powdery mildew present in the variety Ashley.

Chemical Control of Powdery Mildews of Cucumber and Okra in the Sudan

SUMMARYThe effect of fungicides on the development of powdery mildews on cucumber and okra was studied. Most of the chemicals tested controlled the disease and significantly increased yields, though a dimethirimol-resistant Oidium sp. appeared on okra. Seed dressing with the systemic fungicides thiophanate and benomyl conferred resistance to the disease for a few days whereas soil application gave protection for more than eleven weeks.

Some studies on the systemic activity of the thiophanate fungicides in plants

AbstractThree closely related fungicides, thiophanate (NF 35), thiophanate methyl (NF 44) and NF 48 have been found to be active against a wide range of diseases including the powdery mildews of apple, cucumber and barley; apple and pear scab and grey mould of soft fruit. This paper deals with the preliminary experiments to compare their relative mobilities and biological persistence in crop plants, using the powdery mildews as indicator infections.NF 44 and NF 48 in particular showed a high degree of systemic activity by root uptake and persistence of action against barley and cucumber mildew but very little systemic activity against apple mildew on potted rootstocks. They have also displayed trans‐laminar and localised movement towards the leaf apex in sprayed cucumber and barley leaves but movement was not so marked in sprayed apple leaves.NF 48 was also active as a seed dressing against loose smut of barley.

Inheritance of Resistance to Powdery Mildew in Cucumber

Inheritance of Resistance to Powdery Mildew in Cucumber

Preliminary studies of an integrated control programme for cucumber pests and an evaluation of methods of introducing Phytoseiulus persimilis Athias‐Henriot for the control of Tetranychus urticae Koch

SUMMARYPreliminary investigations suggest that, when Phytoseiulus persimilis is used to control Tetranychus urticae, the major pest of cucumbers, the control of other pests and powdery mildew can be effected by means of Encarsia formosa for the control of whitefly (Trialeurodes vaporariorum), bed drenches of gamma‐BHC for thrips control and dimethirimol for the control of cucumber mildew (Erysiphe cichoracearum). The parasite Aphelinus flavipes failed to control an infestation of Aphis gossypii in one trial. A comparison of different methods of introducing Phytoseiulus confirmed that the best results were obtained when an even, artificial infestation of Tetranychus urticae was established on the crop before the introduction of the predator.

Structures and pesticidal activities of derivatives of dinitrophenols. XI. Effects of substitution of dinitrophenols with C3 to C13 alpha-branched alkyl groups and of esterification on the eradication of cucumber mildew.

AbstractThe eradication of cucumber mildew caused by Sphaerotheca fuliginea (Schlecht. ex Fr.) Poll. with 2‐(C4 to C13 α‐branched alkyl)‐4,6‐dinitrophenols and 4‐(C4 to C13 α‐branched alkyl)‐2,6‐dinitrophenols was examined. 2‐(C8 to C13 α‐Branched alkyl)‐4,6‐dinitrophenols were highly active, but O‐methylation produced compounds with no activity. 4‐(C7 to C10 and several C11 to C13 α‐branched alkyl)‐2,6‐dinitro‐phenols gave a significant degree of eradication. 2‐(C6 to C13 α‐Branched alkyl)‐4,6‐dinitrophenols were significantly more active than their 4‐alkyl‐2,6‐dinitrophenol analogues. Esterification of C4 to C7 α‐branched alkyl dinitrophenols to methyl‐ or ethyl‐ carbonates or crotonates gave compounds with enhanced activity. Generally, the methyl‐ or ethyl‐ carbonates or 2‐C8‐alkyl‐4,6‐dinitrophenols were as active as the parent phenols, but the higher alkyl carbonates or crotonates had lower activity. Esterification of 2‐(C9 to C13 α‐branched alkyl)‐4,6‐dinitrophenols to ethyl carbonates and crotonates gave compounds with reduced activity.

Powdery mildew resistance in cucumber

Powdery mildew in cucumbers (Cucumis sativus L.) can be caused by two fungi, Erysiphe cichoracearum and Sphaerotheca fuliginea. In The Netherlands we have been mainly concerned with the latter, at least during the last few years.

Pentobarbital Sodium Salt, a Systemic Agent for Control of Powdery Mildew of Cucumber

PHENOBARBITONE (phenobarbital) has been reported to control powdery mildew of marrow1. During 1963 and 1964 we have tested a series of barbituric acid derivatives on powdery mildew of cucumber caused by Sphaerotheca fuliginea (Schlecht. ex. Fr.) Poll.

Effects of fumigants on cotton aphid and powdery mildew of cucumber in the vinyl house

Effects of fumigants on cotton aphid and powdery mildew of cucumber in the vinyl house

Evaluation of the activity of a number of procaine derivatives and analogous compounds against powdery mildew (Sphaerotheca fuliginea) on cucumber*

SUMMARYAbout fifty derivatives and analogues of procaine have been prepared and tested in three different tests for activity against powdery mildew of cucumber. Most of the compounds were active but few equalled procaine.The results obtained seem to afford little evidence for simple structure‐activity relationship based on physico‐chemical or electro‐chemical properties.

Effect of smoking rod for the control of powdery mildew of cucumber

Effect of smoking rod for the control of powdery mildew of cucumber

Effects of Dichlone-rod for the control of powdery mildew of cucumber and leaf mold of tomato in vinyl houses

Effects of Dichlone-rod for the control of powdery mildew of cucumber and leaf mold of tomato in vinyl houses