Foliar-fertilizer therapy — a concept in integrated pest management

Biological control mechanisms of D-pinitol against powdery mildew in cucumber

The powdery mildew caused by Oidium spp. is an important disease for several crops of the Cucurbitaceae family. Although the teleomorphs, Podosphaera xanthii and Golovinomyces cichoracearum, currently have already been described as the causal agents of powdery mildew in Brazil, only P. xanthii is considered the main causal agent of powdery mildew field epidemics. The objective of this work was to identify and determine the prevalence of the species causing powdery mildew in cucumber (Cucumis sativus) and melon (Cucumis melo var. reticulatus) grown in greenhouses in the State of Paraná in Brazil. The morphological traits of the conidial stages, such as the presence of fibrosin bodies and a germinative tube, were used to identify the species. Leaves exhibiting high severity of powdery mildew were collected from plants of 13 plastic greenhouses during different seasons in 2003/2004 and in different regions of Paraná State. In all environments, a significant prevalence of P. xanthii (80-100%) was observed affecting parthenocarpic or ordinary cucumber and melon. Golovinomyces cichoracearum was observed in six greenhouses, with up to 20% of conidia of this species on the samples.

Erysiphe cichoracearum and Sphaerotheca fuliginea are the primary pathogens responsible for powdery mildew in pumpkin (Cucurbita moschata L.), a major fungal disease leading to substantial yield losses. The severity and disease development in pumpkin have led to severe yield losses; hence, a detailed study to assess the efficacy of systemic fungicides and combined fungicides under In vitro conditions is very important. The present study was undertaken during the Zaid and Kharif seasons of 2024–25 to evaluate the efficacy of selected fungicides under field conditions and their effect on mycelium germination inhibition. A total of six fungicides were tested against powdery mildew, and all treatments significantly reduced disease intensity compared to the untreated control. Among them, three sprays of Triadimefon + Bitertanol (Trooper 75 WP) at 0.2% emerged as the most effective treatment, recording the lowest mean Per cent Disease Intensity (PDI) of 19.01%. This was followed by Propiconazole 25% EC + Hexaconazole (Cantof 5% EC) at 0.1% and Myclobutanil (Systhane 10 WP) at 0.2%, with mean PDIs of 22.22% and 27.89%, respectively. Based on the overall disease control performance and disease suppression, Triadimefon + Bitertanol and Propiconazole + Hexaconazole can be recommended for the effective management of powdery mildew in cucumber under field conditions. These treatments can contribute to improved plant health and potentially higher yields when integrated with proper cultural practices. These findings indicate that the use of systemic and combination fungicides can provide effective management of powdery mildew in cucumber, thereby contributing to healthier crops and improved yields under field conditions.

Heat shock treatment (HST) and UV-B irradiation can reduce pathogen infection in crops. However, information on the mechanism of UV-B action is limited. Here, we investigated the mechanism of UV-B-induced resistance against powdery mildew in cucumber and compared it to that of heat-shock-induced resistance. We measured the percentage of leaf area showing disease symptoms and examined the expression levels of defense- and heat-shock-related genes across treatment groups. UV-B irradiation (intensity, 5 µW/cm2) for 4 h/d followed by pathogen inoculation reduced the appearance of powdery mildew by 21.17% compared with the control group. Unlike HST—which induces systemic resistance—UV-B irradiation induced local resistance in cucumber, as indicated by local changes in gene expression (Chi2 and ETR2). UV-B-treated plants inoculated with powdery mildew showed higher expression levels of Chi2, ETR2, and LOX6 than plants that were either treated with UV-B or inoculated. UV-B had no major effects on systemic acquired resistance or heat shock transcription factors, which are known to be affected by HST. Combined HST and UV-B had a strong synergistic effect in reducing powdery mildew in cucumber. Our results indicate that UV-B treatment likely operates through a different mechanism than HST in triggering cucumber resistance against powdery mildew infection.

Powdery and downy mildews caused by Sphaerotheca fusca and Pseudoperonospora cubensis are the most common and serious diseases of cucumber worldwide. In spite of the introduction of highly effective systemic fungicides, control of these diseases remains elusive. Hence, this study aimed to develop an alternative method to chemicals in controlling the diseases by using different types of cooking oil. Egg yolk, which contains a natural emulsifier, lecithin, was selected as a surfactant to emulsify the oils. Among the different cooking oils used, soybean, canola (rape seed), safflower, sunflower, olive, and corn oils showed over 95% control values against powdery mildew of cucumber in a greenhouse test. In particular, 0.3% canola oil emulsified with 0.08% yolk (1 yolk and 60 ml canola in 20 l spray) was found to be the most effective. The treatment resulted in 98.9% and 96.3% control efficacies on powdery and downy mildews, respectively, of cucumber in the field. Canola oil exhibited direct and systemic effect, wherein powdery mildew of cucumber was suppressed only on treated leaves but not on non-treated leaves in a plant, while mycelia and conidia of the pathogen were severely distorted or destroyed by the treatment. The prospect of using the canola oil and yolk mixture as a natural fungicide is highly promising because of its effectiveness, availability, low cost, simple preparation, and safety to humans and the environment. The use of the canola oil and yolk mixture is expected to be an effective fungicide for use in organic farming and home gardening.

Ozonized sunflower oil (oleozon) is an effective agent for controlling powdery mildew in cucumber. In this study, the mechanisms of oleozon in the control of powdery mildew were determined. The development of Podosphaera xanthii on cucumber leaves treated with oleozon (2%) and water was investigated at different times after inoculation. The germinating conidia, hyphae and conidiophores of the pathogen were severely damaged by oleozon. No visible phytotoxic effect was observed on cucumber after the application of oleozon. This compound had highly preventive effects as well as curative effects against powdery mildew based on in vivo potted seedling assays. The control effects of oleozon were further confirmed in a greenhouse trial. These results may provide a basis for further development of a natural fungicide against cucumber powdery mildew.

Relative biochemical and physiological docking of cucumber varieties for supporting innate immunity against Podosphaera xanthii

Podosphaera xanthii causes powdery mildew of cucumber, and is associated with significant yield and quality losses. Development of resistant or tolerant varieties is the most effective and eco-friendly strategy for powdery mildew management. An important host resistance mechanism is based on the recognition of conserved resistance genes, resulting in durable resistance. To determine powdery mildew resistance mechanisms in cucumber, total RNAs were isolated from the powdery mildew resistant cultivar Meltem, the tolerant line VT18, and the susceptible local variety Camlica. Expression levels of nine genes in these plants were analysed by Reverse Transcription Polymerase Chain Reaction (RT-PCR). The host reactions were assessed using microscope observations of stained specimens. Serine/threonine (STN7), transcription factor (WRKY22), serine/threonine-protein kinase (D6PKL1), and serine/threonine receptor kinase (NFP) genes were induced, as positive regulators in defence mechanisms against powdery mildew. Polygalacturonase Inhibitor (PGIP) did not express after P. xanthii inoculation of Camlica, resulting in susceptibility. After inoculation, callose synthase (CALLOSE) and cinnamyl alcohol dehydrogenase (CAD) gene expression levels were increased in resistant Meltem, but Hypersensitive Reaction (HR) and ROS formation were only linked in the tolerant VT18. Powdery mildew development was less in Meltem than in VT18, indicating that cell wall thickening and HR play separate roles in resistance to this disease.

Effectiveness of whey against zucchini squash and cucumber powdery mildew

Powdery mildew on rose ( Sphaerotheca pannosa ) and cucumber ( Sphaerotheca fuliginea ) are two serious diseases in glasshouses. Intensive control by fungicides is needed. The research presented here deals with biocontrol of powdery mildew on cucumber and rose by means of mycoparasites.The mycoparasites Ampelomyces quisqualis , Sporothrix rugulosa and Tilletiopsis minor and Verticillium lecanii were tested on rose powdery mildew. V. lecanii produced the best results. For biocontrol at glasshouse scale an efficient production method of phialoconidia of V. lecanii was developed. In exploratory glasshouse experiments V. lecanii was superior to S. rugulosa in controlling cucumber mildew. Especially on a partially resistant cucumber cultivar biocontrol by V. lecanii showed prospect.To identify characteristics for the selection of V. lecanii isolates with high potential for biocontrol under glasshouse conditions, effect of water limitation on 14 isolates was explored. Conidial germination, growth and sporulation were all clearly affected by humidity, but showed no correlation with mycoparasitic potential. The effect of timing the biocontrol treatment by V. lecanii was studied on rooted mildewed cucumber leaves. At high humidity early preventative and early curative treatments gave considerable reduction in mildewed leaf area. In semi-commercial glasshouse experiments our V. lecanii isolate, A. quisqualis and Sporothrix flocculosa were tested against cucumber powdery mildew.A. quisqualis did not control the disease. V. lecanii had only minor effects. S. flocculosa gave the best control. The failure of biocontrol by V. lecanii was attributed to low humidity in the glasshouse. Formulation of V. lecanii with arachid oil significantly reduced its humidity dependence. Possibilities for integrated control are combinations of partially resistant cultivars, formulation of V. lecanii and combination of V. lecanii with fungicides.

Characterization, biochemical defense mechanisms, and antifungal activities of chitosan nanoparticle-encapsulated spinach seed essential oil

SummaryThe efficacy of candidate activators of systemic acquired resistance (SAR), Bion® (Syngenta, Basel, Switzerland), Rezist® (Stoller Enterprises, Houston, Texas, USA), and Milsana® (P. J. Margo Pvt. Ltd., Bangalore, India), was evaluated for the control of powdery mildew (Podosphaera xanthii) on cucumber and zucchini. Each candidate activator significantly reduced the incidence of disease on both crops in a glasshouse, where spore inoculum was applied to treated leaves. Both Bion® and Rezist® induced increased chitinase activity in plants, confirming their action as activators of SAR. However, Milsana® did not have this effect, suggesting that its mode of action was as a direct inhibitor of infection by spores. In the field, two or three applications of Bion®, at 14-day intervals, gave consistently better results in protecting cucumber plants from powdery mildew. Several applications of Milsana® alone were less effective than a single application of Bion® alone. However, several applications of Bion® adversely affected plant growth, resulting in lower yields. The application of Milsana® before or after Bion® provided effective control of powdery mildew and minimised the adverse effects of Bion® on yield. Application of all three candidate activators alone, on field-grown zucchini did not control powdery mildew, although a systemic increase in chitinase activity occurred in response to Bion® or Rezist®. A greater understanding of the mode of action of Milsana®, and of the interaction between disease load and the timing of activator application(s) may improve the control of powdery mildew.

Powdery mildew, caused by Podosphaera xanthii, is a significant disease impacting cucumber (Cucumis sativus L.) crops, leading to major yield losses. The study evaluates the efficacy of botanicals and biostimulants in managing powdery mildew under in vitro conditions. Treatments were tested at three concentrations (5, 7.5 and 10%) against P. xanthii. Results revealed that the efficacy of treatments increased with concentration, with Ascophyllum nodosum (seaweed extract), Mimosa pudica (touch-me-not) and Osmium sanctum (tulasi) demonstrating the highest inhibition rates at 10%. These findings suggest the potential of eco-friendly alternatives for managing powdery mildew in cucumber.

A single spray of 0.1 M solution of phosphate (K2HPO4, KH2PO4 (pH 4.5 or 9.3) NH4H2PO4), or potassium (KCl, KNO3, K2SO4) salts on the upper surface of the first true leaf of cucumber, before inoculation with Sphaerotheca fuliginea, induced up to 94% systemic protection to powdery mildew on leaves 2-5. Spraying of a 1:1 mixture of both phosphate and potassium fertilizer salts did not improve the protection as compared with that obtained by each of the salts alone. The protection on the upper leaves remained efficient up to 25 days after inoculation regardless of the high concentration of challenge inoculum of S. fuliginea. Postinoculum application of phosphate on the first leaf induced systemic protection against powdery mildew on upper leaves, even when sprayed 4 days after inoculation. The efficiency of induction of systemic protection and curative properties of phosphate and potassium fertilizers can be considered for disease control in the field.

Over 800 open-pollinated (OP) varieties of sweet corn were grown and named in the century prior to the development of hybrids, but only a few of the historically important OP cultivars exist today. Alleles that could improve disease resistance of modern sweet corn may be present in the OP cultivars still in existence. The objectives of this research were to compare 36 OP sweet corn cultivars to modern commercial hybrids for reactions to Stewart's wilt, common rust, northern leaf blight (NLB), and southern leaf blight (SLB), and to classify the OP cultivars based on phenotypic reactions to these four diseases. Plants were inoculated in 1994, 1995, and 1996 with Erwinia stewartii, Puccinia sorghi, Exserohilum turcicum, or Bipolaris maydis. Symptoms were rated on a whole-plot basis, and ratings were analyzed by analysis of variance (ANOVA). Means were separated by Bayesian least significant difference values. Some of the OP cultivars had phenotypes that were intermediate to moderately resistant to Stewart's wilt, common rust, NLB, or SLB, but none of the cultivars were more resistant than the best commercial hybrids. Distributions of ratings for rust, NLB, and SLB were less disperse for the OP cultivars than for commercial hybrids. Hence, the resistance of modern sweet corn germ plasm to Stewart's wilt, rust, and NLB appears to be greater than that of the OP cultivars. OP cultivars and four standard hybrids were placed into groups based on a hierarchical cluster analysis of disease reactions. The seven groups formed from the cluster analysis of disease ratings were considerably different than those formed from isozyme variation and morphological characteristics. The partial resistance of some cultivars, e.g., Golden Sunshine, Country Gentleman, Stowell's Evergreen, and Red, may be relatively diverse since these cultivars were placed in different groups based on isozyme and morphological variation. OP cultivars with moderate levels of resistance may be sources of resistance alleles not present in commercial hybrids.