Application Of Systemic Fungicides Research Articles

Evaluation of phytochemical responses and paclitaxel content of yew (Taxus baccata) seedlings subjected to the systemic fungicides

AbstractEndophytic fungi pass all or at least a part of their life cycle inside or between host cells in living plant tissues. These fungi are not capable of causing disease in the host plants, however, they are deemed to be associated with the production of some secondary metabolites in plants. Therefore, this study was laid out to shed light on how fungicides are involved in the formation of key metabolites of yew (Taxus baccata L.), especially taxol. Through the symbiotic fungal endophyte activities and population changes an experiment was conducted as a completely randomized block design using two foliar application treatments of Rovral‐TS and Fosetyl aluminium fungicides. Plants sprayed with distilled water were used as a control. The findings revealed that the diversity of endophytic fungi declined with the application of systemic fungicides, leading to a decrease in the production of certain secondary metabolites. Specifically, the levels of paclitaxel decreased by 35%, while the photosynthetic pigments chlorophyll‐a, chlorophyll‐b and total chlorophyll decreased by 26%, 20.6% and 19.6%, respectively. Additionally, the levels of carotenoids, total phenol and total flavonoids decreased by 18%, 15% and 21.8%, respectively. The highest amount of these compounds was observed in the control treatment. An increase in antioxidant activity, soluble sugars and proline content was observed soon after fungicides application. The variation in the content of soluble sugars, proline and antioxidant activity was fungicide‐dependent. Compared to Fosetyl aluminium fungicide, the numerical value of the above parameters in plants treated with Rovral‐TS was 14.4%, 11.7% and 25.4% higher, respectively. The fungicide‐mediated induction of Taxol production—key secondary metabolites in yew—was to a great extent associated with the change in endophytic fungi. This further establishes the role of fungal endophytes in the stimulation of secondary metabolite formation in yew plants.

Prevalence and harmfulness of winter wheat brown leaf rust (Puccinia recondita Rob. ex desm. f. sp. tritici) in the Southern Steppe of Ukraine

Apart from making farmers adapt agricultural technologies to new, more arid conditions in order to obtain sustainable and high yields, global climate change is also known to alter the pathogenicity of plant pathogens, the biological cycle of which is tightly associated with environmental factors. One of the most common diseases of winter wheat is brown leaf rust, caused by Puccinia recondita Rob. ex Desm. f. sp. tritici. In terms of its harmfulness and prevalence among other leaf and stem diseases, brown leaf rust is comparable to yellow and stem rust, septoria leaf blotch and other leaves blotches. Under arid conditions of the Southern Steppe of Ukraine, the disease manifests itself once every five years provided that sufficient moisture, indicated by the hydro-thermal index above 1.0, is present during the spring and summer vegetation periods. The main factor influencing the intensity of pathogen development is moisture supply from April to June (ΣTP> 50 mm). In 2019, the amount of precipitation during this period was 194 mm, which led to the disease development at the level of 18.4% with a spread of 27.2%. Productivity of winter wheat varieties such as Antonivka, Blago and Maria was reduced by 10.8-11.3%, when infected in the phase of milk grain stage (stages 73-77 on the BBCH scale), while net photosynthesis productivity decreased by 14.2-14.3%, which translates to lower average yields of 2.3-3.1 t/ha. To maximize the productive potential of varieties and effectively control the development of the causative agent of brown leaf rust in winter wheat under favourable conditions for epiphytic development, the application of systemic fungicides with long-term protective effect imparted by the chemical group of triazoles (Colossal e.c., 1.0 l/ha ) is recommended in stages 69-71 on the BBCH scale. This provides not only reliable crop protection (Eff.: 77.9-82.0%), but also yields at the level of 3.3 - 4.6 t/ha, depending on the variety under non-irrigated conditions.

Biological control of olive anthracnose

Olive anthracnose, a fungal disease caused by species of the genus Colletotrichum, is responsible for severe yield losses and poor oil quality. Typical symptoms appear in autumn or early winter, when the drupes begin to ripen. Under favorable conditions, symptoms on branches and leaves can also occur, leading to chlorosis, severe defoliation, and death of woody organs. Symptomless infection of flowers and blights have also been reported. Latent fruit infections could play an important role as the inoculum source for the autumn-winter epidemics. Application of systemic fungicides has proved effective in field trials, and pre-flowering sprays contribute to reduce latent infection and the inoculum density for autumn infection. However, public concerns about potential risks on the environment and human health promoted the search for alternative and sustainable means. Therefore, the activity of a new sulfur-based product and biocontrol agents (Bacillus subtilis, and endophytic isolates of Aureobasidium pullulans) in reducing the incidence of olive anthracnose was evaluated under field conditions. The sulfur-based product and B. subtilis applied at the pre-flowering stage were as effective as the chemical fungicides in reducing the incidence of latent infections on drupes. Moreover, some endophytic strains of A. pullulans provided high protection levels against Colletotrichum spp. when applied at the pre-flowering and veraison stages. Overall, data indicated that olive anthracnose can be controlled by using biological means and new products could be considered for introduction in the list of the organic product specification.

Epidemiology and strategies for chemical management of powdery mildew in mango

Abstract: The objective of this work was to evaluate phytosanitary strategies for the chemical control of powdery mildew (Oidium mangiferae) in mango, based on the alternation of active ingredients with different modes and sites of action, and to determine the environmental and epidemiological conditions that favor the development of the disease. The experiment was conducted in Guerrero, México, in commercial orchards, within a program for the development of fungicide spraying strategies. Epidemic curves were used on temporal analyses of the disease for: incidence; area under disease progression curve (AUDPC); severity; and conidial seasonality and its relationships with meteorological parameters. The disease was better controlled with the application of systemic fungicide followed by contact fungicide with multisite activity. The first symptoms appeared 30 days after the issuance of shoots, and the most susceptible phenological (critical) stages were at full bloom and at the onset of fruit with 8-15 mm. Optimum conditions for the development of powdery mildew, which maximizes the density of airborne spores, are temperatures higher than 30°C and relative humidity over 90%.

Pengendalian Colletotrichum spp. Terbawa Benih Cabai dengan Paparan Gelombang Mikro

Seed treatment using microwave has been reported as an effective and efficient method to control seed borne pathogens of chili pepper. The purpose of this research was to evaluate the effectiveness of microwave irradiation treatment to suppress seedborne Colletotrichum spp. while maintaining physiological quality of chili’s seed. First experiment was aimed to select the best condition for seed germination, and was done in completely randomized design with three levels of water content (4.31%, 6.33%, and 8.25%). The second experiment was aimed to determine the best condition for disease suppression, and was done in completely randomized design with different levels of microwave irradiation duration (0, 10, 20, 30, 40, and 50 seconds) using the best seed water content level from the first experiment. Application of systemic fungicide with benomyl as active ingredient (0.5 g L-1) was done as check treatment. Four major species of Colletotrichum was found from chili’s seed, i.e. C. acutatum, C. capsici, C. gloeosporioides, and Colletotrichum sp. with C. acutatum as the predominant species. The best water content level for microwave treatment was 4.31%. The most effective treatment was microwave irradiation duration for 40 seconds with efficacy rate of 64.5% for controlling seedborne C. acutatum on chili pepper.

Analysis of the CYP51 gene and encoded protein in propiconazole‐resistant isolates of Mycosphaerella fijiensis

Mycosphaerella fijiensis Morelet causes black sigatoka, the most important disease in bananas and plantains. Disease control is mainly through the application of systemic fungicides, including sterol demethylation inhibitors (DMIs). Their intensive use has favoured the appearance of resistant strains. However, no studies have been published on the possible resistance mechanisms. In this work, the CYP51 gene was isolated and sequenced in 11 M. fijiensis strains that had shown different degrees of in vitro sensitivity to propiconazole, one of the most widely used DMI fungicides. Six mutations that could be related to the loss in sensitivity to this fungicide were found: Y136F, A313G, Y461D, Y463D, Y463H and Y463N. The mutations were analysed using a homology model of the protein that was constructed from the crystallographic structure of Mycobacterium tuberculosis (Zoff.) Lehmann & Neumann. Additionally, gene expression was determined in 13 M. fijiensis strains through quantitative analysis of products obtained by RT-PCR. Several changes in the sequence of the gene encoding sterol 14alpha-demethylase were found that have been described in other fungi as being correlated with resistance to azole fungicides. No correlation was found between gene expression and propiconazole resistance.

Control of loose smut (Ustilago nuda and U. tritici) infections in barley and wheat by foliar applications of systemic fungicides

Foliar application of a number of broad-spectrum systemic fungicides (particularly conazole fungicides) to loose smut-infected plants of wheat and barley in a 3-spray programme resulted in a marked reduction in the percentage of plants producing infected ears. Such foliar fungicides may have a previously unseen role in reducing the levels of loose smut infection in wheat and barley.

Downy mildew of Cucurbits (Pseudoperonospora Cubensis): the Fungus and its hosts, distribution, epidemiology and control

Taxonomy of the genusPseudoperonospora, morphology ofPseudoperonospora cubensis (Berk, et Curt.) Rostow. and occurrence of its oospores, are described briefly. A list is presented of over 40 cucurbitaceous host species, representing about 20 genera, on whichP. cubensis has been recorded. Two or more races exist in Japan and the United States, but not in Europe or the Middle East. The distribution ofP. cubensis is widest on all continents on cucumbers (70 countries) and muskmelon (50 countries); onCucurbita and watermelons it extends to about 40 and 25 countries, respectively. P. cubensis may overwinter as oospores, though this seems rare, and on wild hosts or crops grown in the open or under cover. Airborne sporangia may also reach cooler countries from regions with mild winters. Apart from the leaf wetness essential for infection, the factors determining disease progress are: rate of foliage growth and physiological age of the host; amount of primary inoculum available, light, and the rate at which lesions necrotize. The interaction of these factors is described for early, mid-season, and late crops. Losses caused byP. cubensis depend on the growth stage at which the crop is attacked, and on the rate of foliage and pathogen development. Breeding has produced downy mildew resistant lines of cucumbers, used chiefly in the United States, and some resistant lines of melons and watermelons. The most important agricultural practices used to restrict downy mildew development are proper irrigation management and avoidance of sowing in proximity to infected crops. Success of control by protectant chemicals depends largely on proper timing of applications. Proximity of inoculum sources, hours of leaf wetness, age of crop, and irrigation practices are the principal factors that determine when to begin treatments. These factors and rate of leaf formation determine the frequency of applications. Application of systemic fungicides is much easier to time correctly.

Effects of soil applications of systemic fungicides on bulb formation in onions

The effects of five systemic fungicides on bulb formation in onions were investigated. Bulb formation was decreased by repeated soil drenches of Sistesan, Bavistin and Plantvax: the decrease in bulb diameter was 40%, 22% and 14% respectively; bulb fresh weight was decreased by 61%, 32% and 27.5% respectively and bulb dry weight by 62.5%, 41%, 28%. Afugan and Saprol had no significant effects.