Management of Deleterious Effect of Fusarium oxysporum Associated with Red Palm Weevil Infestation of Date Palm Trees

Red palm weevil (RPW) is a dangerous pest that infects the date palm tree and makes tunnels in the tree’s trunk. RPW infection is followed by secondary invaders of microorganisms that cause degradation of the trunk tissues leading to toppling the crown and death of the tree in a short time. This study showed that Fusarium oxysporum Schlecht. was the common fungal species isolated from the root and trunk tissues of the date trees infested with RPW, which recorded 100% of frequency. Pathogenicity of 4 isolates of F. oxysporum was confirmed on date palm seeds and seedlings. The results confirmed that all isolates involved in rot of the germinated seeds (40–100% incidence), root rot, and death of palm seedlings (20–100%) under artificial infection as well as degradation of date palm petioles. Application of 20 L/palm of systemic fungicide (Topsin) at 1% as foliar and soil drench of date palm for successive three times successfully reduced development of the deterioration and suppressed the growth of F. oxysporum. Interestingly this fungicide did not suppress the growth of Trichoderma viride Pers. So, our results recommend this fungicide to suppress the pathological and degradable activities of F. oxysporum during the integrated pest management of RPW on date palm trees.

Enhancing septoria leaf blotch forecasts in winter wheat II: model architecture and validation results

In precision agriculture, pesticides and other inputs shall be used precisely when (and where) they are needed. European Directive 2009/128/EC calls for respecting the principles of integrated pest management (IPM) in the member states. To clarify the question, when, for instance, fungicide use is needed, the well-established economic principle of IPM may be used. This principle says that pests shall be controlled when the costs of control correspond with the damage the pests will cause. Disease levels corresponding with the costs of control are referred to as control thresholds in IPM. Several models have been developed in plant pathology to predict when epidemics will occur, but hardly any of these models predicts a control threshold directly limiting their usefulness for answering the question when pest control is needed according to the principles of IPM. Previously, we quantified the temporal distance between critical rainfall periods and the breaking of the control threshold of Zymoseptoria tritici on winter wheat as being affected by temperature, based on data from 52 field experiments carried out in Luxembourg from 2005 to 2016. This knowledge was used to construct the ShIFT (SeptorIa ForecasT, https://shift.list.lu/) model, which has been validated using external data recorded between 2017 and 2019. Within the efficacy period of a systemic fungicide, the model allowed correct predictions in 84.6% of the cases, while 15.4% of the cases were predicted falsely. The average deviation between the observed and predicted dates of epidemic outbreaks was 0.62 ± 2.4 days with a maximum deviation of 19 days. The observed and predicted dates were closely correlated (r = 0.92, P < 0.0001). Apart from outliers, the forecast model tested here was reliable within the period of efficacy of current commercial fungicides.

Mefenoxam Sensitivity in US-8 and US-23 Phytophthora infestans from Wisconsin

The contemporary dominant clonal lineage of heterothallic Phytophthora infestans in Wisconsin, US-23, is classified as sensitive to the systemic fungicide mefenoxam and is of the A1 mating type. With the sporadic appearance of clonal lineage US-8, classified as resistant to mefenoxam and of the A2 mating type, there is a need for ongoing monitoring and characterization. Isolates of P. infestans collected from Wisconsin during the 2017 and 2018 growing seasons were tested for sensitivity to mefenoxam with discriminatory dose of 100 ppm. In 2017, both US-23 and US-8 were isolated. On average, isolates of US-23 were significantly more sensitive to mefenoxam than were US-8 isolates (P = 8e-04). There were significant differences in the sensitivity levels among the US-8 isolates (P = 2.02e-06), with a single isolate testing sensitive at 100 ppm of mefenoxam based on the one-way ANOVA. There were significant differences in the sensitivity levels among US-23 isolates (P = 3.75e-09), with two isolates showing resistance. In 2018 only US-23 was found, and isolates were tested for mefenoxam response at 0, 0.1, 1, 10, and 100 ppm. At 0.1 ppm, isolates showed significantly different levels of sensitivity (P = 2.1e-09), and a single isolate showed complete resistance. Isolates from both clonal lineages and years that exhibited moderate levels of resistance had greater variability among replicates. The phenotype of this multigenic trait comes through in the variability seen in isolates that are showing more resistance. Continued screening of P. infestans for mefenoxam sensitivity will help track the development and mechanism of resistance, as well as aid in development of best management approaches.

Seed Treatment With Systemic Fungicides: Time for Review

Pre-sowing seed treatment with systemic fungicides is a firmly entrenched practice for most agricultural crops worldwide. The treatment is intended to protect the crop against seed- and soil-borne diseases. In recent years, there is increasing evidence that fungicidal applications to manage diseases might inadvertently also affect non-target organisms, such as endophytes. Endophytes are ubiquitously present in plants and contribute to plant growth and development besides offering resistance to biotic and abiotic stresses. In seeds, endophytes may play a role in seed development, seed germination, seedling establishment and crop performance. In this paper, we review the recent literature on non-target effects of fungicidal applications on endophytic fungal community and discuss the possible consequences of indiscriminate seed treatment with systemic fungicide on seed endophytes. It is now well recognized that endophytes are ubiquitously present in all parts of the plant, including the seeds. They may be transmitted vertically from seed to seed as in many grasses and/or acquired horizontally from the soil and the environment. Though the origins and evolution of these organisms in plants are a matter of conjecture, numerous studies have shown that they symbiotically aid in plant growth and development, in nutrient acquisition as well in protecting the plants from abiotic and biotic stresses. Against this background, it is reasonable to assume that the use of systemic fungicides in seed treatment may not only affect the seed endophytes but also their attendant benefits to seedling growth and establishment. While there is evidence to indicate that fungicidal applications to manage plant diseases also affect foliar endophytes, there are only few studies that have documented the effect of seed treatment on seed-borne endophytes. Some of the convincing examples of the latter come from studies on the effect of fungicide application on rye grass seed endophyte AR37. More recently, experiments have shown that removal of seed endophytes by treatment with systemic fungicides leads to significant loss of seedling vigour and that such losses could be partially restored by enriching the seedlings with the lost endophytes. Put together, these studies reinforce the importance of seed endophytes to seedling growth and establishment and draw attention on how to trade the balance between the benefits of seed treatments and the direct and indirect costs incurred due to loss of endophytes. Among several approaches, use of reduced-risk fungicides and identifying fungicide-resistant endophytes are suggested to sustain the endophyte contribution to early seedling growth.

Minimizing Yield Losses and Sanitary Risks through an Appropriate Combination of Fungicide Seed and Foliar Treatments on Wheat in Different Production Situations

Among the fungal diseases that affect wheat in temperate growing areas, Septoria Leaf Blotch (SLB) and Fusarium head blight (FHB) result in yield and sanitary risk losses that could be minimized through appropriate fungicide applications. Furthermore, the request from policy makers and the food market to reduce the use of chemical pesticides in agriculture has driven research in the direction of performant defense strategies with a reduced spraying of pesticides. The aim of this study was to evaluate the effects of different fungicide programs on the control of SLB and FHB, as well as on the grain yield and deoxynivalenol (DON) contamination of common wheat. Field experiments were carried out in 2016 and 2017 in North Italy. Two seed treatments (conventional vs. systemic) and four combinations of foliar fungicide applications (untreated control, application at the end of stem elongation, at flowering, and a double treatment at stem elongation and flowering) have been compared, according to a full factorial design, under two agronomic conditions: plowing vs. minimum tillage. Foliar sprayings at the end of stem elongation were found to be more effective in controlling SLB, while a triazole application at flowering was found to be an essential practice to reduce the FHB and DON contents. The double foliar treatment led to significant benefits, albeit only in the production situations with the highest SLB severity (e.g., in the 2017 experiment, after ploughing and the use of a conventional seed treatment). The systemic seed dressing led to a higher and prolonged STB protection, with significant canopy greenness during ripening in all the production situations. In 2017, which suffered from high disease pressure, the seed treatment with systemic fungicide led to a significant increase in grain yield (+5%), compared to the conventional one. The combination of the systemic seed treatment and the triazole application at flowering guaranteed the highest control of both SLB and FHB, maximized grain yield, and minimized DON contamination. This study provides useful information that could be used to evaluate appropriate fungicide programs, based on a combination of seed and foliar treatments, for wheat yield and sanity in distinct SLB and FHB diseases pressure scenarios.

Paclobutrazol as a plant growth regulator

Plant growth regulators are chemical substances which govern all the factors of development and growth within plants. The application of plant growth regulators to crops modifies hormonal balance and growth leading to increased yield, enhanced crop tolerance against abiotic stress and improved physiological trait of crops. Paclobutrazol (PBZ) [(2RS, 3RS)-1-(4-chlorophenyl)- 4, 4-dimethyl-2-(1H-1, 2, 4-trizol-1-yl)-pentan-3-ol], is one of the members of triazole family having growth regulating property. The growth regulating properties of PBZ are mediated by changes in the levels of important plant hormones including the gibberellins (GAs), abscisic acid (ABA) and cytokinins (CK). PBZ affects the isoprenoid pathway, and alters the levels of plant hormones by inhibiting gibberellin synthesis and increasing cytokinins level and consequent reduction in stem elongation. When gibberellins synthesis is inhibited, more precursors in the terpenoid pathway accumulate and that resulted in the production of abscisic acid. PBZ is more effective when applied to the growing media and application on the growing medium would give longer absorption time and more absorption of active ingredient than foliar spray. The application of PBZ to crops is important in reducing plant height to prevent lodging and in increasing number and weight of fruits per tree, in improving the fruit quality in terms of increases in carbohydrates, TSS, TSS/TA and decreases acidity. It further reduces evapo-transpiration and decreases plant moisture stress by enhancing the relative water content of leaf area and develops resistance in the plants against biotic and abiotic stresses. In addition, it acts as highly active systemic fungicide and used against several economically important fungal diseases. In this review, the current knowledge and possible applications of PBZ, which can be used to improve the growth, yield and quality of crops, have been reviewed and discussed. The role of PBZ to mitigate the harmful effects of environmental stresses in crops is also examined. Moreover, various biochemical and physiological processes leading to improved crop production under the effect of PBZ are discoursed in detail.

Integrated protection system against progressive corn diseases

A biologized system of integrated protection against pathogens in corn crops is an important feature to reduce pesticide load. The use of new generation chemical fungicides with a low consumption rate and a wide spectrum of action against dominant infections, as well as their manufacturing application, will contribute to the improvement of corn agrocenosis. Due to the predicted, and subsequently planned yield, the phytosanitary situation will help in the development and implementation of effective protective measures to obtain biologically cleaner production of corn grain. Seed disinfection only solves the problem of seed infection. The appearance and harmfulness of boil smut also occurs during the growing season. Therefore, the transmission of primary infection occurs by plant residues and airborne droplets, which suggests the possibility of a systemic fungicide response to effectively contain not only the causative agent of boil smut, but also other types of infectious diseases on vegetative and reproductive bodies of corn. Investigations carried out in 2018-2020 to reduce the harmfulness of blister smut and fusarium head smut showed that seed infections are caused by a pronounced prevalence of diseases of roots, stalks and ears, such as fusarium, boil smut, alternaria, bacterial leaf burn, etc. The resistance degree of cross-breeds to dominant diseases depends on the infection terms, weather and climatic conditions and which corn body is more susceptible to these pathogens. Considering the possibility of infection penetration during the post-emergent period of corn development it is required to use system fungicides with a low consumption rate and prolonged action. In the Kabardino Balkarian Republic, the dominant corn disease is boil smut. It is known that the harmfulness of boil smut is higher with cob forms than with stem, leaf forms of infection, but in 2020 only the cob form of the disease was recorded, the dry and hot weather was the reason for this. In the steppe zone of the Kabardino Balkarian Republic, it is more expedient to use effective fungicides in the developed complex protection of corn crops against progressive harmful bodies.

Efficacy of Different Level of Systemic Fungicides on Management of Rice Blast at Baitadi, Nepal

Rice blast (Pyriculariaoryzae Cavara) is one of the most devastating diseases affecting the rice crop in across the world. Systemic fungicides are used for the suppression of blast diseases caused by fungal pathogens. Propiconazole and Carbendazim are commercial chemical control products available in markets for the control of the fungal pathogen. An experiment was conducted to examine the effectiveness of systemic fungicide on suppression of rice blast incidence in farmers' field during wet seasons in 2016. The treatments consisted of the use of different levels of propiconazole and Carbendazim on ‘Rato Basmati’ a landrace rice variety. The experiments were arranged in a randomized complete block design with three replications. The disease was scored according to the standard scale developed by the International Rice Research Institute (IRRI). Disease severity and Area under Disease Progressive curve (AUDPC) was computed based on that scale score. Propiconazole and Carbendazim at different levels reduce disease development than no treatment (control). But its efficacy was not consistent. The magnitude of disease suppression by Propiconazole was high as compared to Carbendazim. The application of propiconazole at the rate of 1.5 ml effectively reduced disease severity and AUDPC at different dates. So propiconazole at the rate of 1.5 ml thrice at weekly intervals is effective to reduce the disease development

FUNGICIDES USING AGAINST LATE BLIGHT OF TOMATOES IN THE CONDITIONS OF TOPKINSKY DISTRICT OF KEMEROVO REGION

The article presents the results of field experiments in 2018-2019 on the influence of fungicides on the spread of late blight on tomatoes in the soil and climatic conditions of Topkinsky district of Kemerovo region. A comparative assessment of a broad-spectrum copper-containing fungicide Abiga-Peak and a contact-systemic fungicide Profit gold effect on five varieties of salad tomato and a universal one included in the state register for growing in the open ground, such as Volgogradets, Novichok, Novichok pink, Demidov and Denezhny meshok. The calculation of biological effectiveness of drugs is given under favorable conditions for growing tomatoes and forming high-quality fruits during the growing season 20182019. During 2018, the average monthly air temperatures 1.1-1.2 times exceeded average annual ones, in 2019, the average monthly air temperatures did not differ from average annual ones, and the amount of precipitation was uniform in both years of research. The comparative assessment showed that the lowest rates of late blight spread were found in the Moneybag (8.9%) and Novichok (10.7%) varieties using the Abiga-peak fungicide, and in the Moneybag (7.1%) and Demidov (9.8%) varieties using the Profit gold fungicide. The used fungicides were able to stop the intensity of late blight spread by 10-20% compared to the control variant. The calculation of biological effectiveness of the preparations showed that the best results were for the Profit gold fungicide on the Moneybag variety (64.3%) at the time of liquid harvest, and for the Abiga-Peakfungicide on the Novichok variety, showing a biological efficiency of 60.7%.