Fungal Diseases Integrated Management in Agriculture

Nowadays, fungal diseases play an essential role in the integrated management of agriculture. Integrated disease control includes multiple strategies and a complex approach based on knowledge of pathogens, plants, agronomy, and the interaction between them. Fungal diseases compromise the environment, pathogen virulence, and plant–host interactions. Agricultural practices, such as pesticide application, soil tillage, amount of infection materials, and climatic and other factors, influence the development of diseases. Geographically, plant pathogens have almost no borders due to plant material distribution or human mobility patterns. Understanding biological diversity, resistance, agronomic practice, disease warning and forecasting models, and biological fungicides, and the sustainable use of fungicides and the education of farmers are all essential to integrated disease control.

This Special Issue of Integrated Management of Fungal Diseases in Crops covers a wide range of topics inculding the biology and toxins production of Botrytis cinerea, identification, management, and adverse effects of Fusarium spp., and covers the screening of new Rehmannia glutinosa pathogens and the characterization of fungicide inhibitory effects. It also covers a Phytophthora cajan management plan for various fungicides and application methods and evaluates different fungicide and foliar fertilizer strategies for apple Venturia inaequalis control strategy.

Necrotrophic fungus B. cinerea, which causes grey rot disease, is an important pathogen, causing substantial economic losses to various floral and horticultural crops. Botrytis genera consists of more than 30 different fungal species. In addition, B. cinerea synthesizes phytotoxins as botrydial and dihydrobotrydial [1]. Toxic compounds of botanic and botrycineric acids and their cyclic derivatives cause plant cell collapse and chlorosis. In addition, botrydial is mainly a pathogenicity factor [1]. B. cinerea genetic variation within the population has significant physiological and morphological diversity [1]. In vineyards in Spain, B. cinerea predominated and distributed normal aggressiveness on leaves. These isolates belong to the mycelial type and both mating types [2]. The Lithuanian B. cinerea genetic variation analysis revealed that most isolates were sensitive to the fungicide fenhexamid [3]. Results revealed that B. cinerea B459 produces fewer reactive oxygen species (ROS) than B05.10. In addition, B05.10 lacks toxin production. However, both isolates demonstrated completely different capacities to infect and colonize different plant tissues. Additionally, both isolates reveal growth rate, fungal biomass, and nutrient utilization differences [1]. The study on B. cinerea toxin production and B05.10 and D459 isolates growth parameters, nutrient utilization, and differences under stress conditions, which could promote pathogen survival in dry environments. Differences between isolates help us to understand the B. cinerea mode of action in the field. Botrytis is quite essential for wine production, and it would be good to understand and adequately manage it [1].

Other important fungi, such as Fusarium spp. causes cereal [4] and other wide-range crop diseases due to mycotoxins. Fusarium spp. produces large and diverse pathogenic fungi families that produce mycotoxins mainly before harvest. Fusarium species are described as hyaline, septate, elongated, and slightly curved macroconidium. Usually, they have three to five septate [5]. The toxins produced by Fusarium spp. are mostly trichothecenes, fumonisins, and zearalenone [5]. The mycotoxin distribution depends on the host plant species, meteorological conditions, and Fusarium spp. strain [6]. Fungal identification is traditionally performed using morphological characteristics. However, the most precise identification nowadays is based on genetic tools [5]. The study of Fusarium spp. identification, adverse effects, management, and global security not only high-lights molecular tools as the most powerful tool for identification, but also provides an overview of the impacts on food security. We can only select the best management methods by fully understanding which fungal species we are dealing with. Fungal diseases are of economic and international significance for global food security [5].

Rehmannia glutinosa, an essential perennial herbaceous plant, is cultivated in Asia. The tuber roots or R. glutinosa used in medicine contain iridoid and phenylethanol glycosides and polysaccharides [7]. Diseases caused by Fusarium proliferatum and Rhizoctonia solani result in R. glutinosa stem and root rots. Additionally, Phoma herbarum and Ascochyta molleriana cause ring rot in bottom leaves. Alternaria alternata causes brown spots on leaves [7], or the primary symptoms are browning or rots. In addition, new pathogens could also be mixed up with other diseases. To manage the disease, you should first know the pathogen. Therefore, molecular diagnostics help [7]. As fungicides could cure or prevent disease, knowing if your object is causing crop diseases is essential for precise management. Not all fungicide’s active ingredients work on all pathogens. The molecular identification showed that R. glutinosa was infected by F. equiseti, which is quite a new pathogen for this perennial herbaceous plant [7].

Cajanus cajan perennial legume contains high levels of proteins and amino acids. It is widely cultivated in South and Southeast Asia, Africa, and Latin America. Phytophthora cajani is an important pathogen causing phytophthora blight [8]. Changes in P. cajani virulence, pathogenicity, or meteorological conditions have increased the severity of this pathogen. It is essential to know the effect of fungicides on mycelial growth, sporangia, and zoospores, as well as on seeds and seedlings [8]. The application method of fungicides through seed treatment, soil drenching, or foliar spray gives a lot of answers using chemical pesticides [8]. The primary strategy in plant protection is good agricultural practices, good quality seeds, and planting material. The European Union Directive 2009/128/EC promotes the sustainable use of pesticides and integrated plant protection (IPM). In addition, the EU promotes the use of low-risk biological-origin pesticides [9], even though sustainable pesticide use, and plant disease should be controlled due to pathogen harm to the crop and its yield. Considering C. cajan is a significant pathogen, P. cajani control works with broad-spectrum fungicides, inhibiting sporangia, zoospore germination, and mycelial growth [8].

Venturia inaequalis is one of the most essential apple scab-causing pathogens. The control methods of V. inaequalis consist of breeding programmes, resistant cultivars, and the use of fungicides [10], due to the EU’s recommendations and regulations to reduce the risk of chemical pesticide use and use less hazardous substances [9]. Much of the research is on the reduction in fungicide resistance risk by using inorganic fungicides and foliar fertilizers to control apple scab. Inorganic substances like lime and wettable sulphur, copper-based fungicides, are typically considered to have no risk of developing fungicide resistance. However, sulphur-based substances can damage the visual appearance of leaves and fruits [10]. Despite this, V. inaequalis could be controlled by inorganic fungicides in low-inoculum orchards. A combination of inorganic and synthetic fungicides reduces resistance development [10].

In the hopes of understanding pathogens and their control methods and measures to obtain high-quality production, this Special Issue of Integrated Management of Fungal Diseases in Crops contains a total of five research papers and one review paper. The papers were submitted from South Africa, Italy, China, India, Spain, and Lithuania.

In conclusion, fungal pathogens are not separable from integrated plant protection. We must identify plant diseases morphologically and molecularly and find solutions for their management.