Organic farming to mitigate biotic stresses under climate change scenario

Abstract

Background

Climate change is inevitable owing from modern-day chemical agriculture, exerting detrimental impacts on sustainable crop production. Global agriculture is now facing serious threats from biotic stresses like weeds, pests, diseases, etc. These stresses not only hamper growth and production but also reduce crop quality.

Main body of the abstract

Exclusive reliance on synthetic inputs to tackle biotic stresses has created resistance, resurgence, residues, etc., leading to environmental pollution. Although plants adopt defensive mechansims, such biotic stresses need to be addressed properly with various eco-friendly organic farming approaches. Suitable modification and adoption of various organic agronomic practices (manual, mechanical, cultural, and biological) such as soil solarization, crop rotation, intercropping, tillage, sowing time and method, nutrient, water and intercultural operations, organic formulations, selection of resistant/tolerant varieties, etc., can mitigate the negative impacts of biotic stresses to a high extent resulting in uplift in crop production as well as the quality of produce. Microorganisms not only alter soil health positively for high crop production but also alleviate biotic stresses through bio-stimulant properties. Various indigenous technical knowledge approaches show great promise to tackle biotic stresses further.

Short conclusion

Adequate research, integration of multiple technologies, build-up of awareness, etc., are the keys for successful organic plant protection under changing climate scenario.

Background

Various stresses in agroecosystems, both abiotic (temperature, water, sunlight, wind, salinity, nutrients, etc.) and biotic (bacteria, fungi, viruses, parasites, insects, weeds, etc.), have a significant impact on the quantity and quality of global agricultural production (Manghwar and Zaman 2024). This situation is exacerbated by shifting environmental factors such as climate variability, fluctuating temperature patterns, changing rainfall frequencies and intensities, and recurrent droughts, leading to a decline in biodiversity, increased incidences of pest, weed, disease infestations, etc. (Skendžić et al. 2021). Plants are vulnerable to several biotic stressors and unfavourable environmental conditions that can affect their morphological, biochemical, and molecular processes. ‘Biotic stress’ refers to the damage that plants suffer from living organisms such as pests, parasites, bacteria, fungi, nematodes, insects, and viruses (Nawaz et al. 2023). According to Yaman and Kumar (2021), biotic stress can lead to yield losses of 28.2% in wheat, 37.4% in rice, 31.2% in maize, 40.3% in potatoes, 26.3% in soybeans, and 28.8% in cotton. In order to prevent productivity losses, agriculture must be able to deal efficiently with biotic stressors. Plants create a variety of defence mechanisms to adapt to these conditions and survive (Zhang et al. 2024). They recognize the environmental stressors, become activated, and then produce the necessary biological responses. However, in most cases, these defence mechanisms alone are insufficient and requires external strategies to cope up with stresses. Chemical fungicides, herbicides, and insecticides that effectively control diseases, weeds, and pests have shown to be harmful to the environment and to human health (Pathak et al. 2022). In addition to their accumulation in other environmental components, the use of chemicals also leads to the mortality of non-target organisms (residual impacts). For instance, herbicides are more successful in eradicating uncommon plant species than weed species (Gaba et al. 2016). To reduce the use of pesticides, safer alternatives must therefore be used.

It is worthy and high time to replace chemical-based agriculture with low-cost or no-cost, ecologically sustainable methods of organic farming, taking into account the growing concern about climate change (Biswas et al. 2024). Organic farming eschews the use of synthetic chemicals, instead relies primarily on manual, mechanical, cultural, and biological strategies to address biotic stresses, which is a particularly important in the context of climate change (Ghosh et al. 2021). Climate change has brought with it a major challenge that many minor biotic stresses are now becoming major ones and therefore, continuous modification, integration of existing strategies, etc., are extremely crucial to achieve effective crop protection (Biswas and Das 2023). Currently, there is an increasing demand for organically grown food worldwide. To maintain supply parity, organic crop cultivation requires the implementation of environmentally sustainable insect, disease, and weed management techniques. This review discusses some of these important ecologically safe organic farming strategies to mitigate biotic stresses in order to limit yield losses due to these stresses under climate change conditions.

Major biotic stresses affecting crop production

At any stage of their life cycles, including seedling establishment, plant development, or grain or fruit setting, crop plants are susceptible to attack from various biotic stresses highlighted hereunder.

Diseases

The invasion of pathogens by fungi, bacteria, and oomycetes exemplify biotic stressors. Worldwide, diseases caused by these pathogens stand as a principal driver of yield diminishment. Together with other aspects of global change, such as anthropogenic activities like air, water, and soil pollution, the introduction of alien species over long distances, urbanization, and drought, pathogens can be directly affected by climate change and thereby, influence plant diseases (Muluneh 2021). The negative consequences for the spread of viral diseases to new areas arise from global warming which increases the range of virus-transmitting insects, the globalization of agriculture, and international trade in seeds and seedlings (Jones 2021). Fungal diseases are ubiquitous in agriculture (Shukla et al. 2022). In addition to fungi, other microorganisms such as bacteria, virus, protozoa, etc., can damage seeds, cause root rots, and induce leaf spots, plant wilt, and other diseases in plants.

Insect pests

Insect pests, nematodes, etc., are significant biotic stresses in agriculture, and can cause considerable damage to crops, leading to declination in yields and economic losses (Nawaz et al. 2023). They also act as vectors of pathogens. The most important biotic stressor behind crop losses worldwide is insect pests. The amount of dry matter eaten by pests determines the direct losses, and contaminated processing products and damaged kernels cause the indirect losses (Berhe et al. 2022). Insect pests are highly adaptable in intentionally modified environments where crops are selected for their growth, productivity, and nutritional value and arranged in limited areas (Jankielsohn 2018). Insect pest management is critical for ensuring food security and the sustainability of agricultural systems.

Weeds

Indeed, weeds are considered as major biotic stresses in agriculture, as they compete with crops for important resources such as nutrients, water, and sunlight (Monteiro and Santos 2022). Monocropping exacerbates weed proliferation and often serves as a breeding ground for crop pests and pathogens (Kumar et al. 2021). Their seeds spread via air, water, birds, insects, human beings, livestock manures, agricultural equipments, etc. Climate change leads to significant losses in crop productivity, including weed flora shift, weed invasion into new areas, weed resistance to chemical herbicides, persistence of weed seed banks, etc. (Anwar et al. 2021). Weed control is, therefore, crucial for maintaining crop health and maximizing yields.

Organic ways to mitigate biotic stresses

The use of numerous technologies, such as mulching, multiple crops, flowering and nectar plants, trap crops, and cover crops, can effectively control many biotic stresses (Jeer et al. 2021). Careful and continuous monitoring of pest and disease infestations at critical stages of a crop's growth is key to efficient management. The farmer can achieve this by conducting regular zigzag field observations. There are many ways to combat biotic stresses (Fig. 1).

Fig. 1

Biotic stress management options

Physical and mechanical methods include the use of traps, baits, manual, and mechanical options to control the biotic stresses. For instances, manual collection of insects and larva, uprooting plants and destroying diseased parts, clipping off of the pest and disease infested leaves, hand weeding, hand hoeing, wheel hoeing, spudding, digging, chaining, flaming/burning weeds, soil solarisation, etc., all play a role in reducing biotic stresses (Rana and Rana 2019).

Cultural control is about modifying the environment, improving the health of host, or modifying the pest's behaviour to mitigate or prevent infestation. Crop rotation, crop and variety selection, sowing time, spacing, seed rate, time of harvesting, irrigation and nutrient management, tillage, mulching, intercropping, stale-seedbeds, summer fallow, and the use of trap crops all contribute to reducing populations of weeds, pathogens, insects, mites, and other pests in agricultural crops (Shekhar et al. 2024). It can be important to plan and select practices in advance, as certain cultural practices are preventive rather than curative (El-Shafie 2019).

Biological control includes the use of living organisms (bioagents such as predators and microorganisms) as well as plant products which can be successfully used against biotic stresses (He et al. 2021). It is important to emphasize that a single strategy is insufficient in most cases. A combination of mechanical, cultural, biological, and physical methods may be required to successfully reduce biotic stresses (Angon et al. 2023). Some common approaches to mitigate biotic stresses in organic agriculture are described below.

Soil solarization

Soil solarization is an effective ecological method to control weeds, soil, or seed-borne insect pest issues by covering the soil with a transparent polythene film. In a study conducted by Wada et al. (2024), soil solarization reduced the weed emergence by 67–96%. The radiant heat generated by solar radiation under a polyethylene film effectively kills insect and nematode pests at temperatures of 45–50 °C, penetrating to a depth of 5–6 cm within the soil. For effective crop yield and long-term pest control, it can be used in conjunction with other techniques such as mulching and organic amendments. Numerous plant-parasitic nematodes (PPN) are successfully controlled, including the root-knot nematode (Meloidogyne spp.) (Abolusoro et al. 2020), spiral nematodes (Helicotylenchus spp.) (Abd-Elgawad 2020), reniform nematodes (Rotylenchulus reniformis) (Shi et al. 2023), cyst nematodes (Heterodera spp. and Globodera spp.) (Mokrini et al. 2017), etc. Soil solarization effectively controls the major parasitic fungi and diseases such as damping off, root rot, stem rot, fruit rot, wilt, and blight caused by Pythium spp., Phytophthora spp., Fusarium spp., Sclerotia rolfsii, Rhizoctonia solani, Sclerotinia sclerotiorum, and Verticillium spp. It also successfully controls a variety of bacterial and fungal pathogens in soil, including Agrobacterium tumefaciens, Macrophomina spp., Phytophthora spp., Verticillium spp., Rhizoctonia spp., and Pythium spp. (Gill et al. 2017). Dwibedi and Dwibedi (2020) and Omotayo and Eegunranti (2023) observed that soil solarization effectively suppressed Fusarium wilt in guava and Ralstonia wilt in tomato, respectively. The fundamental process of soil solarization involves the use of plastic mulch to effectively trap solar radiation, increase the temperature of the soil surface, and destroy unfavourable soil microbes. Although it has no discernible effect on other soil chemical parameters, soil solarization lowers the pH, microbial respiration, microbial biomass, and concentrations of potassium (K), sodium (Na), boron (B), and zinc (Zn) in the soil. The heat generated by soil solarization plays an important role in reducing the population of microbes which cause crop wilts (Yuliar et al. 2015). The effectiveness of soil solarization in controlling weeds, nematodes, and black root rot in strawberries has already been demonstrated by Abd-Elgawad et al. (2019).

Crop rotation

Another environmentally friendly agronomic technique for coping with many biotic stresses in the soil ecosystem is sequential cropping or crop rotation. For a plant to thrive, living organisms must interact with their environment. Monocultures pose a greater threat to a plant's health, while on-farm crop rotation promotes a balanced relationship among various plants, pests, and predators. The basic principle of sequential cropping is the rotation of non-host plants to counter certain biotic stresses. Crop rotation influences the microclimate, necessary for many weeds to germinate and develop (de la Fuente et al. 2021). As a result, most weeds associated with crops disappear on their own. Since biotic stressors are usually specific to a single crop, an appropriate cropping system can be crucial to suppress them. In one study, a diversified crop rotation led to coping with biotic stresses and increased spring wheat production by up to 30% compared to monoculture (Jalli et al. 2021). Similarly, Volsi et al. (2022) confirmed the effectiveness of crop rotation in coping with biotic stresses, as they achieved high system productivity in a maize–soybean rotation through species diversification. Some instances of management of biotic stresses through crop rotation are shown in Table 1.

Table 1 Management of biotic stresses through crop rotation

Crop diversification

Crop growth can be increased by crop diversification, increasing competitiveness and weed tolerance. Diversely planted and harvested crops can prevent or lessen the growth of weeds and the formation of weed seeds. Due to their distinctive characteristics, weeds flower at certain times of the year. The weed problem can be solved by modifying the crop, which prevents the weeds in question from spreading. Controlling weed infestations has an indirect effect on the regulation of pests and diseases, as these weeds often serve as hosts for pests and pathogens (Dentika et al. 2021).

Stale seedbed technique

The stale seedbed technique (also known as false seedbed preparation) is a suitable option for controlling problematic weeds in the field. According to a study by Benvenuti et al. (2021), the weed seed bank investigation (10–30 cm) revealed that no depletion of weed seeds was observed beyond 10 cm soil depth, suggesting that buried seeds were unaffected by tillage methods beyond 10 cm soil depth.

In contrast, the germination stimulus induced by soil aeration and the associated increase in oxygen availability after tillage significantly reduced the weed seed bank in the shallowest soil layer (0–10 cm). When limiting variables for seed germination, such as oxygen, light, and soil-seed contact are present in the case of weed seeds deposited on the soil surface, seedbed preparation triggers germination of a portion of the weed seed bank (Boyd et al. 2006). In the stale seedbed method of weed control, soil disturbance is minimized and the toxic effects of herbicides can be prevented by allowing the weed seeds that are just below the soil surface to grow before they are killed and thereby, sowing the crop. The idea behind the stale seedbed method is that weeds that germinate and become visible before the crop sowing are easier to control. Here, the seedbeds are prepared and the weeds are encouraged to germinate by irrigation or rainfall. Thereafter, weeds are manually or mechanically suppressed prior to crop cultivation. Before sowing, the removal of freshly germinated weeds by harrowing with a blade harrow is very effective. The first one to two flushes of weeds are removed by harrowing before planting or sowing the crop (Senthilkumar et al. 2019). This method as a part of integrated weed management is very effective in annual or seasonal weed control of major field crops, vegetable crops, etc. Nalayini et al. (2023) reported effective weed suppression in irrigated cotton by using legumes like Vigna unguiculata and Crotalaria juncea in the seedbed.

Growing resistant varieties/competitive crop cultivars

Breeding resistant varieties/competitive crops is of greater importance as it has been observed in many cases that biotic stresses are often accompanied by abiotic stresses due to climate change (Guzmán et al. 2022). In organic farming, effective plant breeding techniques to develop suitable (resistant/tolerant) crop varieties can be instrumental in reducing the impact of biotic stresses such as pests and diseases (Ui-Allah et al. 2023). In a study, Padmavathi and Padmaja (2022) referred to the antixenosis, antibiosis, and tolerance mechanisms of the crop in combating biotic stressors. All three rusts of wheat have shown to be resistant to the cultivar 'PBW 343'; the cultivar 'Rewena' is resistant to apple scab; and the cultivars 'HD-29', 'HD-30', and 'HP 1531' are resistant to Karnal bunt of wheat (Iquebal et al. 2021). Certain varieties are better adapted to the soil moisture, space, air, and light than weeds due to their weed tolerance and ability to suppress weeds. As a result, they develop faster, outcompete weeds, and yield a greater quantity of fruits and vegetables.

Seed treatment and preservation

Effective seed treatment plays an important role in the containment of soil and seed-borne pathogens and insects. According to Rajput et al. (2021), there are several diseases and pests that can be controlled by hot water or hot air treatment such as whip smut, grassy shoot and red rot of sugarcane (52 °C for 30 min), loose smut of wheat (52 °C for 10 min), and others. In addition, seed treatment with Trichoderma can mitigate rotting and other pathogens (Tao et al. 2015). The use of neem-based materials can also be effective. In natural farming, now-a-days, plant protection properties can also be demonstrated by treating seeds with Beejamrit, Beej Sanjeevani, etc. (Biswas 2020).

In organic farming, it is common practice to store the seeds for sowing in the next season/year. Proper preservation and storage of seeds can maintain the seed quality by warding off storage insects and diseases. Adequate hygiene, ventilation, disinfection, and regular monitoring are essential. Periodic drying of seeds can reduce moisture content and thereby reduce pathogens (Dadlani et al. 2023). Storing seeds in air-tight containers prevents the moisture absorption from humid air. Revitalizing seeds with neem-based materials, red chili powder, biochar, and similar substances can maintain seed quality over longer periods and repel biotic stresses (Das and Biswas 2022). Appropriate rat control measures should also be taken during seed preservation.

Soil management through nutrition and amendments

In conventional agriculture, the excessive use of nitrogenous fertilizers leads to an infestation of various insect pests. The formation of host metabolites, which can either prevent or promote infections by various pathogens, is also impaired by high nitrogen levels. If the roots are over-fertilized, subsequent diseases can develop due to salt damage to the roots. For instance, in crops grown in nitrogen-rich soils, the severity of rice blast (Magnaporthe grisea) and scald (Rhyncosporium oryzae) tends to increase, whereas maize head smut (Sporisorium reilianum) tends to infest less (Ghosh et al. 2021). Phosphate fertilization can increase the incidence of cucumber mosaic virus in spinach but reduce the incidence of potato scab (Streptomyces scabies) (Ghosh et al. 2021). Adequate potassium levels prevent the development of many different types of parasites, such as nematodes, bacteria (such as Corynebacterium nodusum and Xanthomonas sp.), fungi (such as Fusarium oxysporum f.sp. vasinfectum), and viruses (Do and Gries 2021). Adequate levels of calcium lead to increased resilience of cell walls against facultative pathogens such as Rhizoctonia, Sclerotium, Botrytis, and Fusarium. However, calcium-rich soils are conducive to the growth of diseases such as black shank of tobacco (Phytophthora nicotianae) (Pandey 2023). It is widely acknowledged that silicon enhances the ability of plants to withstand various biotic and abiotic stressors. Bakhat et al. (2018) reported that the plants of poaceae family exhibit the greatest capacity for silicon storage, followed by the cucurbitaceae and some solanaceae species. A variety of biotic stressors, such as root rot of cucumber and tomato, cucumber powdery mildew and chilli anthracnose, brown plant hopper, white-backed plant hopper, brown stem borer, leaf folder, green leaf hopper, stem maggot, leaf spider mites, root-knot nematode, blast disease of rice, wheat, and sorghum green bug, corn leaf aphid, sugarcane stalk-borer, and tomato wilt, can be controlled with silicon nutrition (Jeer et al. 2018). The incorporation of organic manure is essential for enhancing soil fertility and promoting optimal physical, chemical, and biological properties. This, in turn, fortifies plants against pests, diseases, etc. By supplementing the soil with organic amendments like sawdust, straw, oil cake, etc., Pythium, Phytophthora, Verticillium, Macrophomina, Phymatotrichum, and Aphanomyces infections can be efficiently managed (Rosskopf et al. 2020). Additionally, the utilization of neem, karanj, mahua, and other cakes can provide some level of control over soil-borne diseases and pests.

In organic farming, application of manures serves as an essential method for supplying nutrients to crops. Very often, it is witnessed that these manures spread diseases, insect pests, and weeds as the manures contain disease-causing pathogens, insect pests (adult, larva, eggs, etc.), and viable weed seeds (Yatoo et al. 2021). Therefore, a preventive approach and quality control measures should be implemented before usage. To mitigate the risks associated with manure application, it is imperative to ensure the proper breakdown of raw materials, eliminate any materials that may harbour disease-causing pathogens, insects or weed seeds, and conduct routine monitoring. When nutrients are applied, weeds tend to absorb a significant portion of these nutrients, leading to an increase in weed density and dry biomass accumulation (Kousta et al. 2023). According to Stewart et al. (2018), incorporating manure into the soil or using it as a sub-dressing can effectively suppress the growth of problematic weeds such as spotted spurge (Euphorbia maculate) and giant crabgrass (Digitaria sanguinalis).

Summer/deep ploughing

Soil dwelling pests such as nematodes and insects are driven off the field through regular soil disturbances during the summer (Kumar et al. 2020). Deep ploughing, combined with crop rotation and the use of biocontrol agents, can effectively control dry root rot and chickpea collar rot (Singh et al. 2018). This practice not only exposes insect larvae, eggs, nematodes, and pathogens to the sun's heat, but also reduces the viability of weed seeds due to increased solar radiation. Additionally, deep ploughing disrupts already established weeds and prevents them from setting seeds. Both annual and perennial weeds can be eliminated through deep ploughing in the summer by heating up the soil (Sharma and Rayamajhi 2022).

Irrigation methods

It has been evident that continuous flooding can significantly reduce the weed infestation from crop field through inhibiting weed respiration and creating anaerobic situation (Kaspary et al. 2020; Choudhary and Bhambri 2013). Low land paddy cultivation is, thereby, less infested from weeds than upland and aerobic paddy field (Liu et al. 2019). Specifically, flooding has been found to be particularly effective against grasses and broad-leaf weeds such as Cynodon dactylon, Alternanthera spp., Phyllanthus spp., Eclipta spp., and Commelina spp. Micro-irrigation is another method that can effectively inhibit weed growth by delivering water directly to the roots of crops (Kaur et al. 2020). Removing weeds from irrigation ditches is another way to prevent their proliferation.

Biological control

One effective and sustainable method for managing biotic stresses in agriculture is the use of biocontrol agents such as parasitoids, predators, insects, and microorganisms (Prajapati et al. 2020). Potential biocontrol agents for numerous plant diseases include Trichoderma sp., Azospirillum lipoforum, Gliocladium sp., Psuedomonas fluorescens, Bacillus subtilis, Aspergillus niger, Azotobacter chroococcum, etc. Pseudomonas fluorescens and Trichoderma spp. alone can stop 92% and 96% of infections, respectively, but a combination of the two can stop 97% of infections of Ralstonia spp. (Yendyo et al. 2017). Furthermore, El-Saadony et al. (2022) also highlighted the potential of plant growth promoting rhizobacteria as effective biocontrol agents against various fungal and bacterial diseases in crops. Organic farming, as opposed to conventional agriculture, is known for its greater arthropod fauna diversity and the preservation of natural enemies (El-Shafie 2019). In addition to biocontrol agents, there are numerous bioherbicides available for weed control, such as Collego, Devine, and Biomal, which are produced by microorganisms (Hasan et al. 2021). Most often, in addition to insects, weeds and other pests can be effectively suppressed by competing plants, smother crops, mites, fish, etc. (Patil et al. 2020). Some living materials used for plant protection in organic farming are shown in Table 2.

Table 2 Some materials used for plant protection in organic farming

Biofumigation

Biofumigation is a cutting-edge agronomic technology that utilizes non-chemical methods to combat biotic stresses such as soil-borne diseases, weeds, and insect pests (Rahman et al. 2021; Hanschen and Winkelmann 2020). This process involves introducing live plants of specific species into the soil, where they are chopped down to release organic volatile compounds that can effectively limit or eliminate these biotic stresses (Midzi et al. 2022; Gfeller et al. 2019). As biofumigants, the cruciferae family plants (Indian mustard, cabbage, cauliflower, and radish) can be used. Further, sorghum, marigold, and neem are few non-brassicaceae species that can be employed as biofumigants (Dutta et al. 2019). For instance, in mustard, when myrosinase is present, it forms glucosinolates, which when degraded release isothiocyanates to kill PPN (Brennan et al. 2020).

Plant biostimulants

Plant biostimulants derived from plant raw materials such as neem, karanj, and seaweed extracts, seed oils, and biomasses are recognized as effective tools for controlling plant-parasitic nematodes (PPN) and enhancing crop productivity (D'Addabbo et al. 2019; Ali et al. 2021). A study conducted by Rizvi et al. (2015) demonstrated that plant biostimulants containing sesame seed oil, neem biomass or seed meals, and quillay water extract effectively reduced populations of root-knot nematodes in tomatoes under greenhouse and field conditions. Additionally, research by La Spada et al. (2021) showed that post-harvest green mould caused by Penicillium digitatum in oranges could be suppressed by seaweed Ascophyllum nodosum and extracts from sugarcane and alfalfa. Similar to this, Kanatas et al. (2022) found that biostimulants had a beneficial effect on the control of noxious weeds.

Conservation tillage

In a certain agricultural habitat, conservation tillage promotes biodiversity, leading to increase in natural enemies along with insect pests (Jasrotia et al. 2023). However, with time, insect pests’ survival rate decreases. Minimal soil disturbance by conservation tillage usually encourages the activity of soil dwelling insect pests (Alyokhin et al. 2020). As opposed to conventional tillage, which offers food and shelter to the majority of the natural enemies, conservation tillage creates a more complicated habitat for a variety of arthropods (Lichtenberg et al. 2023). Jecobsen et al. (2022) noted an increase in soil dwelling arthropod predators as a result of mulching and reduced tillage in conservation agriculture (CA). These insects, which include predatory beetles, spiders, ants, wasps, and earwigs, are found in the micro- and meso-environment. Another benefit of no-till farming is the enhancement of microbial activity and efficient resource utilization (Chauke et al. 2022). A study by Li et al. (2020) demonstrated that maintaining stubble under no-tillage had a significant impact on soil microbial diversity by altering soil organic carbon and total nitrogen concentrations. The integration of no-till farming with crop diversity is crucial for ensuring the sustainability of global agriculture (FAO 2014).

Biopesticides

Biopesticides have emerged as a sustainable and environmentally friendly alternative to chemical pesticides, addressing concerns related to pathogen and pest resistance, the harmful effects of synthetic chemicals on human health, soil microorganisms, ecosystems, and the environment, as well as the increasing cost of traditional pesticides (Ayilara et al. 2023). Microorganisms, natural pyrethrins, rapeseed oil, and paraffin are most frequently employed as insecticides; copper compounds, sulphur, and microorganisms are most frequently used as fungicides (Dar et al. 2021). Organic agricultural standards allow the use of unregistered products such as nettle slurry, which is used to smother aphids on plants. This idea permits the use of foods like vinegar and sunflower oil as plant protection. Sunflower oil, whey, and lecithins are examples of fungicides; vinegar has bactericidal and fungicidal properties; and Urtica sp. has insecticidal and acaricidal properties (El-Shafie 2019). In organic farming, Dashparni is a plant-based compound that is now being widely utilized to control insect pests along with other formulations such as Neemastra, Agniastra, and Brahmastra (Kumari et al. 2022) (Table 3). Despite their potential benefits, biopesticides are currently underutilized due to limited farmer accessibility and a lack of authorized products, despite their ability to effectively control harmful diseases and pests (Mishra et al. 2020). Sincere efforts are required if they are to become widely accepted by the farmers.

Table 3 Ingredients and quantities for various bio-pesticide preparation

Biochar

Biochar is a valuable soil amendment produced through the controlled pyrolysis of organic materials at high temperatures (Amalina et al. 2022). The feedstock, temperature, pyrolysis conditions, and time all affect the quality of the biochar (Ippolito et al. 2020). Yang et al. (2022) demonstrated that the addition of biochar to soil not only increased plant biomass by 44.05% but also significantly reduced disease severity by 47.46%. Among different feedstock, biochar derived from straw has shown the strongest disease suppression capabilities. A global meta-analysis conducted by Iacomino et al. (2022) revealed that biochar can effectively reduce various soil pathogens and pests (86% of fungus, 100% of oomycetes, 100% of viruses, 96% of bacteria, and 50% of nematodes). Most studies used sawdust and wood waste as feedstock, with a range of application rates from 1 to 3% and a pyrolysis temperature of 500–600 °C. In addition to the detoxification of chemical agents, biochar can inhibit soil pathogens through various mechanisms, including (1) nutrient provision and improved nutrient uptake, which foster plant growth and resilience against pathogenic soil microbes; (2) microbe stimulation that directly inhibits soil pathogens through parasitism, competition, or antibiosis; and (3) biochar associated organic compaction. Furthermore, biochar has shown to suppress weed populations, as demonstrated in a study by Salman et al. (2020) where significant reductions in weed populations were observed in maize fields following biochar application.

Habitat management

The primary objective of tillage is to alter the soil's physical and chemical composition to make it more conducive to crop growth. By disturbing the soil, tillage effectively buries weed seeds deep within it, preventing them from germinating (Travlos et al. 2020). Additionally, it enhances aeration and removes entrenched perennial weeds. Conventional tillage methods are effective in eradicating weed flora from fields, while also reducing the density of wild weeds that struggle to thrive in cultivated environments. Weeds that grow between crop rows have their root systems disrupted by intercultural tillage. Moreover, tillage can directly kill insects through physical contact, malnutrition, exposure to predators, and adverse weather conditions. Furthermore, one of the simplest manual or mechanical pest management methods is hand-picking insects or weeds. Pests can also be physically or mechanically disrupted using techniques including mowing, hoeing, blazing, tilling or cultivation, and washing (El-Shafie 2019). Row coverings, safety nets with different mesh sizes depending on the pest, and sticky paper collars that stop crawling insects from climbing tree trunks are just a few of the tools that can be used in organic farming to keep insect pests from getting to crops. High-pressure water sprays can be used to eliminate insect pests such as mites and aphids from plant surfaces. Before transplanting rice seedlings, it is recommended to clip the leaf tips to remove stem borer egg masses (Adane 2023).

Utilizing cover crops or live mulches, such as annual or perennial plants grown before or after the main crop to cover the soil for a season or a year, can significantly enhance the diversity and abundance of natural enemies (Kahl et al. 2019). In a study, red clover (Trifolium pratense L.) was employed as a cover crop in cucumber to encourage the action of natural enemies and stop the spread of melon aphid and stripped cucumber beetle (Kumara et al. 2021). According to Fernando and Shrestha (2023), cover crops offer a viable alternative to tillage for weed management, particularly during the winter season when optimal cover crop establishment is feasible. Through allelopathic action, interspecific competition, and niche prevalence, cover crops effectively suppress weeds (Shan et al. 2023). By strategically placing dead or living things between crop rows to shield the exposed areas from sunlight, the likelihood of weed development and germination is reduced, thereby minimizing competition for essential resources. Mulch materials serve a similar purpose by lowering water evaporation and increasing soil moisture availability. Through the release of allelochemicals, mulch materials can impede the weed growth and development (Khamare et al. 2022). Furthermore, nectar-producing flower plants play a crucial role in providing additional sustenance, fostering development, and increasing activity among natural enemies. Numerous plants within the compositae family are particularly effective in attracting the diverse array of natural enemies, serving as valuable sources of supplementary food, and eventually, aiding in the suppression of insect pests.

Time, method, depth, and density of sowing/planting

Numerous cultural techniques, such as changing the sowing method, timing, depth, and spacing, can make a decisive contribution in mitigating or avoiding biotic stressors in agriculture. Every disease and pest has a peak time for infestation. The peak time of infection can be controlled by changing the sowing date. For example, the shoot fly (Atherigona soccata, A. naqvii) occurs less frequently and is less damaging when maize is sown early (Arshad et al. 2019). Aphid infestation in mustard is higher when sown later (Viradiya and Gangwar 2022). Smuts and seedling diseases caused by Fusarium sp. and Rhizoctonia sp. are more severe when seeds are sown deep (Kelly 2020). Similarly, if potato seedlings are planted too deep, Rhizoctonia can damage them more quickly (Potato News Today 2021). Sometimes, the incidence of disease can be reduced by dense stands, resulting in higher crop yields. Since fragmented ground cover in Africa attracts the aphid vector of groundnut rosette virus more than continuous ground cover, dense planting helps prevent the vector from landing (Ghosh et al. 2021). The direction in which seeds are sown in some row crops can also influence the development of certain diseases. A large number of seeds produces many more plants per unit area and reduces the space available for the establishment and growth of weeds. As a result, there is less weed growth in the fields. Increasing the seed rate in wheat from 75 to 125 kg/ha leads to a reduction in weed growth and an increase in crop yield by 20–26% (Khasraw et al. 2023). As some weed species only sprout and grow at certain times, and they can be easily controlled by adjusting the sowing window. In one study, earlier sowing of maize resulted in heavier infestations of Chenopodium album, Abutilon theopharsti, and Fallopia convolvulus than at the normal sowing time (Vidotto et al. 2016). Phalaris minor generally has a lower density in wheat sown earlier (in November), but a higher density in wheat sown later (in December), resulting in a lower seed yield (Singh et al. 2019). The configuration of crop rows can significantly impact weed infestation levels. Narrow rows tend to have fewer weeds due to increased competition for space, while wider rows often experience more severe weed infestations as there is more room and resources available. For example, a study by Choudhary et al. (2021) found that planting rice in narrow rows with a width of 15 cm resulted in reduced weed emergence and establishment, leading to lower dry weed biomass and increased grain productivity. However, it is important to note that closer spacing can also have drawbacks. Increased humidity in the microclimate created by closer rows can potentially lead to higher levels of pests and diseases, as highlighted by Singh et al. (2023).

Traps and trap crop

Various types of traps are utilized in organic farming to effectively control pests. For instances, light traps can capture armyworms, cutworms, stem borers, and other nocturnal insects (Akeme et al. 2021). Colour and water traps are employed to suppress adult thrips populations, while yellow sticky traps are effective in controlling white flies, aphids, and leaf-mining flies. Pheromone traps, fruit bagging, mechanical picking of eggs, adults, larva, etc., are also used to capture the insect pests (Thakur et al. 2021).

Growing a trap crop near or in the vicinity of the primary crop can attract or divert insect pests. Some of the trap crops act as attractants, enticing insect pests to lay their eggs there and lessening the pest burden on the primary crop. A classic example is planting marigold around the perimeter to attract Helicoverpa armigera (Kumar and Cheema 2020). To suppress the diamond back moth in crucifers, trap crops such as Indian mustard are planted in a 25:1 ratio (Reddy 2017b). Castor is grown as a border crop and groundnut as a trap crop along cotton borders to lessen the effects of tobacco cut worms. Cowpea is used in groundnut fields as a trap to control the red-hairy caterpillar. Cultivation of pearl millet or sorghum near cotton fields deters thrips and whiteflies. Desmodium is grown between maize to repel the stem borers (Erdei et al. 2024).

Indigenous technical knowledge (ITK) approaches

Indigenous technical knowledge (ITK) encompasses the collective wisdom and practices unique to a culture, derived from generations of experience in navigating life's challenges (Sow and Ranjan 2021). ITK is a practical body of knowledge rooted in a community that has developed it, been preserved, and been refined through many generations by close interaction, close observation, and experimentation with its environment. It is evident that diverse ITKs are employed to combat biotic stresses in various regions (Bolaji Umar et al. 2022). Some are highlighted in Table 4.

Table 4 Various ITK approaches to control biotic stresses

Intercropping

Intercropping, the practice of growing of two or more crops together in a same field with distinct row arrangements is a beneficial agro-technique which covers the vacant spaces remained between main crop rows and thus, suppresses weeds. Crops and weeds compete for nutrition, light, and space. Since there is plenty of room, it usually grows in between the two rows of crops. Weeds are unable to sprout and spread when intercrop takes over that area because intercrop competes with weeds for resources. Furthermore, it lowers the weed plant population by obstructing sunlight, which is one of the key elements for weed growth (Scavo and Mauromicale 2020). Research works have repeatedly demonstrated that intercropping is generally more successful than mono cropping systems in weed suppression. For example, when smother crops like forage legumes are interplanted with a primary crops such as cereals, the weed-suppression effect is particularly pronounced. When the main crop struggles to compete with weeds, intercropping with grain crops can be an effective weed-suppression tactic (Nath et al. 2024). According to a research by Omovbude et al. (2017), intercropping reduces weed density by 43.2–59.7% and effectively smothers weeds by 84.2%. Intercrops can comprise of plants that are hosts or non-hosts of a certain pest. Intercrops can include plants that either attract or repel pests, helping to reduce pest pressure on the main crop. Insect pests and nematodes that are drawn to the intercrop can be eliminated using alternative strategies, such as organic pesticides. Many intercrops also secret poisonous chemicals. Intercrops with allelopathic effects offer a powerful defence against weeds, nematode, insect pests and soil-borne diseases (Chadfield et al. 2022). For instances, various allelochemicals released by different crops viz. rice (tricin and momilactone B), sorghum (sorgoleone), sunflower (heliannuols), etc., effectively supress the weeds in crop fields (Khamare et al. 2022). Previous research by Blaise et al. (2020) reported that sun hemp as an intercrop suppressed 43% weed biomass through the release of allelochemicals like phenolics and terpenoids. Various allelopathic actions of intercrops against weeds reported in numerous studies worldwide are summarized in Table 5. Additionally, the root exudates of intercrops play a crucial role in preventing the germination of spores, inhibiting the growth of pathogen mycelium, and impeding the hatching of young nematodes. Verticillium dahliae (Fu et al. 2015) and Cylindrocladium parasiticum (Gao et al. 2014) are good examples to illustrate the mechanism and effectiveness of the allelopathic process. Intercrops from the asteraceae family are known to produce exudates (thiaphenes and thiarubrines) that inhibit the hatching of plant-parasitic nematodes (Zhu and Morel 2019). Similarly, Solanum sisymbriifolium, when grown as an intercrop, protects the primary crop from the potato cyst nematode (Globodera sp.), by producing compounds that prevent nematode eggs from hatching (Mhatre et al. 2021). A recent study by Jiaxing et al. (2021) reported that when wheat was grown in close proximity to faba beans, Fusarium oxysporum f. sp. fabae infections were dramatically reduced through wheat exudates containing tartaric and malic acids.

Table 5 Weed suppression by some intercrops through allelopathic actions

Biocontrol agents/biostimulants

Certain microbes, such as Bacillus, Pseudomonas, Acinetobacter calcoaceticus, Azotobacter, Azospirillum, Mesorhizobium, Bradyrhizobium, and Burkholderia species, serve as biostimulants by producing indole-acetic acid, facilitating nitrogen fixation, producing siderophore, dhurin, and degrading organic matter to enhance plant growth and combat diseases (Ansari et al. 2023). Few instances of microbial consortium to manage plant diseases in organic farming are shown in Fig. 2. Antagonistic microorganisms inhibit pathogens through various mechanisms, including antibiosis, siderophore production to compete for iron, colonization of sites, nutrient acquisition from seeds and roots, activation of plant resistance mechanisms, inactivation of pathogen germination factors found in seed or root exudates, and degradation of pathogenicity factors (Saeed et al. 2021). One effective method by which biocontrol agents (BCA) suppress diseases is through production of antibiotics (Lahlali et al. 2022). Iron plays a crucial role in numerous metabolic and cellular processes in most microbes, with Fe (II) typically being oxidized to Fe (III) in microbial habitats, forming stable complexes. Some organisms secrete siderophores having a strong propensity to sequester iron from the surrounding environment, when the concentration of iron is too low (10^–6 M) to support the microbial growth. Several indicators suggest that siderophore production under iron-limiting conditions may be the reason for the antagonistic behaviour of certain strains of Pseudomonas aeruginosa and Pseudomonas fluorescens towards Fusarium oxysporum and Rhizoctonia solani which are known to cause damping off in various crops (Abo-Zaid et al. 2023). Currently, only a few genera, species, and strains of BCAs are registered for use against soil-borne pathogens such as Coniothyrium minitans, Gliocladium catenulatum, Pseudomonas chlororaphis, Streptomyces griseovirides, Streptomyces lydicus, Trichoderma asperellum, T. atroviride, and T. harzianum. Purpureocillium lilacinum has shown effectiveness against nematodes (Pertot et al. 2015). The impacts of plant growth promoting bacteria (PGPB) on disease and nematode management are listed in Table 6. Additionally, bioagents have been successful in suppressing pests in agricultural fields. Some bioagents for crop insect pest management in organic farming are mentioned in Fig. 3. Two strategies to boost the efficacy of natural enemies include altering the ecosystem to favour them over pests and lessening the detrimental effects of pesticides on natural enemies (Pandey et al. 2022).

Fig. 2

Some microbial consortium used to manage plant diseases in organic farming (Jain et al. 2013)

Table 6 Impact of plant growth promoting bacteria (PGPB) on disease and nematode management under organic farming

Fig. 3

Some bioagents for crop insect pest management in organic farming (Ghosh et al. 2021)

Benefits and constraints of organic farming practices to mitigate biotic stresses

Organic farming methods offer several advantages for managing biotic stresses in agriculture. These strategies are specifically designed to minimize the use of synthetic pesticides which can pose significant environmental hazards. Instead, organic farming focuses on implementing more environmentally friendly and sustainable practices to control diseases, weeds, and pests. The benefits of utilizing organic agricultural methods to mitigate biotic stresses include:

• 1. By eschewing artificial pesticides and herbicides, organic farming helps to reduce the presence of chemical residues in crops. This, in turn, ensures that consumers receive safer and healthier food items. Few non-chemical ways to combat crop disease issues in organic farming are shown in Fig. 4.

• 2. Organic farming emphasizes soil health improvement through the uses of organic matter, cover crops, and minimal soil disturbance. Healthy soil supports a diverse array of beneficial bacteria and organisms that can naturally control diseases and pests.

• 3. By eliminating synthetic pesticides, organic farming methods can aid in preventing or delaying the emergence of pests that have developed resistance to these pesticides.

• 4. Biodiversity thrives on organic farms, with an abundance of beneficial insects and other creatures that can assist in controlling pest populations.

• 5. Organic farming is dedicated to establishing resilient agricultural systems that uphold soil fertility and foster a healthy ecosystem, thereby reducing long-term reliance on chemical inputs.

• 6. By abstaining from synthetic pesticides, organic farming contributes to the safety and health of farm workers through limiting their exposure to potentially harmful substances.

• 7. Organic farming methods have a lower environmental impact, with less harm to unintended organisms, less contamination of soil and water, and a smaller carbon footprint.

Fig. 4

Some instances of crop disease management in organic farming (Ghosh et al. 2021)

Organic farming offers numerous benefits that extend beyond pest management, contributing to the development of environmentally sustainable and enduring agricultural systems. However, it also has certain constraints when it comes to managing biotic stresses. Some of these constraints include:

• 1. Organic farmers often rely on non-chemical techniques to control pests, which may not be as efficient as synthetic insecticides.

• 2. Organic pest control methods can be time-consuming to implement and their efficacy may be influenced by environmental factors. Delayed responses to pest outbreaks may result in significant crop damage.

• 3. Organic crop varieties may have lower resistance to certain diseases, making them more vulnerable to infections. Conventional breeding programmes utilizing synthetic chemicals often produce disease-resistant crop varieties.

• 4. Due to restrictions on synthetic herbicides, organic farmers must utilize mechanical and cultural approaches to control weeds. These approaches may require significant labour and may not always be effective, allowing weeds to compete with crops.

• 5. Effective organic management of weeds, pests, and diseases necessitates a thorough understanding of ecological principles and organic farming practices.

• 6. Synthetic chemical-using conventional farms next to organic farms pose a risk to organic crops. Contamination from pesticide residues may jeopardize the certification of organic crops.

• 7. Weather patterns, such as increased humidity and temperature fluctuations, can exacerbate pest and disease pressures in organic systems. Organic practices may be less resilient in extreme weather conditions.

Conclusions

In modern agriculture, extreme weather conditions can result in outbreaks of biotic stresses. In such situations, adopting eco-friendly organic farming approaches can be a beneficial solution to combat these stresses without contributing to global warming. Despite few limitations, organic farming methods are designed to offer sustainable management of biotic stresses through innovative research and modifications. Given the challenges posed by climate change, it is imperative to develop weather-based forecasting models for significant insect pests and crop diseases; monitor key agricultural pests and diseases as well as non-insect pests; develop resistance to significant insect pests and crop diseases; explore the use of plants, microorganisms, and bioagents for their insecticidal activity against crop pests; create biotic stress management plans for important crops in organic farming situations; estimate economically viable threshold values for the major pests, diseases, and weeds etc. It is important to note that effective stress mitigation technique is not achieved through a single method, but rather through the integration of various eco-friendly organic plant protection techniques. In future, further research is utmost needed to standardize plant protection practices, to increase awareness among farmers regarding usage of the eco-safe farming practices, etc., for achieving the successful plant protection against biotic stresses in organic agriculture.