SUSTAINABLE PLANT PEST MANAGEMENT THROUGH OPTIMIZATION AND MINIMIZATION

Abstract

Plant pests and diseases have significant negative impacts on global food security, world trade and rural livelihoods. Climate change exacerbates these impacts in certain parts of the world. Overreliance on pesticides as the primary tool for plant pest management leads to problems such as pesticide resistance and pest resurgence. Environmental and food safety concerns are also associated with overuse of pesticides in crop production. There is clearly a need for a shift in pest management strategies and practices globally. Optimization of structures and functions in crop production agroecosystems through soil conservation practices and cropping diversification can improve pest regulation services provided in the systems. Prioritization of safer alternatives and practices in the IPM pyramid, such as resistant varieties and biopesticides, helps minimize the use of potentially risky agricultural inputs such as synthetic pesticides. Investment is needed to boost the development of innovative green technologies and practices. Production, distribution, use and regulatory capacities need to be strengthened to facilitate large-scale adoption of green technologies and practices. Finally, policy, financial and market instruments should be wielded to provide an enabling environment for the transformation to sustainable plant pest and disease management strategies and practices worldwide.

Graphical abstract

1 GLOBAL STATUS OF PLANT PESTS

There are about 10,000 species of plant pests and diseases that significantly affect crop yield and threaten food security. Yield loss due to pest and disease epidemics are estimated to be between 30% and 40% annually, costing the global economy about 290 billion USD^[1].

Plant pests and diseases cause enormous impacts not only on plant production but also on the livelihoods of people. In 2004, the desert locust (Schistocerca gregaria) swarms destroyed over 80% of crops in Burkina Faso, the Republic of Mali, and the Islamic Republic of Mauritania, endangering livelihoods of a rural population of over eight million^[2]. Since 2016, fall armyworm (Spodoptera frugiperda) has been spreading beyond its native American boundaries, and is now present in over 70 countries in Africa, the Near East, Asia, and the Pacific, resulting in annual yield losses in Africa alone of 11% to 26% (about 9.4 billion USD)^[3].

The most infamous example of the high impact disease epidemics is the potato late blight (Phytophthora infestans) which triggered famine and large-scale human migration in the mid-nineteenth century in Ireland. Since the 1990s, Banana Fusarium wilt caused by Fusarium oxysporum f. sp. cubense tropical race 4 has occurred in Africa, Near East, and Asia, and recently in South America. A recent projection concluded that 17% of current banana growing area with an annual production of 36 Mt worth about 10 billion USD at current prices could be lost over the next 20 years due to this devastating disease^[4]. Since 2013, olive quick decline syndrome caused by the bacterium, Xylella fastidiosa, has spread to more than 715 kha and, by 2017, had severely damaged 6.5 million olive trees in southern Italy, which led to an economic loss of over 1.5 billion USD^[5].

2 GLOBAL CHALLENGES IN PLANT PEST MANAGEMENT

Plant pest management has a key role in ensuring food security and nutrition, promoting food quality and safety, protecting the environment and biodiversity, and facilitating safe trade and economic growth. During the recent desert locust upsurge in the greater Horn of Africa and Yemen, about 2.2 Mha were treated with pesticides between March 2020 and July 2021, resulting in a saving 4.3 Mt of cereals which is enough to feed 28.8 million people and saved 1.3 billion USD of income, in addition to saving the livelihood of two million households of pastoralists^[6]. Calculations show that despite their seemingly high costs, successful pest control programs have a cost-benefit ratio varying between 18:1 and 29:1^[7]. However, we are, currently, facing serious challenges in sustainable plant pest management.

Climate change. The global expansion of pest and disease geographic distribution has been greatly facilitated by climate change^[8] through an increase in pest population sizes and metabolic rates^[9] as well as the number of generations per season^[10]. This has resulted in increased risks of new pest and disease introductions across geographic borders and higher annual production loss worldwide. Crop losses from pests due to climate change vary by latitude and are higher in temperate regions due to larger increases in both insect population sizes and metabolic rates than in the tropics^[11]. A recent high-level review by the International Plant Protection Convention Secretariat^[12] calls for international cooperation and development of harmonized plant protection strategies to help countries successfully adapt their pest risk management measures to climate change.

Environmental pollution and associated problems. Sánchez-Bayo et al.^[13] estimated that 64% of global agricultural land is at risk of pesticide pollution by more than one active ingredient, posing serious risks for soil and water biodiversity connected with the land. The overwhelming majority of global biodiversity is insects with up to 1% of the one million described species being pests. Environmental pollution by agricultural chemicals, such as pesticides and fertilizers, are one of the major drivers for the decline of insect fauna worldwide, including pollinators, natural enemies and decomposers^[14]. Agricultural pesticide is similarly associated with the decline of other non-target species, such as farmland and grassland birds^[换为,16]. Use of certain compounds such as metals and antibiotics in crop production have also contributed to the rise of antimicrobial resistance worldwide^[16].

Three R problems. As the primary tool for pest management, the global use of pesticides has risen to over 4 Mt·yr^−1[17], forcing us to recall the perils highlighted in Rachel Carson’s book, Silent Spring^[18]. Inappropriate use of pesticides has caused severe negative impacts on sustainable pest management through pesticide resistance, pesticide residues, and pest resurgence (the three R problems).

Since 1910, there was a steady increase in documented insecticide resistance in pests with 7747 accumulative cases by 2010^[19] and over 10,000 accumulative cases by 2020^[20]. A similar increase has been reported for the number of arthropod species with resistance against at least one insecticidal compound with 553 species reported by 2010^[19]. As climate change is predicted to increase the number of arthropod generations per season, this increased voltinism will contribute to pesticide resistance problems in the future.

Contamination of pesticide residue was ranked as one of the top food safety concerns in fresh-food chain together with bacterial pathogens, foodborne viruses and mycotoxins^[21]. Indeed, consumption of fresh agricultural produce may form the main route for chronic exposure to pesticides^[22]. Pesticide residues in an agricultural commodity may also form a significant trade barrier.

Pest resurgence is another phenomenon associated with the overuse of pesticide. There are two types of pest resurgence, primary and secondary. Primary pest resurgence occurs when “the target arthropod pest population responds to insecticide or acaricide treatment by increasing to a level at least as high or higher than in an untreated control or higher than the level observed before the treatment”^[23], such as planthoppers in rice^[24], and two-spotted spider mite in various horticultural crops^[换为,26]. Secondary pest resurgence occurs when a “non-target and injurious pest populations increases in a crop after it is treated with a pesticide to control a primary pest population”^[23], such as apple leafhopper in apple^[27]. Destruction of natural enemy populations, reduction of competition by other herbivorous arthropods, hormesis and alteration of host plant quality have been documented as possible mechanisms for primary and secondary pest resurgence^[换为,28].

3 NEED FOR A CHANGE OF PLANT PEST MANAGEMENT STRATEGIES

Plant pest management directly and indirectly contributes to achieving the Sustainable Development Goals (SDGs) of the United Nations 2030 Agenda, in particularly food security and nutrition (SDG 2), environment and biodiversity protection (SDG 13 and SDG 15), and safe trade and economic growth (SDG 8 and SDG 17). To fulfill this crucial mission while coping with the increased challenges, a sustainable plant pest management approach should be adopted with two main strategies, optimization and minimization.

Optimization of structures, functions and services of crop production agroecosystems. Like other types of ecosystems, agroecosystems have their inherent structures and functions. There is a plethora of agroecosystem structures and functions across the globe, ranging from large-scale annual crop monocultures to arid-land pastoral systems and species-rich home gardens. Each of these agroecosystems delivers various levels of services that benefit human welfare, such as food, feed and fiber provision, biodiversity conservation, pest control, and carbon sequestration, as well as disservices, such as loss of wildlife habitat, pesticide poisoning and greenhouse gas emission. Both farm and landscape-level management practices affect the structure and function of a given agroecosystem and eventually determine the level of services and disservices associated with the system^[29].

As natural pest regulation is one of the ecosystem services inherent in all agroecosystems, farm and landscape-level practices that optimize this service should be identified to have positive impacts on crop yield, farm income and natural enemies, but negative impacts on plant pests and diseases. Practices such as crop rotation or vegetative diversification of field periphery have been shown to conserve and increase the functionality of natural enemies and thus improve natural pest regulations in various cropping systems^[换为,30]. Soil conservation practices, such as mulching, no-till and organic amendment, have also been shown to limit pest populations by generally improving plant vigor and conserving natural enemies^[31]. The effect of these practices varies with agroecosystems, therefore careful studies are needed to tailor the practices that optimize the ecosystem services in a given agroecosystem^[32].

Minimization of crop damage, biodiversity loss and pesticide risk. Minimization of these three key components can be effectively achieved only by adopting an integrated pest management (IPM) as the operational framework of sustainable plant protection into the future (Fig. 1). This IPM framework carefully considers all available pest control techniques before subsequently integrating appropriate measures that discourage the development of pest populations. It combines biological, chemical, physical and crop-specific (cultural) management practices to grow healthy crops and minimize the use of pesticides, thus reducing risks posed by pesticides to human health and the environment.

The IPM framework prioritizes prevention strategies as well as the use of resistant cultivars, cultural control and landscape management before moving on to the use of biopesticides and, as the very last resort, synthetic pesticides. Among those, priority should be given to lower-toxicity options, such as, for example, insect growth regulators. Also, biopesticides can be effective when pests evolve resistance to older, widely-used synthetic pesticides^[34]. Careful monitoring, field scouting and the application of scientifically derived economic thresholds must guide the use of pesticides. Additionally, and more importantly, the application of pesticides must take into account environmental and human health considerations.

4 GREEN INNOVATION FOR SUSTAINABLE PLANT PEST MANAGEMENT

Sustainable agriculture calls for sustainable plant pest management, which can be effectively achieved through the green plant protection. The green innovation is the basis for green plant protection through optimization and minimization. The underlying principle for green plant protection is to be less dependent on synthetic pesticides and fertilizers but use more the innate ability of crop plants to resist pests, harsh climates and high salinity. A healthy soil-water-plant ecology should be prompted to improve both productivity and harmony between agriculture and the increasing world population^[34]. Thus, management of plant pests should undergo a paradigm shift from reliance on synthetic pesticides to a sustainable and preventive strategy based on optimization and minimization. Such a shift can be ensured only through the following:

(1) Innovation for green technologies

- Establishing green agricultural product-based cropping systems, such as green production system for major agricultural crops (e.g., maize, potato and rice), and special agricultural crops (e.g., fiber, fruit and vegetables).

- Developing green technical-based pest control systems, such as green technical system for control of brown plant hoppers in rice, fall armyworm in maize, and Colorado potato beetle in potato.

- Setting up green agricultural input-based pest control systems, such as Trichogramma control of corn borer throughout the corn-growing season, sex pheromone control of cabbage caterpillars throughout the cabbage-growing season and light trapping control of stem borer throughout the rice-growing season.

- Promoting adoption and implementation of most advanced technologies for green plant protection, such as modern biotechnology and new material technology, for example, RNA-based active ingredients aim to achieve selectivity and sustainability in future crop protection agents^[35], nanotechnology ensures targeted pesticide release^[36], and the use of drones to facilitate locust monitoring and control^[37].

(2) Green innovation for dissemination and capacity strengthening

- Strengthening farmer field schools as a participatory approach to improve farmer capacity to understand agroecosystems dynamics and to attract and maintain natural enemies on their farms and produce their own biopesticides and botanicals^[38].

- Establishing green-technology transformation platform through digital extension to organize a series of activities for integration, demonstration, validation and dissemination of green protection technologies to the field, and also showcase green protection technologies through extension conferences, field days and exhibitions^[39].

- Adopting modern information and digital technology to enhance dissemination and extension of green protection technologies, for example, remote sensing combined with precision agriculture facilitate detection and management of crop diseases^[40];

- Exploring transformation mechanism to promote green plant protection, such as farmers plus farmer association, and farmers plus farmer association plus multi-stakeholders (agricultural research and education and agribusiness)^[41].

(3) Green innovation for institutional interventions

- Strengthening relevant policies through improving pesticide regulatory systems^[42], in particular to facilitate biocontrol registration and quality control^[43].

- Improving commercial availability of biopesticides at low cost by developing local biocontrol industry (financial and technical capacity)^[44].

- Scaling up sustainable pesticide management through voluntary sustainability standards to offer more remunerative prices or beneficial market conditions, reward the exclusion of the most hazardous pesticides and help share the risk (or perceived risk) of adoption with consumers^[45].

- Providing access to financial instruments (e.g., loans/credits, direct subsidies to farmers, and insurance) to help farmers overcome the first hurdles to adopt green protection technologies (e.g., UNCTAD^[46]).

- Promoting institutional, national, regional international cooperation by establishing relevant mechanisms for information sharing, data collection, early warning, capacity building and development of strategic/contingency plans for sustainable plant protection^[47].

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The Author(s) 2021. Published by Higher Education Press. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0)