Ecological engineering for rice pest suppression in China. A review

Ecological engineering for pest suppression aimed at promoting ecosystem services of biological control, involves a range of environmentally-benign approaches to conserve and promote arthropod natural enemies and suppress pest populations, and thus reduce the need for insecticide use. Major components in rice pest management involve providing vegetation that favors parasitoid overwintering during the fallow seasons, growing nectar-producing flowering plants on the rice bunds to enhance the biocontrol function, and planting trap plants around rice fields to minimize the initial populations of pests. Complementary tactics involve using sex pheromone traps and mass-releasing Trichogramma spp. parasitoids to reduce the densities of Lepidoptera pests, and synergistically culturing ducks or fish to reduce other planthoppers. After a decade of laboratory and field research accompanied by on-farm demonstrations, ecological engineering for rice pest management has shown growth in both the underlying body of theory and practical adoption, especially in China. Ecological engineering approaches have been listed as a China National Recommendation by the Ministry of Agriculture and Rural Affairs of the People’s Republic of China (MARA) since 2014. We feel this is worth documenting, especially because only a portion of that work has been reported in English-language journals so would otherwise remain “invisible” to the international scientific community. This study is the first time to systematically review the research that has allowed this rapid development and uptake in China, highlighting priorities for future research that will enhance the prospects for ecological engineering in this and other agricultural systems internationally.


Introduction
Rice, the most important food crop in the world, is an essential staple food in China with cultivation dating back for more than six thousand years (Yuan 2014). The Green Revolution starting in the 1960s was aimed at meeting the increasing demand for food from rapid human population growth. Rice yields have been significantly increased with the wide-scale adoption of high-yielding varieties, and extensive use of chemical pesticides and fertilizers . However, the overuse of chemical pesticides results in severe threats to the sustainability and safety of agricultural production resulted from widespread insecticide resistance in pest populations a pressing problem (Conway and Pretty 1991;Xu et al. 2017). Even though it has become essential to reduce reliance on chemical pesticides to improve food security by improved pest management in rice. Compared to the overuse of chemical pesticides, conservation biological control (CBC) is a more sustainable practice that is a part of integrated pest management (IPM), and can be an effective means of reversing the negative effects of agricultural intensification. CBC aims to enhance pest control by improving resources for natural enemies and reducing the disadvantages of agricultural intensification for natural enemy populations (Holland et al. 2016;Shields et al. 2019). This can be achieved by a variety of management practices that has matured into an informationrich approach which includes ecological engineering (Gurr et al. 2004). Ecological engineering employs habitat management to promote ecosystem services of biological control by providing food, hosts, and shelter, for natural enemies of pests Westphal et al. 2015;Heong et al. 2021). Using practices to support biological control has been advocated since the 1960s (Pathak 1968;Yasumatsu and Torh 1968). Though largely overshadowed by Green Revolution technologies, China had made use of Integrated Pest Control (IPC, the predecessor of IPM) during the 1960s-1970s-this included cultural practices and biological control (Brader 1979). Since the end of 1970s, researchers in China increasingly realized the importance of trap crops and non-crop habitats in the rice ecosystem, especially the effects of weedy bunds on the natural enemies of rice herbivores (Brader 1979;Qiu et al. 1998;Yu et al. 1996;Zhuang 1989). More generally, research on ecological engineering for pest control in various crop systems has developed markedly over the last 40 years though translation into widespread adoption was limited few crop species Wu et al. 2009;Zhao et al. 2016). The principles of ecological engineering were originally proposed by Shijun Ma in 1979 (Sun and Qi 2017), and the earliest study (for which data are available recorded in English) on ecological engineering for pest management was on cotton aphid control by ladybird beetles (Li and Du 1984). Over the past two decades, research has been conducted in many cropping systems. These laboratory and field studies have produced empirical evidence to support the concept of ecological engineering and refined the techniques of ecological engineering for pest management. Examples in China include wheat (Zhao et al. 2013), cotton Liu et al. 2018), tea Zhang et al. 2016a), soybean (Zhang and Swinton 2012), brassica vegetables , and orchards (Wan et al. 2019a). As a formal program, ecological engineering techniques (EET) for rice pest management were initiated in China in 2008 with the first demonstration farm was established in Zhejiang Province, China (Fig. 1). Ecological engineering for rice pest management is now integrated with both theory and practice into a comprehensive system (Table 1). Ecological engineering techniques for rice pest management include ecological engineering techniques (EET) and supporting techniques for higher efficiency of EET. Ecological engineering techniques improve the ecosystem services of pest control by ecological approaches. In contrast, supporting techniques are those that operate by other mechanisms (releasing natural enemies and applying biopesticides) or that are implemented for wider, production-related issues (coculture). These ecological engineering techniques can enhance the strength of ecosystem services and reduce the need for pesticide use (especially insecticides). This study is the first time to systematically review research on the practical introduction of ecological engineering for rice pest suppression in China with the aim of providing guidance for its implementation and replications in other crops and regions.
2 Ecological engineering techniques (EET) for rice pest management 2.1 Increasing crop system compatibility of pest management Typically, intensified rice-based agricultural production systems are oversimplified farm landscapes where non-crop flora is greatly reduced. In addition, the overuse of fertilizers and pesticides is widespread . These results in a weakening of contributions of ecosystem services by natural enemies of crop pests, which in turn results in frequent pest outbreaks . In recent decades, the acknowledgement of the importance of non-crop flora on farmlands has initiated research on enhancing ecosystem services provided by improved biodiversity in farmland Wan et al. 2018). The practice of habitat manipulation for arthropod pest management is a critical component of ecological engineering for pest suppression aimed at improving the ecosystem services of biological control (Gurr et al. 2004;Gurr et al. 2017).
Habitat management introduces plant-based resources for natural enemies such as shelter, nectar, alternative prey, and pollen ). Increasing crop system compatibility in agroecosystems brings stability to arthropod communities and populations, which will better address pest suppression.

Shelter for natural enemies
Providing arthropod natural enemies with shelter allows them to overwinter near crop fields, prevents communities from being wiped out from insecticide use, and allows rapid recolonization during early crop stages or after disruptions. Pest suppression function has been enhanced in rice by growing green manure crops (the Chinese milk vetch Astragalus sinicus), which give shelter and food for natural enemies to overwinter after the rice season. Other examples of providing shelter include incorporating the rice straw to the field, maintaining graminaceous plants around rice fields, intercropping with Zizania latifolia and neighboring with vegetable crops (Table 1). Providing these forms of shelter for natural enemies has been shown to suppress pest populations so that densities do not reach threshold levels. Therefore, pesticides use can be avoided Huang et al. 2005;Zhang et al. 2011).

Alternative hosts for natural enemies
The banker plant system, as a form of CBC, consists of a noncrop plant which is consciously nourished a non-pest herbivore as an alternative host for natural enemies of the target crop pest (Frank 2010). Banker plants support the temporal continuity of key natural enemy species by providing, during the winter fallow and early in the rice season, prey and hosts that support these beneficial arthropods during periods when the rice herbivores are absent or scarce ). Banker plants thereby prevent the local extinction of natural enemies of rice pests, and build up natural enemy densities. In a banker plant system, the alternative host or prey is ideally a specialist to the banker plant so that it does not pose a risk to the focal or other crops, and the natural enemies need to have the ability to disperse across the crop field and a wide enough host/prey range to attack the focal pest.
Two banker plant systems used in rice production are the Zizania latifolia -Saccharosydne procerus -Anagrus spp. (ZSA) (Fig. 2a) and Leersia sayanuka -Nilaparvata muiri -Anagrus spp. & Typhus chinensis (LNA&T) (Fig. 2b) ( Table 1). Laboratory studies showed that BPH was unable to complete its life cycle on L. sayanuka, and N. muiri could not complete its life cycle on rice. Thus, planting L. sayanuka poses no risk of it serving as an alternative host to the rice pest N. lugens. BPH densities in field studies were found to be significantly lower in rice fields grown with the banker plant compared to control rice fields without the banker plant ). The ZSA system involves the intercropping of rice with the aquatic vegetable Z. latifolia. Green slender planthopper, Saccharosydne procerus, is the main pest of Z. latifolia, but it does not feed on rice, and shares the egg parasitoid Anagrus spp. with rice plant-and leafhoppers and provides Anagrus spp. with food in winter Zheng et al. 1999). If well chosen, plants such as Zizania serve the dual function of proving shelter to a range of natural enemy taxa as well as supporting hosts of more specific parasitoid species.

Floral resources for natural enemies
Floral resources can enhance the effectiveness of natural enemies since they attract them, prolong their longevity, and increase their fecundity (Lu et al. 2014). Accordingly, the inclusion of suitable flowering plants in non-crop habitats can improve the activity and impact of natural enemies. A growing number of studies have demonstrated the abundance and fecundity of natural enemies were increased in the presence of floral resources (Lu et al. 2014;Zhao et al. 2016), particularly in the rice-based ecosystem (Table 1), with measurable benefits in terms of pest densities, rice yield, reduced pesticide use, and overall economic advantage (Gurr et al. 2016). Sesame (Sesamum indicum) has been the most popular flowering plant used in ecological engineering techniques for rice pest management because it serves as a lucrative dual income crop and has been listed as a central component of the nationally recommended sustainable management of rice insect pests by ecological engineering techniques in China (MARA 2014).

Keeping the early rice stages insecticide free
Neutral insects, especially detritivore chironomid midges, whose population could be as many as 4.5 million per hm 2 in a rice field, can be an essential food source for predators early in the rice season (Li et al. 2010;Wu et al. 1994).
Populations of natural enemies and neutral insects are easily reduced by injudicious use of insecticides. This decrease in the biodiversity of arthropods early in the season allows a natural build-up of pests like rice planthoppers and rice leaf folders later in the crop (Way and Heong 1994). Generally, in the first 30 days after transplanting, pest densities are low, and insecticide applications do not impact on crop yield, therefore, are not necessary (Xu et al. 2017;ZQTSB 2017). Many field studies have indicated that applying less than 1-2 insecticide sprays in the early rice stage will not affect the growth and yields of rice Hu et al. 1996).

Cultural methods
The overuse of nitrogen fertilizers in rice is common across Asia and is most acute in China (Cheng 2009;Ding et al. 2018;Wang et al. 2019). The adoption of hybrid rice for high yields resulted in significant increases in the use of nitrogen across Asia (Wang and Peng 2017). Higher levels of nitrogen in rice also increased herbivore feeding, survival rates, and reproduction (Lu et al. 2007). In many areas, outbreaks of pests, including planthoppers, leaf rollers, and stem borers, have been closely linked to excessive use of nitrogen (Hu et al. 2016;Lu et al. 2007;Lu and Heong 2009). High nitrogen use also negatively impact natural enemy performance, which increases the risk of BPH outbreaks (Zhu et al. 2017b). The high-efficiency technology system for nitrogen fertilizer applications in rice fields has been developed . Optimum nitrogen estimated by this system limits the number of ineffective tillers, and improves yield while minimizing disease occurrence and pest damage Zhong et al. 2010). Nitrogen (N), phosphorus (P), and potassium (K) are essential nutrients for rice that must be applied in rice fields to maintain productivity (Rashid et al. 2016), but the unbalanced and excessive use of N, P, and K is common in rice production (Xu et al. 2017). Balanced application of the essential nutrients improves utilization efficiency of nitrogen fertilizer in the rice field, as well as potassium fertilizer, in turn, improves rice plant vigor, and enhances rice resistance to rice leaf folder and other pests (de Kraker et al. 2000). There is also a positive relationship between rice resistance to pests and the application of silicon fertilizer (Liu et al. 2017). Silicon also plays important roles in rice plant defense against abiotic stress (Tripathi et al. 2014), such as lodging (Deng et al. 2011), heat and drought (Agarie et al. 1998). Silicon fertilizer can contribute to pest control by inhibiting feeding and oviposition of pests, as well as enhancing the attraction of parasitoids (Liu et al. 2017) (Table 1).

Minimizing initial pest population using trap plants
The stem borers including RSB, pink rice borer (PRB) Sesamia inferen and yellow rice borer (YRB) Scirpophaga incertulas, lay eggs on vetiver grass Vetiveria zizanioides, but the larvae cannot complete their life cycle feeding on this grass making it a useful "dead-end host" (Chen et al. 2007;Gao et al. 2015;Lu et al. 2017;Zheng et al. 2009). The underlying mechanisms are (1) bioactive substances in vetiver grass are toxic and inhibit RSB larval growth; (2) extracts of vetiver grass disturb the dynamic equilibrium of Superoxide Dismutase (SOD), Catalase (CAT), and Peroxidase (POD), and inhibit the esterase and cytochrome P450 enzyme activities, leading to a loss of the larvae function in detoxification and metabolism; (3) vetiver grass has lower nutritional value than rice; and (4) the V. zizanioides extract inhibits RSBF; the protective efficacies were 66.7% in an outdoor pot-cultivation test (Gao et al. 2011(Gao et al. , 2015Lu et al. 2017). With these characteristics, planting vetiver grass around paddy fields can attract stem borer adults to lay eggs on its leaves and reduce the population in rice fields ). The best planting period is from late March to early April in temperate regions of China (planting 4-8 weeks before rice planting in the spring), and the appropriate planting coverage is 6-10% of the rice field (Chen et al. 2007). The optimal planting pattern is in clusters with spacing of 3-5 m and line spacing of 50-60 m ). The aim of planting this trap crop is to keep the density of the stem borers in the rice to below the thresholds in order to avoid using pesticides.

Inundative releasing Trichogramma wasps
Trichogramma species have been studied extensively and play a vital role in insect pest management in China (Lou et al. 2013). Research into releasing Trichogramma spp. for the control of main Lepidoptera pests in rice fields has been conducted since the 1950s in China (Table S1). Constraints on the use of Trichogramma spp. include appropriate species selection, population rejuvenation, and field application techniques (Babendreier et al. 2019). In recent years, applications of Trichogramma have gained renewed interest (Xu et al. 2017;Babendreier et al. 2019). Technologies for releasing Trichogramma into rice fields have advanced in recent years incorporating unmanned aerial vehicles "drones" for rapid dispersal and release (Xu et al. 2017) as well as nectar food supplements to maximise post-release longevity. Research into species selection, the interval of release timing and density and release heights could contribute to further improvements in the large-scale use of Trichogramma spp. in rice (Xu et al. 2017).

Agroecological intensification by co-culture systems
Rice co-culture systems incorporating, such as rice-duck, ricefish, rice-soft shelled turtle, rice-crab, or all combinations, can provide benefits compared to traditional rice monocultures, especially due to the animal component of the system consuming pest species Xu et al. 2017) ( Table 1). The rice-fish co-culture model has a long history in China (Huang et al. 2014). Recent studies show the rice-fish co-culture can decrease herbivore insect abundance, reduce weed abundance, richness of species and biomass, increase invertebrate predator abundance, reduce pesticide use, and enhance both soil and grain quality in terms of increasing available nitrogen, phosphorus, potassium, total nitrogen, and organic matter content of the soil environment in ricefish production systems, as well as increasing head rice rate, milled rice rate, and protein content of grain quality in rice-fish production systems (Li et al. 2022;Wan et al. 2019b;Xie et al. 2011). Rice-fish co-culture has been demonstrated to provide a more than 10% higher net income than rice monoculture (Wan et al. 2019b). The rice-duck co-culture model is but widespread and sporadic in China but has been widely promoted during the last two decades. It can reduce fertilizer use by over 30% and pesticide use by 50%, and significantly improve rice quality in terms of no herbicide and less pesticide used, and increasing coarse rice rate, head rice rate, gel consistency, and chalkiness rate of grain quality in rice-duck production systems, compared with the conventional farming model (Huang et al. 2014). The ongoing exploration of coculture models means new co-culture models in the rice ecosystem regularly appear, like rice-crab (Guo et al. 2015), ricecrayfish (Jiang and Cao 2021), rice-soft shelled turtle (Zhang et al. 2016b), and rice-frog (Fang et al. 2021) (Fig. 3).

Minimizing initial pest population using sex pheromones
Some pest control strategies involve changing pest behavior through chemicals, visual, or audio signals (Rodriguez-Saona and Stelinski 2009). Like other IPM techniques, the use of methods to manipulate insect behavior previously was not given much attention due to the low cost and convenience of using insecticides.
In many insect species, especially lepidopteran pests, the females emit the sex pheromone to attract the males (Rodriguez-Saona and Stelinski 2009). In rice fields, sex pheromones for controlling the rice stem borer (RSB) Chilo suppressalis and rice leaf folder (RLF) Cnaphalocrocis medinalis have been developed (Xu et al. 2017). The use of dry traps which have low maintenance needs during the rice season has advantages over conventional traps which need regular replacement of water or lures (Si et al. 2016;Zhu et al. 2013). The results of field applications of sex pheromone traps show that the control effects were more than 50% better when combined with other pest management strategies at a large scale rather than when used as a sole means of pest suppression. Use of sex pheromone traps combined with other pest control strategies against RSB and RLF can reduce insecticide spraying to just one to two times a season, with a cost comparable to that of using chemical pesticides (Du et al. 2013;Si et al. 2016).

Biopesticides
Biopesticides are increasingly popular in China as they meet the increasing consumer demand for food-safety. Bacillus thuringiensis (Bt) is the most popular biopesticide and is officially recommended to control rice stem borers and rice leaf folder in China (Xu et al. 2017). Mamestra brassicae nuclear polyhedrosis virus (MbNPV), Beauveria bassiana, and Empedobacter brevis show high insecticidal activities on rice Lepidoptera insect pests Xu et al. 2017;Zheng et al. 2016) (Table 1). Cnaphalocrocis medinalis granulovirus (CnmeGV) is also another potentially effective biopesticide to control RLF (Liu et al. 2013;Zhang et al. 2014). The ideal biopesticide application methods in rice involve the following: using Bt and Bacillus subtilis before the transplanting of rice seedlings to prevent and reduce the occurrence of field diseases and pests; using Bt to control rice Lepidoptera insect pests and use of the fungus Beauveria bassiana to control rice planthoppers during the ricegrowing season when necessary.

Case study of ecological engineering for rice pest suppression
The Zhejiang Academy of Agricultural Sciences (ZAAS) and the Jinhua Plant Protection Station (JPPS) in collaboration with the International Rice Research Institute (IRRI) and Charles Sturt University (CSU) initiated a pioneering attempt to manage rice insect pests by developing a program for ecological engineering for rice pest suppression in 2008. The experimental site was located at Si Ping village, Jinhua city, Zhejiang province, set in an area with nearby mountains and high-quality water resources. Although the original ecosystem had not been greatly disturbed, the areas used for rice production had been impacted by intensive cultivation and the overuse of chemical fertilizers and pesticides. The main techniques included manipulation of vegetation to promote natural enemies, specifically, planting nectar-rich plants like sesame (Sesamum indicum), zero insecticide sprays during the first 30 days after transplanting and reducing over 20% of nitrogen fertilizer than conventional application. The goal was to reduce the use of chemical pesticide by 60-80%, to keep yield losses by major pests to less than 3%, and to gradually recover the natural pest control function of the ecosystem. The field studies were done on a farm scale at Si Ping village since 2008. After that, similar field studies were tested at several farms during 2009 to 2018 in Zhejiang province, such as Ningbo, Xiaoshan, Lishui, Wenling, and Wenzhou. The scale of each study site was over 10 ha.

Improved biological control
Field surveys showed that the numbers of Anagrus spp. and invertebrate predators, including damselflies (e.g., Ischnura sengalensis, Agriocnemis femina) in the ecological engineering fields, were over four times higher than those in the farmer's fields with conventional agricultural operations .
The population density of the dominant frog species, Fejervarya multistriata, in ecological engineering for rice pest suppression fields was over three times than those in the farmer's fields (Kong et al. 2016). The number of RPH egg parasitoids near the ridge was doubled than those in the farmer's fields in the tiller stage and the filling stage of rice, but the population of RPH was reduced over five times by implementing ecological engineering for rice pest management than those in the farmer's fields in the tiller stage and the filling stage of rice . A 5-year follow-up survey showed that the numbers of functional guilds of predatory Odonata and Tetragnathidae, as well as the larval parasitoids of RLF in ecological engineering for rice pest suppression fields, were significantly higher (1.63-8.94 times, 0-3.69 times, 1.20-2.47 times, respectively) than those in the control fields (Zhu et al. 2017c). Furthermore, the ecological engineering strategy promoted the breeding of aquatic predators and neutral insects in rice fields, because of the technique of keeping the early rice stages insecticide free could increase the biodiversity and the population density of aquatic predators and neutral insects, as well as the techniques of growing green manure crops after rice season, maintaining graminaceous plants around rice fields and intercropping Zizania latifolia could provide a stable habitat with plant-based resources for such as shelter, nectar, alternative prey, and pollen ).

Reduced insecticide applications
Applying ecological engineering for rice pest suppression dramatically reduced chemical insecticide applications. Chemical insecticides were not used at all in 2009 and 2011 against rice planthoppers, and the overall number of insecticides was reduced by more than 75% in ecological engineering for rice pest suppression fields compared to the control fields in Jinhua, Zhejiang ).

Increased economic benefits
With the application of ecological engineering, pest populations were lower throughout the rice-growing season, and compared with the control fields no yield loss was found (Gurr et al. 2016). Insecticide use was reduced by 75%, with cost savings for insecticides and labor amounting to over US $400 per hectare per year . With the concerted efforts of the research team and agricultural extension services, ecological engineering for rice pest suppression has been further recognized in society. Rice from EET fields could fetch a price over five times higher than the normal market price, as the benefits of reduced pesticides use are highly valued by the public with the improvement of living standard . Similar positive results were also observed in other sites in Zhejiang province with the same design as Jinhua, such as Xiaoshan, Lishui, Wenling, and Wenzhou.

EET trade-offs
Certainly, ecological engineering techniques for rice pest suppression improve the ecosystem services of rice pest control. The trade-offs of EET are also worthy of note, even though no independent evidence has been reports to date. But there are anecdotal reports that snake densities are enhanced in some sites where ecological engineering is implemented (possibly reflecting increased frog densities as a result of lower insecticide use). Farmers from EET rice area also give the feedback that the population of egret is much high in the rice field where ecological engineering is implemented, especially early in the rice planting season (possibly reflecting increased small animal densities, such as frogs, earthworm, and minnows). In addition, effects of weedy rice bunds on rat population also should be considered. The systematic review of all underlying risks is necessary for the future work.

The current situation of ecological engineering for rice pest suppression in China
Ecological engineering for rice pest suppression was standardized by Jinhua city local standard in 2014 (JQTSB 2014) and by Zhejiang province local standard in 2017 (ZQTSB 2017), promoting the popularization of ecological engineering for rice pest suppression in Zhejiang province. Over 80,000 ha of rice fields, which accounts for about 10% of the rice planting area of Zhejiang province, employed the whole-process technical scheme of ecological engineering for rice pest suppression in 2018. The measures included (1) maintaining functional graminaceous weeds around rice fields to provide native arthropod natural enemies with shelter and alternative hosts in winter, and during pesticide applications; (2) intercropping zizania (Zizania latifolia) in rice fields as a shelter for spiders, frogs, and Anagrus parasitoids of leaf-and planthoppers; (3) inter-planting nectar crops such as sesame on field bunds to enhance biological control functioning of Trichogramma and Anagrus parasitoids and the predator Cyrtorhinus lividipennis; (4) planting vetiver grass (Vetiveria zizanioides) as a trap plant to attract rice stem borers to lay eggs; (5) inundative releases of Trichogramma spp. When necessary to enhance biological control of lepidopteran pests of rice.
Insecticide use has been reduced by 50% across the scheme of ecological engineering for rice pest suppression. Ecological engineering for rice pest suppression also has been promoted energetically by the General Station of Plant Protection and Quarantine of Zhejiang Province and the local Plant Protection Station in Zhejiang as the main technology for green methodologies for the prevention and control of rice pests by various ways (Fig. 4). Over 900 demonstration sites had been established by 2018, which extended over 538,000 ha of rice fields (data from the General Station of Plant Protection and Quarantine of Zhejiang Province, count by rice fields which adopted more than one ecological engineering measure). Now, in a national recommended technology by the Ministry of Agriculture and Rural Affairs of the People's Republic of China (MARA 2014), ecological engineering for rice pest suppression has been extended to over 3,000,000 ha of rice fields in southern China, such as Jiangxi province, Jiangsu province, Hunan province, Hubei province, Anhui province, Shanghai, Guizhou province, Yunnan province, and Guangxi province since 2014 (Fu et al. 2021).

Conclusions and perspectives
New research directions for pest suppression based on ecological engineering techniques have been explored in recent decades and especially this century (Gurr et al. 2004;Heong et al. 2021). The benefits of these techniques extend over multiple trophic levels, promoting natural enemies, suppressing pests, and enhancing crop productivity. In some cases, studies have shown more comprehensive benefits, including reduced insecticide use and financial advantage. Reflecting this, the new concept of "green plant protection" has been widely accepted in China (Lu et al. 2012). It emphasizes the support and safeguards needed to obtain high-yield, good quality, and ecologically sustainable agricultural systems. Ecological engineering for rice pest suppression has been recommended as one of the key strategies for the sustainable management of rice pests by the National Agriculture Technology Extension and Service Centre since 2013, and has been listed as a national recommended technology by the Ministry of Agriculture and Rural Affairs of China since 2014 (MARA 2014). Only a portion of that work has been reported in English-language journals so would otherwise remain "invisible" to the international scientific community, hence the need to document the work in the current form in order to allow for its expansion to worldwide rice production areas.
Although ecological engineering has gained increasing acceptance among biological control experts and agriculture practitioners Settele et al. 2019), there are still important knowledge gaps, including the wider use of floral resources. A growing number of studies have demonstrated the abundance and fecundity of natural enemies increased in the presence of a range of floral resources (Lu et al. 2014;Zhu et al. 2018). Foremost is the fact that all work has been dependent upon the empirical testing of multiple candidate plants to identify suitable species for each pest-nature enemy interaction in each agroecosystem. It is labor-and timeconsuming, and sometimes, decisions are made on a weak evidence base. Ecological engineering for rice pest suppression still needs a scientific evaluation system so that it can be promoted and applied in a broader range of agroecosystems.
Ecologically based pest management in agroecosystems has become increasingly important worldwide (Pretty 2018; Reddy 2017; Zhao et al. 2016). Ecological engineering for rice pest suppression also has been explored in other Asian rice production systems (Ginigaddara 2018), such as the Philippines (Horgan 2017), Indonesia (Sparta et al. 2021), Vietnam (Horgan et al. 2022;Settele et al. 2019), Bangladesh (Ali et al. 2019), and India (Chandrasekar et al. 2017). The present account of ecological engineering for rice pest suppression in China provides a framework for its expansion to other areas and for adaptation for use in a wider range of crop systems.
Authors' contributions ZL and GMG led the planning and refinement of the manuscript. PZ wrote the manuscript. All authors contributed critically to the drafts and gave final approval for publication.

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Conflict of interest The authors declare no competing interests.
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