Bioscience Evidence 2026, Vol.16, No.4, 249-263 http://bioscipublisher.com/index.php/be 255 3.3 Case study 3: ecological engineering in rice fields Ecological engineering in rice fields mainly involves establishing strips of flowering plants along field bunds and field margins. These flowering plants provide nectar, pollen, alternative hosts, and shelter for parasitoids and predators, helping natural enemies suppress pests throughout the growing season. In many rice fields, beneficial insects cannot maintain stable populations because food resources and suitable habitats are limited. Planting nectar-producing flowers along field bunds increases the abundance of predators and parasitoids, reduces pest populations, and maintains rice yield. Field studies showed that ecological engineering significantly increased predator abundance, parasitoid abundance, and parasitism rates compared with both conventionally sprayed fields and untreated fields. At the same time, major pest populations and crop damage were significantly reduced without any yield loss (Ali et al., 2019). Another study involving eight field experiments conducted across different seasons and locations reached similar conclusions. Rice fields with flowering plants consistently supported higher populations of spiders, damselflies, dragonflies, lady beetles, ground beetles, rove beetles, green mirid bugs, and parasitoid wasps. Egg parasitism rates were also higher than those in conventional fields. Average rice yield remained almost the same as that of farmers using routine preventive insecticide applications, with yields of 5.99 t/ha and 5.93 t/ha, respectively (Bari et al., 2025). The value of ecological engineering is not limited to pest control during a single growing season. It also improves the long-term resilience of rice ecosystems. Multi-country and multi-season studies showed that flowering-strip ecological engineering reduced insecticide use by 70%, lowered pest density by 30%, increased biological control by 45%, improved rice yield by 5%, and increased farm profits by 7.5%. In China, plants growing along rice field bunds provide shelter, nectar, alternate hosts, and pollen (SNAP) for parasitoids, cricket-like egg predators, spiders, and other beneficial organisms. When these habitat improvements are combined with avoiding insecticide applications during the early crop stage, biological control becomes even more effective (Heong et al., 2021). Planting sesame, sunflower, soybean, and marigold along field bunds significantly reduced brown planthopper populations, delayed pest outbreaks, increased the activity of spiders, mirid bugs, and rove beetles, and finally improved rice yield. 4 Effects on Pest Population Dynamics 4.1 Lower early-season pest colonization Planting flowering plants along rice field bunds, maintaining functional vegetation, avoiding unnecessary insecticide applications during the early crop stage, and using trap plants can provide food, shelter, and alternative hosts for predators and parasitoids before pest populations become established. Many important rice pests migrate into rice fields from surrounding areas rather than overwintering locally. Therefore, the strength of local ecosystem services largely determines whether invading pests can survive and build their populations. When biodiversity and natural biological control are well maintained, invading pests often remain at low population levels instead of developing into major outbreaks. Lower pest colonization during the early season is closely related to a better balance between pests and natural enemies. During the early growth stage, generalist predators such as spiders and mirid bugs are already abundant in rice fields. These predators gain an early advantage by feeding on alternative prey supported by the detritus food web before major herbivorous pests arrive. Applying organic matter before planting further increases decomposer organisms and predator populations. In contrast, experiments that removed natural enemies during the early season resulted in serious pest outbreaks later in the growing season. These findings show that conserving natural enemies early in the season is a key mechanism for preventing later pest population growth rather than simply being a secondary ecological effect (Settle et al., 1996). Studies also found that plant diversity along rice field bunds is positively associated with predator abundance. In ecological engineering fields, predator numbers increased significantly during the flowering period, while densities of planthoppers and leafhoppers during the early tillering stage remained similar to or lower than those in conventional fields, indicating that natural biological control had already begun to function (Qian et al., 2021).
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