Bioscience Evidence 2026, Vol.16, No.4, 249-263 http://bioscipublisher.com/index.php/be 256 4.2 Slower population growth during the mid-season From the tillering stage through stem elongation and panicle initiation, eco-friendly pest management mainly slows the rate of pest population growth rather than causing immediate pest elimination. Planting nectar-producing flowering plants along field bunds increases the abundance of predators and parasitoids as well as parasitism rates. At the same time, both pest populations and crop damage decrease, indicating that biological control continues to suppress pest development throughout the growing season. Ecological engineering fields consistently support larger populations of spiders, damselflies, dragonflies, lady beetles, ground beetles, rove beetles, green mirid bugs, and parasitoid wasps than conventionally managed rice fields. Egg parasitism rates of brown planthoppers, yellow stem borers, rice leaffolders, and rice thrips are also higher. This advantage allows pest populations to remain below the economic threshold. The suppressive effect is particularly clear for brown planthoppers and rice leaffolders, which are two of the most important pests during the middle of the growing season. Field experiments in India showed that ecological engineering reduced brown planthopper densities to 6.3 and 9.4 insects per hill in 2019 and 2020, respectively, compared with 9.8 and 14.4 insects per hill in the control treatment. Pest outbreaks also occurred later and reached lower peak levels. Researchers attributed this slower population growth to increased activity of spiders, mirid bugs, and rove beetles, which continuously suppressed brown planthopper populations throughout the season (Yele et al., 2023). Studies on green leafhoppers also found that combining ecological engineering with biopesticides resulted in much lower pest densities than either preventive insecticide spraying or untreated controls. Natural enemy populations became especially abundant during the later growth stages, suggesting that pest suppression established in the middle season continued into the late season (Rosida et al., 2025). Similar results have been reported for rice leaffolders. Diversified field margins and border planting reduced both pest populations and crop damage. In natural farming systems, border planting with aromatic rice significantly lowered rice leaffolder populations and improved the balance in favor of natural enemies (Chowdhury et al., 2023). 4.3 Reduced risk of late-season pest outbreaks Field exclusion experiments have shown that when natural enemies are removed from rice fields, brown planthopper populations increase rapidly and cause much greater yield losses. These results demonstrate that a complete natural enemy community is one of the most important ecological safeguards against late-season pest outbreaks (Ali et al., 2023). Conserving beneficial insects while reducing unnecessary chemical disturbance helps maintain a more stable and resilient rice ecosystem. Once this ecological balance is disrupted, secondary pest outbreaks, resurgence of minor pests, and the development of pesticide resistance become much more likely. Late in the growing season is usually the period when planthoppers, rice leaffolders, and stem borers reach their highest population levels. Therefore, the ecological stability established during the early and middle growth stages largely determines whether severe pest outbreaks occur later. Long-term monitoring studies have shown that many major rice pests reach their annual peak from late tillering through heading and grain filling. Peak populations of brown planthoppers, rice leaffolders, and stem borers generally occur between September and October (Panse and Sharma, 2026). Ecological engineering, bio-intensive integrated pest management (BIPM), and IPM all increase the diversity, evenness, and effectiveness of natural enemy communities. As a result, pest population peaks become lower and crop damage is reduced (Reddy et al., 2024). Field studies conducted in Bangladesh, China, and other countries found that ecological engineering not only reduced pest density but also lowered the occurrence of severe crop damage and decreased the risk of yield loss during the late season (Ali et al., 2019). Participatory ecological engineering demonstration programs also reported lower populations of planthoppers and stem borers together with larger populations of natural enemies. These results indicate that stable ecological regulation can replace emergency pesticide spraying as the main strategy for managing late-season rice pests (Shanmugam et al., 2022). 5 Effects on Yield Performance and Sustainable Production 5.1 Better plant health Field studies have shown that eco-friendly pest management improves rice plant health by reducing pest damage
RkJQdWJsaXNoZXIy MjQ4ODYzNA==