Pest insect infestation in crop fields has now become one of the major challenges in agriculture. If we consider about rice cultivation, problems are mainly classified into two types: biotic (biological) and abiotic (environmental). Biotic problems include various diseases caused by bacteria, fungi, and viruses, such as blast, brown spot, sheath rot, and bacterial leaf blight (BLB).Insect attacks are also a biotic factor and significantly reduce rice yield. Due to insect infestation, rice yield decreases by about 15% in the Boro season, 24% in Aus, and 18% in Aman. On average, considering all three seasons, rice production is reduced by approximately 18% because of insect-related damage.
Hundreds of arthropod species inhabit the rice ecosystem and adopt diverse strategies to complete their life cycles. They function as herbivores, predators, parasites, pollinators, decomposers, and contributors to nutrient cycling. Among them, species that directly feed on rice plants are identified as pests. Scientists of the Entomology Division of the Bangladesh Rice Research Institute (BRRI) have identified 232 insect pests of rice. Of these, about 20-33 species cause economic damage to rice in Bangladesh.These harmful insects are naturally attacked by various predators and parasitoids, which suppress their abnormal population growth and help maintain ecological balance. Approximately 375 species of predators and parasitoids known as beneficial or "friendly" insectsexist in rice fields.
There are different options for pest management. Among these eco-engineering, or ecological engineering is most environment friendly and cost-effective approach.It is an approach that integrates engineering principles with biological technologies to manage insect pests while conserving plants, wildlife, and biodiversity. This method increases food and shelter for beneficial insects and helps maintain ecological balance. In the rice ecosystem, cultivating nectar-producing vegetables, fruits, and flowers on the bunds (field margins) of paddy fields to provide habitat and food for beneficial insectsthereby controlling harmful pestsis known as eco-engineering. Eco-engineering or ecological engineering is a method that combines engineering technologies with biotechnology to control pests while conserving flora and fauna and protecting biodiversity. As a result, food and shelter for beneficial insects increase, ensuring environmental balance.
In the rice ecosystem, eco-engineering refers to controlling harmful insects by creating habitats and food sources for beneficial insects through the cultivation of nectar-producing vegetables, fruits, and flowers on rice field bunds. For example, marigold, cosmos, vegetables, pulses, oilseed crops, hyacinth bean, mung bean, sunflower, and similar flowering plants provide shelter and nectar for beneficial insects. Predators and parasitoids of major rice pests-such as brown planthopper, green leafhopper, leaf folder, and stem borer-feed on nectar from these flowers, survive, and suppress pest populations. Consequently, rice can be produced without using toxic insecticides, without any reduction in yield.
Thus, by cultivating flowers on field bunds to enhance natural enemies of pests, rice production without insecticides becomes possible in Bangladesh. This pest management approach through flower cultivation on rice field bunds is known as eco-engineering.
Let us know the benefits of eco-engineering in the rice ecosystem. Scientists from the Entomology Division of BRRI have been successfully controlling major rice pests during the Boro season since 2015-2025 by cultivating marigold, cosmos, and sunflower as bund crops. Currently, rice production is heavily dependent on excessive insecticide use, posing serious threats to the environment and human health. Alternative methods are therefore essential.
At BRRI, Gazipur, scientists have achieved success in pest control without insecticides using the eco-engineering approach. When colorful, nectar-rich flowers (such as marigold, cosmos, sunflower, sesame, linseed, etc.) are cultivated on rice field bunds, natural enemies of rice pestsknown as beneficial insectstake shelter in these plants, feed on nectar, and reproduce rapidly.
Eco-engineering is not only environment friendly but also, it's an opportunity for farmerto get some additional income. It offers farmers additional income from flowers, pulses, and oilseed crops grown on otherwise unused bunds. Excessive insecticide use has reduced beneficial insect populations in nature. Research further shows that refraining from insecticide application for 30-40 days after transplanting rice seedlings allows beneficial insect populations to increase, keeping pest damage below the economic threshold level.
Under such conditions, cultivating flowers on bunds helps attract beneficial insects. These insects take shelter and feed on nectar from the flowering plants. As soon as harmful insects enter the rice field, beneficial insects quickly detect them and destroy them in various ways-either by directly preying on them or by laying eggs on their eggs-thereby suppressing pest populations without insecticides.Beneficial insects destroy pests through multiple mechanisms. For example, the parasitoid Trichogramma zahiri lays its eggs inside the eggs of the rice leaf folder, destroying about 87% of the pest's eggs.
Let us focus on some success stories ofeco-engineering research in different countries. Over the past decade, countries such as Vietnam, China, and the Philippines have achieved success in controlling rice pests using eco-engineering. Professor Dr. Geoff Gurr of Charles Sturt University, Australia, worked for four years to disseminate this method at the field level in Vietnam, China, and the Philippines. Analysis of his research results shows that eco-engineering can reduce rice pest incidence by 50%, decrease insecticide use by 70%, and increase rice yield by 7%.This approach also increases populations of soil-dwelling insects (detritivores), enhancing soil fertility. Given that rice fields in Bangladesh are fragmented into small plots, the potential for successful pest control through eco-engineering is particularly high.
BRRI research indicates that compared to insecticide-treated rice fields, fields with flowering plants on surrounding bunds have higher populations of beneficial insects and parasitoids. Rice yields obtained with four insecticide applications can be achieved equally by cultivating flowering plants on field margins without insecticides.
Therefore, rice farmers can cultivate nectar-producing flowers (such as marigold and cosmos) on bunds instead of using insecticides. This will reduce production costs and protect the environment from the harmful effects of pesticides. In addition to nectar-producing flowers, commercial flowers like sunflower can also be used. Moreover, cultivating sesame, climbing beans, and mung bean on bunds can increase crop diversity, conserve beneficial insects, and generate additional income.
According to information presented at a recent seminar titled "Mitigating the Risks of Pesticides" held in Dhaka, the current pesticide market in Bangladesh is worth approximately BDT 50 billion. Over the last five years alone, pesticide use has increased by 81.5 percent. While pesticide consumption was about 4,000 metric tons in 1972, it rose sharply to 40,000 metric tons in 2022-23.
As rice is the country's main staple crop, the majority of pesticides are used in rice production. Consequently, the continuous increase in pesticide use poses a serious public health threat to the rice-dependent Bangladeshi population. In this context, reducing the use of pesticidesthrough eco-engineering by the Bangladesh Rice Research Institute represents a major milestone.However, the main challenge to the widespread adoption of this method lies in promoting it at the field level and motivating farmers to refrain from insecticide use.The government should therefore encourage this new innovation and significantly increase research funding in this sector.
The writer is an agriculturist & Senior Communication Officer, Bangladesh Rice Research Institute (BRRI)
