Tiny guards of pomelo orchards

In agricultural production, the prolonged overuse of plant protection products (PPPs) has diminished populations of natural enemies, allowing pests to proliferate more easily and become harder to control. Restoring and utilizing beneficial organisms is considered an effective biological solution to address these challenges. This has been clearly demonstrated by a pilot model deploying weaver ants to control pests on pomelo trees in Thien Tin commune, Quang Ngai province, recently implemented by the Central Region Plant Cultivation and Plant Protection Center.

In recent years, pest infestations have significantly reduced yields of citrus crops, including pomelo. According to the Center, before launching the model, technical staff surveyed 20 pomelo-growing households to assess cultivation practices and pest control habits. Results showed that although 100 percent of farmers had received technical training, the application in practice remained limited, with heavy reliance on pesticides still common.

Based on these findings, the model was designed in a structured manner, focusing not only on introducing weaver ants into orchards but also on transferring technical knowledge and shifting farmers’ awareness. A training session for 35 farmers was organized, providing guidance on breeding and managing ant colonies, as well as on applying principles of integrated pest management and integrated plant health management (IPM/IPHM).

The participating orchards consisted of pomelo trees aged between five and seven years, a stable growth stage suitable for evaluating the model’s effectiveness. Before releasing the ants, farmers were instructed to stop using pesticides, clean their orchards, and create favorable conditions for ant development, such as connecting tree canopies and supplementing natural food sources when necessary.

The model was set up as an experiment with different treatments: releasing three, six, and ten ant nests across 30 trees, along with a control group without ants. This approach allowed for accurate evaluation of appropriate release density to ensure long-term effectiveness and scientific validation for scaling up. Field workshops and regular evaluations were also conducted, enabling farmers to directly observe, compare, and exchange experiences.

As one of the participating farmers, Pham Thinh from Ngoc Son hamlet said his orchard had previously been heavily affected by leaf miners, thrips, and mealybugs. Despite using biological pesticides as recommended, results were inconsistent.

“Since applying the weaver ant model, I have almost stopped spraying pesticides. The ant colonies are thriving and effectively eliminating pests, helping the pomelo trees grow healthier. Pesticide use has dropped by about 80 to 90 percent. This change not only reduces input costs but also protects farmers’ health and produces safer fruit for consumers,” Thinh said.

Toward sustainable citrus production

Monitoring results from the Central Region Plant Cultivation and Plant Protection Center show that orchards with weaver ants recorded clear improvements in pest conditions. Mealybug populations declined steadily across all ant-release treatments, while in the control orchard without ants, pest density increased over time.

Similarly, sooty mold disease, which develops from honeydew secreted by sap-sucking insects, decreased significantly in orchards with ants, while continuing to rise in untreated areas. These findings highlight the important role of weaver ants in orchard ecosystems. By preying on pests, the ants help establish natural biological balance, reducing pest pressure without reliance on chemicals.

In addition to effective pest control, the ant colonies demonstrated stable growth and strong adaptation to local conditions. The number of nests and their distribution increased over time, indicating the potential for long-term sustainability if managed properly.

Among the tested options, releasing three to six nests per 30 trees was found to be the most suitable approach. This density ensures effective pest control while maintaining stable ant populations without excessive competition for food.

Local officials also emphasized the broader environmental benefits of the model. “In the past, farmers depended heavily on pesticides, which significantly affected the environment. With weaver ants, pests are still well controlled without frequent spraying. We hope this model will be expanded so more farmers can benefit,” said Vo Huu Trung, head of Ngoc Son hamlet.

According to the Thien Tin Public Service Center, the commune has favorable natural conditions for fruit production, with pomelo as a key crop contributing to stable incomes for many households. The commune currently has about 100 hectares of fruit trees, with pomelo accounting for a large share.

Initial results from the pilot model in Ngoc Son hamlet have been highly encouraging. Pesticide use has dropped significantly, production costs have decreased, and pomelo quality has improved, leading to stronger market recognition. The model is seen as an important step toward building safe production zones and moving toward sustainable organic agriculture.

When applied on a larger scale, the model not only helps increase farmers’ incomes but also contributes to environmental protection and the restoration of natural ecosystems in farming.

Bui Ngoc Chau, Director of the Thien Tin Public Service Center, said the commune plans to continue working with technical agencies to expand the model beyond pomelo to other key crops, particularly citrus.

Luong Anh Tuan, Director of the Central Region Plant Cultivation and Plant Protection Center, emphasized that the model’s greatest value lies in changing farmers’ awareness and cultivation practices. “It has significantly reduced pesticide use in the fields, thereby improving soil health, protecting the environment, and moving toward sustainable agriculture,” Tuan said.