- Department:Hazard Control Division
With the seasonal increase in the number of Dolichoderus thoracicus, they are invading farms and residential areas, disrupting agricultural operations and disturbing household living conditions. The Animal and Plant Health Inspection Agency of the Ministry of Agriculture and the Chemicals Administration of the Ministry of Environment held a joint press conference on Dolichoderus thoracicus control today (26th), collaborating with expert scholars to jointly advocate: "Environmental and Agricultural Cooperation to Clean Our Homeland - No More Dolichoderus thoracicus Troubles!" To prevent Dolichoderus thoracicus disturbances, emphasis should be placed on environmental sanitation and field management. In agricultural areas, efforts should be intensified to control aphids and scale insects that coexist with the Dolichoderus thoracicus, thereby reducing their population density in the fields. In residential environments, it is important to tidy up water pipes, electrical wires, cables, and other debris to prevent them from invading or nesting. If necessary, household pesticides may be used for control. The Animal and Plant Health Inspection Agency and the Chemicals Administration will jointly conduct educational campaigns to assist local governments in guiding the public on prevention and control measures.
Director General Hsu Jung-bin of the Animal and Plant Health Inspection Agency stated that in recent years, the population of Dolichoderus thoracicus populations has increased in central and southern Taiwan, with distribution ranging from Hsinchu-Miaoli, Taichung-Changhua-Nantou to Yunlin-Chiayi-Tainan, and Kaohsiung regions. The Dolichoderus thoracicus has disrupted farmers' agricultural operations and disturbed residents' daily lives. The Animal and Plant Health Inspection Agency and the Chemicals Administration plan to conduct joint educational seminars in relevant counties and cities during June-July, introduce prevention methods for farmland and residential areas, thereby reducing the inconvenience caused to residents.
Director General Hsieh Yen-ju of the Chemicals Administration reminded the public that there is no other way to prevent Dolichoderus thoracicus in residential areas. The “Three Nos” principle for ant prevention—do not let ants come, do not let ants eat, and do not let ants stay—should be strictly implemented. Environmental cleanup and organization should be prioritized, followed by physical methods. Household pesticides approved by the Environmental Protection Administration should only be used when necessary, or assistance from licensed pest control companies should be sought to effectively prevent and reduce the nuisance caused by Dolichoderus thoracicus.
Deputy Director General Tu Li-hua of the Animal and Plant Health Inspection Agency emphasized that Dolichoderus thoracicus does not directly harm crops and is not classified as an agricultural pest (not belonging to diseases, insects, or weed pests). Therefore, no pesticides are approved for use against this ant species. She recommended that farmers practice good field sanitation management by clearing dead branches and fallen leaves, removing bamboo poles and water pipes to reduce Dolichoderus thoracicus habitat and hiding spaces. Additionally, farmers should actively control aphids or scale insects that coexist with the Dolichoderus thoracicus to reduce their food sources. If necessary, approved pesticides may be used to control aphids or scale insects. For more information, please visit the Pesticide Information Service Network. Moreover, farmers may prepare homemade boric acid sugar water as bait material.
Ant ecology expert Professor Lin Tsung-chi explained that Dolichoderus thoracicus entered Taiwan 200-300 years ago, distributed in low-altitude foothill environments including bamboo groves, mixed forests, and abandoned lands. As a multi-queen population, it can rapidly reproduce and spread in short periods. This ant species has no fixed nests; tree bark crevices, leaf undersides, fruit stem depressions, bamboo tubes, and abandoned agricultural materials can all serve as temporary nests. Even when exposed to external stimuli that reduce their numbers, they can quickly replenish their population. The ants only consume sugar-containing liquids and are easily attracted and aggregated by honeydew from aphids and scale insects in agricultural fields.
Assistant Researcher Yu Yi-chih from the Taichung District Agricultural Research and Extension Station, Ministry of Agriculture, shared examples of Dolichoderus thoracicus management in lychee, longan, and coffee plantations. The primary goal is to prevent ant colonies from disrupting farmers' field operations by controlling aphids and scale insects on crops, reducing honeydew production to avoid attracting ant aggregation, and ultimately reducing the density of Dolichoderus thoracicus in the field. Farmers can prepare homemade boric acid sugar water (boric acid below 3% mixed with 10-20% sucrose water), place it in containers at ant activity sites, and replace it regularly. This method can effectively reduce Dolichoderus thoracicus populations within 1-2 weeks. Additionally, fields should be kept clean, with excess debris removed to reduce hiding places for Dolichoderus thoracicus.
Professor Emeritus Hsu Err-lieh from the Department of Entomology at National Taiwan University stated that Dolichoderus thoracicus is primarily an ecological problem. When their natural habitats in farmlands, forests, and wild environments are disturbed, they may invade residential environments seeking nectar sources, spreading through water pipes, pipelines, cables, and connected tree branches, nesting in high-concealment residential facilities such as ceilings, partition panels, and electrical boxes, causing public living disruptions. It is recommended to maintain a clean and organized home environment, remove unused bamboo poles, plastic pipes, and other items, avoid piling up clutter, dispose of food waste and food scraps, store sugary beverages in sealed containers, and adhere to the “Three Nos” principle for ant prevention. Initial treatment can be performed using diluted soap and detergent water. When necessary, Ministry of Environment-approved household pesticides may be used, or assistance can be sought from licensed pest control operators. Relevant information can be found on the website for inquiring about household pesticide permits and pest control service providers.
The Animal and Plant Health Inspection Agency added that the population of Dolichoderus thoracicus may have increased due to climate change, with distributions spanning from the eastern district of Hsinchu City, Xihu Township in Miaoli County, along the Baiguashan Mountain Range, to Chiayi County and Yunlin County. These ants disrupt farmers' harvesting and other agricultural operations in farms. The Animal and Plant Health Inspection Agency has prepared relevant infographic cards for farmers to reference, with agricultural research and extension stations assisting in guiding farmers in proper field management. The Chemicals Administration reminded that for potential Dolichoderus thoracicus hiding places in residences, environmental cleanup should be conducted first. When Dolichoderus thoracicus invasion is discovered, diluted soap and detergent water or household pesticides may be sprayed at doorways, windows, pipelines, electrical cables, bamboo poles, and utility poles to form barrier zones. Apply the same method indoors for pest control. When necessary, qualified pest control operators may be sought. The Ministry of Environment has currently approved 9 household pesticides for public use. In the future, the Animal and Plant Health Inspection Agency will collaborate with agricultural research and extension stations and the Ministry of Environment to conduct educational seminars in relevant counties and cities, strengthening public understanding and application of Dolichoderus thoracicus control methods, jointly reducing the impact of Dolichoderus thoracicus on agricultural operations and residential living.
