Termites Control Tutorial (Second Edition)

Author: Dai Zirong et al. / Country:
Publisher:
Publishing Time: 2002-04-01
Features: From the termite breeding analysis table for embankments, it can be seen that the general principle for termite control of embankments should be "early treatment when termites are present and early prevention when termites are absent." If a newly built embankment or an embankment that has been thoroughly treated for termites has a mature termite nest nearby with winged adults that can fly to the embankment body, with an annual dispersal of 1,000 pairs and a survival rate of 0.1% to 0.2%, by the 10th year, there will be 10 to 20 termite nests within the embankment. If the juvenile nest period is a 10-year cycle, then from the 11th year onwards, mature termite nests that participate in dispersal will also mature and join the cycle. By the 20th year, there will be 75 to 260 termite nests within the embankment, including 12 to 26 mature nests. By the 30th year, the cumulative number of nests within the embankment will reach 460 to 2,660, with 12 to 314 mature nests. This calculation is based on a single colony; otherwise, the situation would be even worse. For example, in the Longhuai Reservoir of Liujiang City, Guangxi, from October 1992 to July 1993, 105 pieces of charcoal fungus grew from termite nests on a 155m earthen embankment, with an average of one nest every 1.5m. In the Gongqiao demonstration site in Huazhou County, Guangdong, within a 5.4km embankment section, over 900 nests were destroyed in a year. Therefore, for newly built embankments and embankments that have been thoroughly treated and are free of termite infestation, as long as there are termite breeding sources around the project, continuous trapping and eradication of termites in the source areas must be carried out to maintain the excellent environment of termite-free embankments. Current practices in termite control of embankments have proven that for a 1km embankment or an earthen dam, as long as 400 to 800 effective workdays are invested within two years, it can be thoroughly treated. In terms of prevention, there is no one-time solution; only continuous trapping and eradication of termites in the source areas can address the issue. In summary, termite control is a long-term task. In water conservancy projects, it can transition from termite control to prevention-first, shifting the main focus of control away from the embankment and adopting a proactive prevention strategy. This involves eliminating termites without filling nest cavities, using ASP baiting and ASP-type killing sheets to implement "baiting to locate, then kill or bait and kill combined" techniques, and eliminating termite harm in the juvenile stage to ensure a long-term excellent environment free of termites and embankment safety.
III. Exploration of Water Conservancy Termite Control Techniques
The termite control efforts in the Guangdong water conservancy industry began in the early 1950s, with large and medium-sized embankments like the Beijiang Embankment starting early in 1954. After the National Termite Control Experience and Academic Exchange Conference in Shashi in 1960, some key embankment counties in Guangdong began to pay attention to termite control. In 1964, the Qingyuan County Science and Technology Commission invited expert Li Shimei from the Provincial Entomological Institute to hold a training session for 50 participants, while also establishing a termite control research institute to assist the county's water conservancy bureau in termite eradication efforts. In 1965, the Qingyuan County Yingzui Reservoir implemented blacklight trapping of winged adults and toxic soil anti-termite measures, which were widely adopted in southern provinces. Combined with the extensive use of traditional methods such as probe excavation, liquid and paste injection, and smoke fumigation, the late 1970s saw the summary of what were then considered effective "find, dig, kill, and inject" methods. Although some nests were treated, the methods were labor-intensive, yielded poor results, and severely polluted the environment. Blacklight trapping, in particular, became a "wolf at the door." Local prevention teams were not well-established, and there was a lack of top-down management structures, relying solely on private house termite control personnel and research institutions. As a result, termite control efforts could not be effectively implemented, and termite infestations became increasingly severe. With the increasing number of earthen dams being built, the task of termite control became more burdensome, even by the 1980s when new technologies had already proven effective, incidents such as the "8607" typhoon and the "6·5" flood in 1987 still occurred. Many embankments built in the 1950s and 1960s had reached the 10 to 30-year mark by the 1970s and 1980s, entering the peak period of severe termite infestation according to the life cycle of embankment termites. A series of reservoirs, including Hedian, Gaozhou, Yantian, Yangmei, Jiandong, Hexi, and Tiegang, experienced leakage and safety hazards due to termite infestations between 1970 and 1975. In September 1970, the Hejiang medium-sized reservoir collapsed, destroying an entire village, but the cause remained unclear, causing widespread panic among downstream residents. Some large and medium-sized reservoirs had to restrict water storage for long periods, affecting economic and social benefits. This finally drew attention, and termite control was gradually included in the agenda.
The exploration of water conservancy termite control has been long and extensive, involving the use of various chemical drugs and methods. The following four methods, once widely used, all have severe flaws.
1. Nest Excavation and Eradication
Nest excavation is an old, backward, and primitive method. It is labor-intensive, damages the embankment, and is difficult to completely excavate. Only the main nest can be filled, leaving most of the fungal chambers and multiple leakage channels as hidden dangers. Therefore, after excavation, additional grouting and reinforcement of the embankment are required, incurring significant costs. The rate of nest excavation cannot keep pace with the natural breeding rate of termites, leading to recurring infestations even in years, making control and prevention efforts futile. Since the 1980s, with the adoption of the Apistan baiting method and the development of the "three-link eight-step" and "baiting to locate, then kill or bait and kill combined" systematic prevention and control technologies (promoted measures), nest excavation has gradually become a thing of the past in Guangdong. It is only allowed for teaching, scientific research, and certification purposes.
2. Smoke or Liquid Injection Eradication
This method was used before the baiting method was developed as a substitute for nest excavation. Toxic agents such as DDT powder, lead phosphide, sodium pentachlorophenate, and dichlorvos emulsion were mixed into smoke agents or liquid solutions and injected through termite galleries. However, termites are naturally hidden and sensitive, making it difficult to reach main galleries, and their random gallery paths and worker termites' tendency to block passages result in low eradication effectiveness. The method also pollutes the environment and poses health risks to operators. After eradication, prompt filling of cavities is still required, making it even less acceptable than nest excavation. It has long been phased out.
3. Grouting Eradication
Since the 1970s, due to insufficient justification for grouting and reinforcement for other engineering quality issues, termite infestation was used as a reason to include it in projects, and its achievements were exaggerated in post-construction summaries to showcase the results of grouting reinforcement. If an embankment requires grouting and reinforcement due to quality issues, intentionally filling dead nest positions with grout after baiting can be reasonable and effective for water conservancy projects. However, this should be grouting after eradication, not grouting for eradication. Due to worker termites blocking passages, not only must the grouting be done according to the specifications of reinforcement grouting engineering, but the holes must be drilled to a depth of 4–6m below the surface with a spacing of about 5m, which is impossible for termite eradication. In the past, the Beijiang Embankment under Guangdong's jurisdiction and the city's reservoirs conducted repeated grouting, but termite infestations persisted, as evidenced by examples. Even if galleries are found or grouting is injected through swarm holes to identify nest areas, worker termites can block passages, and due to the special structure of termite nests (as described in the fourth point), grout cannot reach the main nest, rendering it ineffective.
4. Cracking Grouting Eradication
This method was recently promoted with cracking grouting technology, but its effectiveness has not been verified through dissection. Cracking grouting utilizes the stress distribution of the embankment body, believing that applying a certain grouting pressure can split the embankment along its axis, while simultaneously injecting appropriate slurry to form a continuous impermeable mud wall. If there are termite galleries penetrating the embankment, they will inevitably intersect with the continuous impermeable wall. Under pressure control, slurry will enter the nest system, and with the addition of chemicals, termites can be eradicated or cavities can be filled after eradication. In reality, this is not the case. First, only 20% of termite nests are found to have galleries penetrating the embankment, while 80% of nests without such galleries cannot be targeted. Second, among the 20% with penetrating galleries, if the nests are alive, worker termites will block passages, preventing grouting. If the nests are dead, due to the special structure of termite nests and poor filling, as evidenced by several dead nests in the Chisha Reservoir of Shantou City in 1995 that grew charcoal fungus, grouting cannot be effectively filled. Cracking grouting is suitable for addressing large-scale hidden dangers where the specific problem areas cannot be determined. However, current termite control technologies are fully capable of accurate and efficient eradication, with baiting methods achieving 100% success and nest grouting filling rates exceeding 95% when implementing the "three-link eight-step" technical measures. Spending huge sums on cracking grouting for termite control is neither feasible nor guaranteed to fill dead nest cavities effectively, making it unacceptable.
"First eradicate termites, then grout" is a conclusion drawn from years of practical experience by water conservancy termite control workers in Guangdong. It is a theoretical application of termite biology to engineering technology. Like the entire systematic prevention and control theory of water conservancy termites, it is established through practical verification.