Bio-Blast

The fungus Metarhizium anisopliae has been around for more than 100 years. A very common fungus, it can be found in most people’s backyards. And scientists have known for years that it is a natural predator of termites.

Today, this fungus is available to PCOs in the form of Bio-Blast® Biological Termiticide, sold by Paragon Professional Products. The company launched a national sales campaign for the termite microbial treatment, which has been called an alternative to chemical termiticides for active termite galleries inside a structure. Bio-Blast is also a useful component of an IPM program when used along with monitoring and baiting. The product is marketed by Paragon (800/238-9254) and is available through distributors.

The active fungus in Bio-Blast, Metar-hizium anisopliae, was discovered in 1879 by the microbiologist Eli Metschnikoff and was isolated from the cereal beetle, Anisoplia austriaca. The green fungus occurs naturally in soil throughout the world. There are at least six species of the fungus, infecting more than 200 insect species in seven insect orders (Zimmerman 1993).

Just how effective is Bio-Blast against termites? Research has shown that the product controls subterranean termites, such as Reticulitermes spp., Heterotermes spp., and the Formosan termite, Coptotermes form-osanus. It is also recommended for use against dampwood, drywood and powder-post termites. It can be used in residential dwellings, apartment buildings, commercial establishments, offices, institutions, industrial buildings, warehouses, computer and equipment facilities, greenhouses and schools.

According to EcoScience Corp., East Brunswick, N.J., which developed the formulation especially for termites, Bio-Blast can reach full effectiveness in as little as four to six days, and a termite colony can be eliminated by spraying just 10% of its members. Furthermore, 100% mortality for eastern subterranean or Formosan termites takes about two weeks, the company reports.

Few studies using M. anisopliae have been published by termite researchers independent of EcoScience and Paragon. However, the Australian workers Hänel and Watson (1983) found that adding 20 infected Nasutitermes exitiosus termite workers to 200 healthy workers in laboratory tests resulted in 100% mortality within 14 days. Although some termite species may be more susceptible to the fungus than others, this finding demonstrates that the fungus is transmitted throughout the colony via horizontal transfer. In the field, the exposure percentage needed for 100% elimination likely varies according to species and conditions, but 10% seems to be a good estimate.

The fungal spores kill termites by attaching to and eventually penetrating the exoskeleton. Once the fungus enters the termite, it begins to grow using the termite body as a nutrient source. The termite then dies. In the absence of termites, the fungal spores, deprived of food, expire within 60 to 90 days. The fungus is spread by direct contact, trophallaxis (oral and fecal feeding), and grooming. Termites do not find initial contact with the fungus repellent. When it is contacted, termites carry the conidia back to the nest and spread the infection. Once termites start dying, however, noticeably sick termites are avoided and further spread of the organism is difficult. The technique works because the infection is slow in developing. Field control of an active infestation can take from six or seven days to three or four weeks depending on the size of the infestation, the type of termite, and environmental conditions.

The intensity with which a termite is groomed increases with the number of spores present on the termite’s body. M. anisopliae is extremely infectious, as healthy termites that groom an infected individual for only 15 seconds show “considerable mortality,” according to Kenneth Kramm and David West of the Department of Biological Sciences at Michigan Tech University. What is interesting about the fungus is that it works from the outside. When ingested, spores do not germinate in the termite gut but are excreted unchanged. This allows transfer of the pathogen by trophallaxis, permitting the spread through several termites without inactivation (Kramm and West 1982). Only one germinating spore is needed to kill one termite (Hänel 1981).

FOREST SERVICE FIELD TESTS. Dr. Brad Kard of the USDA Forest Service’s Termite Testing Lab in Gulfport, Miss., has conducted field trials with Bio-Blast. In these tests, 4- x 4- x 12-inch pieces of pine boards were deployed in a checkerboard pattern directly on the ground in an area heavily infested with the eastern subterranean termite, Reticulitermes flavipes. After one year all the boards were found to be heavily infested.

To treat with Bio-Blast, three holes were drilled into each board and the product was injected. After injection, boards were raised onto a brick, covered with another brick, then with a bucket to shade from the sun. Treatments were evaluated by looking at the top and bottom of the board and the brick-board interface for termite activity and tunneling. Of 12 boards treated only with Bio-Blast, termites were present in only one of 12 after one week, representing 92% control. There was 87% subterranean termite control after 97 days. Tunneling activity also decreased with time. With a chemical ground barrier plus an inactive Bio-Blast formulation, there was also 87% control after 97 days. Best results were seen with the Bio-Blast fungus plus a chemical ground barrier: There was no termite activity after 97 days. Untreated boards, water controls, Bio-Blast treatment in contact with the ground and boards covered with buckets all were 100% infested after 97 days.

Extrapolating from his field tests, Kard stated that Bio-Blast is a useful product that kills termites. It is more effective against subterranean termites when used in an IPM program in conjunction with a termite bait or a termiticide barrier. On the basis of his experiment, Kard says, Bio-Blast can be used to kill all the termites within a structure, but “not enough foragers are exposed with current application methods to eliminate a large subterranean colony.” He suggests that Bio-Blast could be especially useful as a treatment in nursing homes, hospitals, and other places where any kind of chemical exposure would be unwise or objectionable.

THE PCO PERSPECTIVE. Experiences of PCOs may be a more relevant measure of efficacy than laboratory tests or limited field tests of this type. Bio-Blast is a wettable powder applied by PCOs with standard chemical sprayers. Termites are treated by spraying the formulation directly into active galleries or mud tubes.

Steve Temple, president of Ocon Termite & Pest Control in Norwalk, Conn., has used Bio-Blast six times, including once as a standalone treatment in a house that had considerable termite structural damage. When structural repairs were made, three months after Bio-Blast had been applied, there were no signs of termite activity in the treated wood. About one year later, a termite swarm occurred. Temple attributes this activity to the fact that Bio-Blast contains no residual. Temple also believes Bio-Blast can be used as an alternative to chemical sprays to kill termites inside a house under certain conditions, such as in sensitive areas. While it may not be suitable for use as a standalone treatment for subterranean termites, he believes it can be used successfully in conjunction with other methods and as long as customers are informed of its limitations.

Bio-Blast effectively eliminates colonies of drywood termites as well as subterranean foragers infesting galleries inside a house. However, because Bio-Blast is a living organism, its activity decays over time. Bio-Blast does not leave a long-term residual as borates do, and thus, it is not a long-term treatment to prevent reinfestation in structures under termite foraging pressure. Therefore, Temple says, Bio-Blast is not a preventive termite treatment but a corrective one to be used when a monitoring method detects a problem.

Dave Tokarz, president of Rocky Mountain Pest Control headquartered in Loveland, Colo., has used Bio-Blast, either alone or along with FMC Corp.’s FirstLine Termite Baiting System, in numerous treatments for more than two years. Tokarz no longer uses any conventional termiticide treatments, and in all cases, the termite being controlled is the western subterranean termite. After treatment, Tokarz monitors with pine stakes or FirstLine monitoring stations and watches for signs of termite activity. In 80% of the cases in which Bio-Blast has been used alone, one treatment has been enough to eliminate all post-treatment signs of termites.

Though Tokarz believes there is much to learn about proper application techniques, he is hopeful that Bio-Blast in conjunction with termite baits and monitoring might be an alternative to chemical barriers. Research has shown that achieving control may be easier in the Rocky Mountain-area because the western subterranean termite has smaller colonies and is less aggressive than the eastern subterranean termite or the Formosan termite.

A NONCHEMICAL CONTROL TOOL. Safety is a key selling point for Bio-Blast. During the last hundred years, the safety of Metarhizium spp. has been tested rather thoroughly. It is nontoxic to birds, fish, mice, rats, guinea pigs and rabbits. Honeybees and earthworms are also unharmed. Because the fungus does not grow at temperatures greater than 95°F, it does not infect humans or mammals. Although Bio-Blast is not directly toxic to humans, allergic reactions may occur if the fungus is directly inhaled. Full toxicity tests have not been conducted for many cold-blooded animals.

Since the formulation is applied as a liquid slurry into inaccessible areas, allergic reactions will probably not be a problem with homeowners. However, when the formulation is applied in living areas, operators are cautioned not to leave residues on exposed surfaces or introduce the material into the air. Since breathing dust could cause an allergic reaction, contact with skin, eyes and clothing should be avoided. All the reasonable precautions that PCOs normally take should be followed.

Difficulties in achieving control with Bio-Blast are sometimes due to a lack of proper education about the product. The application of living organisms requires a slightly different mindset and approach from that used when applying a chemical barrier. Failures have occurred when active galleries were not reached by the spray technique. Holes must be drilled in wood where active galleries are present, and nozzles of the proper length and size to reach the infestation must be used.

Bio-Blast is applied only in mud tubes and active galleries. If the product is eventually adapted for use in soil treatments, the approach will likely evolve along the lines of DowElanco’s Sentricon System, as opposed to conventional soil treatments. Bait or monitoring stations would be established around a building’s perimeter, with the product being applied after termites are found.

Bio-Blast represents an effective alternative to chemical treatments for clients who have special sensitivity or will not permit chemical applications. Properly applied, Bio-Blast is as effective as chemicals for treatment of drywood colonies. Unless at least 10% of foragers can be directly dusted with the formulation, however, Bio-Blast will not kill an entire subterranean colony. For complete control of subterraneans, an IPM program consisting of monitoring, baiting and Bio-Blast treatments is necessary.

Dr. William Quarles is managing editor of the IPM Practitioner, based in Berkeley, Calif.

References

Hänel, H. 1981. A bioassay for measuring the virulence of the insect pathogenic fungus Metarhizium anisopliae (Metsch.) Sorok. (fungi imperfecti) against the termite Nasutitermes exitiosus (Hill) (Isoptera: Termitidae). Z. Ang. Ent. 92:9-18.

Hänel, H. and J.A.L. Watson. 1983. Preliminary field tests on the use of Metarhizium anisopliae for the control of Nasutitermes exitiosus (Hill) (Isoptera: Termitidae). Bull. Entomol. Res. 73:305-313.

Kramm, K.R. and D.F. West. 1982. Termite pathogens: effects of ingested Metarhizium, Beauveria, and Gliocladium conidia on worker termites (Reticulitermes sp.). J. Invert. Pathol. 40:7-11.

Zimmermann, G. 1993. The entomopathogenic fungus Metarhizium anisopliae and its potential as a biocontrol agent. Pesticide Science 37:375-379.

STORAGE, APPLICATION, AND DISPOSAL OF BIO-BLAST

Microbials have some advantages over conventional pesticides in the realm of disposal. Wastes resulting from the use of Bio-Blast can be disposed of on site or at an approved waste disposal facility. According to EcoScience, empty Bio-Blast foil containers can be safely added to trash.

Bio-Blast is supplied in 19-gram foil packets containing a 50/50 mixture of Metarhizium anisopliae conidia and a dry inert powder. Each gram of the formulated product contains 4 billion viable conidia. For all treatments, a watery paste containing a 0.5% active ingredient concentration of Bio-Blast is prepared. The entire contents of one foil packet is added to about 16 ounces of water to make a slurry. The slurry is then poured into a clean sprayer and enough water is added to yield 64 ounces of liquid. The suspension is also agitated to ensure proper mixing.

Infested areas are sprayed with a sufficient amount to thoroughly penetrate and cover the area to the point of wetness, avoiding runoff. The suspension of spores remains viable for one day. Any unused dry material in an opened pouch should not be used after one day. The product’s shelf-life is about two years, according to EcoScience.

Although it is easy to use, Bio-Blast has slightly different handling requirements than conventional pesticides because it contains a live biological agent. For instance, a clean sprayer must be used for application, as contamination of equipment with insecticides, fungicides or borate termiticides may inactivate the fungus. Bio-Blast cannot be mixed with other pesticides and must not be formulated into other end-use products.

According to EcoScience product directions, for the control of termites in accessible, localized areas of infested wood, a 0.5% dilution of Bio-Blast is applied to galleries and voids in damaged wood and surrounding areas where wood is vulnerable. These sites include galleries and voids in sill plates, piers, girders, subfloors, floor joists, door and window frames, wood trim and any infested area which is exposed to access by termites from the soil or other points of entry. A sufficient amount is sprayed to penetrate and thoroughly wet the area, avoiding runoff.

Applications may be made to infestations which are difficult to reach or inaccessible by drilling holes approximately 5 to 10 inches apart and injecting a 0.5% dilution into the damaged wood or void spaces. Multiple holes may be drilled into the infested or vulnerable areas; however, treating one hole before the next is drilled will increase penetration of Bio-Blast into the target area. A sufficient amount of spray is injected to penetrate or cover the treatment area. Once the application has dissipated into the target area, a repeat application may be made to enhance penetration and coverage. Treatments are repeated as necessary to maintain control.

Termites in trees, stumps, utility poles, fencing, decking materials, construction materials, sign posts and other similar elements may be treated by drilling holes approximately 5 to 10 inches apart into the interior of the infested areas. Horizontal holes approximately 4 to 10 inches apart may also be drilled in a circular fashion around stumps, trees, utility poles and other similar sites. A sufficient amount of a 0.5% dilution is injected to thoroughly penetrate the target area. Termite carton nests in trees, structures or other areas may be injected with a 0.5% dilution using a pointed injection tool. Termites in mud shelter tubes may be treated by injection or with a coarse fan spray. Tubes should be injected or sprayed with sufficient pressure to break open the tubes. The formulation should not be applied to crawlspaces of plenum-style houses.

Detailed use instructions for Bio-Blast can also be found on the Web at www.ecosci.com.