Department for Environment, Food and Rural Affairs




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Biocontrol methods

Biocontrol methods may be applicable inside or outside the colonies and in the protection of stored comb. However, the applicability of the method depends on both the efficacy and the non-target effects on adult and larval honeybees.




In-hive control

Viruses


A range of viruses have been used for insect control, particularly in developing countries where conventional pesticides are relatively expensive. A review of biological control using viruses is given by Frederici (1999) and summarised here. Viruses, particularly nuclear polyhedrosis viruses (NPVs), are used in the control of lepidopteran (primarly Helicoverpa, Heliothis and Spodoptera) and hymenopteran (sawfly) pests. The only example of viral control of beetle populations has been the use of the non-occluded baculovirus of the palm rhinoceros beetle (Oryctes rhinoceros). The viruses most

Currently registered soil applied insecticides/nematicides

Active ingredient

Application method

Use

1,3-dichloropropene

Ground spray

Nematicide/insecticide

Fosthiazate

Granule

Nematicide/insecticide

Aldicarb

Granule

Insecticide

Benfuracarb

Granule

Insecticide

Carbosulfan

Granule

Insecticide

Chlorpyifos

Drench

Insecticide

Ethoprophos

Granule

Insecticide

Fipronil

Soil incorporated

Insecticide

Imidacloprid

Granule

Insecticide

Oxamyl

Granule

Insecticide

Permethrin

Drench

Insecticide




Drench formulations containing Chlorpyrifos 48% ai nominal

Agriguard Chlorpyrifos

Alpha chlorpyrifos 48EC

Ballad

Barclay Clinch II



Cyren

Chevron 48

Choir

Dursban 4



Dursban WG

Greencrop Pontoon

Lorsban 480

Lorsban T

Lorsban WG

Pyrinex 48EC

Spannit

Standon Chlorpyrifos 48



Talon

Tripart Audax


commonly used for control of invertebrate pest populations have been the NPVs due to their occurrence in pest



populations, ease of production in their hosts, and availability of the technology for their formulation and application. The counter to this is that the NPVs tend to be narrow in their host range and have a relatively slow speed of kill compared with conventional pesticides.

Bacteria


The overwhelming majority of bacteria currently used or under development as microbial control agents for insects are members of the spore-forming species Bacillus (Frederici, 1999). These bacilli occur in both healthy and diseased insects but can also be isolated from soil, plants and aquatic environments.
Bacillus thuringiensis. The primary bacterium used in biological control is Bacillus thuringiensis (Bt) and its use in biocontrol has been thoroughly reviewed (Glare and O’Callaghan, 2000; Entwistle et al., 1993). Bt is a complex of subspecies all of which are characterised by the production of a parasporal body during sporulation and produce both protein endotoxins and nucleotide exotoxins capable of killing insects. They are easy to mass produce, formulate and use and usually kill in less than 48 hours. Thus Bt has been widely applied in pest control. The parasporal body contains one or more protoxin proteins in crystalline form which are activated by protolysis in the insect gut.
Several thousand natural strains of Bt have been isolated from around the world and different sources. The isolates have been classified into 30 serotypes based on biochemical properties and flagellar antigens or H-antigens. However, the classification does not reflect the pathotype of the bacterium which is defined by the δ-endotoxins. These insecticidal proteins are synthesised after stage II of sporulation and accumulate in the mother cell as a crystal which can account for up to 25% of the dry weight of the sporulated cells. Most Bt strains can, in fact, synthesise more than one crystal which may be formed by different, but related, endotoxins. Each type of endotoxin is active against a limited range of insects. The primary endotoxins with activity against coleoptera are class CryIII of molecular weight 66-73 kDa (serotype 8) expressed in B. t. tenebrionis (also known as B. t. san diego and Ecogen strain EG2158) and an unclassified crystal of molecular weight 81 kDa (serotype 3) expressed in B. t. kurstaki JHCC 4835. Ecogen strain EG2838 also shows activity against coleopteran pests although it possesses different endotoxin genes to EG2158. A further Bt strain, donegani, has also been patented with activity against coleopteran pests. Most of the coleopteran species susceptible to B. t. tenebrionis belong to the chrysomelid family with only six species from other families reported as being susceptible. B. t. tenebrionis has been tested against only one species of the family Nitidulidae, Meligethes aenaus, and was reported to have no significant effect in the adults by Meyer (1989) (cited by Keller and Langenbruch, 1993) but both Ferrari and Maini (1992) and Prischepa and Mikul’skaya (1998) (cited by Glare and O’Callaghan, 2000) reported susceptibility. This strain has been reported to have no effects in honeybees (Ferrari and Maini, 1992). B. t. thuringiensis was also reported to have effects on Meligethes aenaus (Prischepa and Mikul’skaya, 1998; Prishchepa and Vanyushina, 1997, cited by Glare and O’Callaghan, 2000). However, B.t. thuringiensis has also been reported to affect honeybees in the laboratory (Glare and O’Callaghan, 2000).
The β exotoxin is far less selective than the endotoxins with 55 species belonging to ten orders of insects shown to be susceptible, however, this includes the honeybee Apis mellifera (Glare and O’Callaghan 2000).
Commercial availability

There are a number of Bt strains which are commercially available (BCPC 2001a).



Bt morrisoni is identified as strains Sa-10 (Certis) and NovoBtt (Valent Biosciences) and sold as Novodor (Valent Biosciences). Applications are required every 7-10 days. The encapsulated δ-endotoxins (CryIIIA) is sold as M-Trak (Ecogen). Bt kurstaki and aizawai strains EG7673 and EG2424 are sold as Raven (EG7673), Lepinox (EG7826), Crymax (EG7841) and Jackpot (EG2424). Bt japonensis strain buibui is specific for beetles, trade name M-Press (Mycogen)

Spiroplasmas


Klein et al. (2002) assessed the effects of five beetle-associated spiroplasmas to a sap beetle (Carpophilus humeralis). Two to five days after oral exposure 4 of the 5 spiroplasmas tested could be recovered from the adult sap beetles. However, there is very limited information to determine whether such an approach could be developed for SHB and, like the introduction of other non-indigenous diseases, a complete risk assessment would be required.

Arthropods


The first line of arthropod defence against the SHB is the honeybee colony itself. The ability of the honeybees within the colony to control any beetles present is important if bees are to be bred with capability of defence against the beetle. The Cape honeybee (A. m. capensis) protects itself by physically ejecting the beetles from the colony and encasing the beetles within the colony with tree resin; up to 200 beetles have been reported encased in this way in a colony (Neumann et al., 2001). The natural defence of the Cape honeybee towards the small hive beetle was shown by Elzen et al. (2001) who recorded 32.8% defensive responses in response to the presence of a small hive beetle introduced into a test cage compared with only 1.4% in European honeybees. The potential role of hygienic behaviour of honeybees in controlling small hive beetle populations, e.g. by removal of eggs and larvae, was investigated by Taber and Hood (2000). They showed no significant difference in the numbers of beetles present in colonies of bees with and without hygienic behaviour genes.
Other arthropods are unlikely to be practical in the control of the small hive beetle within honeybee colonies. Even those that prey on Coleoptera which may be used in controlling larvae searching for pupation sites are not specific to the Nitulidiae and therefore are likely to result in adverse effects on other non-target beetle species (Hagen et al., 1999).
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