Termites bioassays

Termite Bioassays. Multiple choice tests were conducted using wood blocks of birch, red oak, redwood and Alaska yellow cedar where blocks were decayed by P. chrysosporium for either 3,8, or 12 wk. Bioassays were conducted using rectangular Rubbermaid storage containers (14.5 cm X 8.5 cm X 4 cm) (Consolidated Plastics, Twinsburg, Ohio). Each container served as a replicate and was filled with 100 g of sand (Standard Sand and Silica Company, Davenport, FL) moistened with 20 ml of water. Each container had four 2-cm diameter holes, one hole on each side. A 14 ml (17 x 100 mm) polystyrene round-bottom Falcon test tube (Becton Dickinson, Franklin Lakes, NJ) was inserted into each hole and sealed in place using a glue gun. The position of treatment tubes was alternated between replicates to preclude any positional effects. Two hundred termites (190 workers 10 soldiers) were placed in the center of each container. The termites were able to move freely between the container and the tubes. 

A wood block was placed in each tube. Each of the four tubes contained a block from a different wood species. These experiments lasted for 3 wk and at the end of each experiment, the number of termites in each container (replicate) was counted. Wood blocks were cleaned and oven-dried at 90° C for 24 h and then weighed. Weight loss due to termite feeding on decayed blocks was determined by comparing wood weights taken after blocks were decayed for 3, 8, or 12 wk with weights of wood blocks at the end of the feeding bioassays. For experiments where blocks were decayed for 3 or 8 wk, there were 12 replicates, with three replicates each from four termite colonies. For the experiment where blocks were decayed for 12 wk, there were 24 replicates, with six replicates each from four termite colonies. 

Termite Antifeedant Choice Bioassay Two filter paper disks (2cm diam.) were treated with 25 pi of extract or solvent (acetone or methanol) in three replicates (250 pg/disk), and placed on moistened sand in 55 mm diam. petri dishes, with 30 Reticulitermes speratus workers. After 2 weeks, the amount of feeding on each disk was recorded using video image analysis (as described above). The same antifeedant index as in the leaf-disk bioassay was calculated. 

Specialized substrates include twigs for bioassays of sawflies (All Benjamin 1976 Ohigashi et al. 1981) and bark beetles (Ascher et al. 1975). Blocks of wood (Lenz Williams 1980), board, logs, and paper towel disks (Rust Reierson 1977) have been used for bioassays involving termites. The original references should be consulted for detailed descriptions of methods. 

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