Sprays of Bacillus thuringiensis subsp. thuringiensis (B.t.t.), which contained the beta-exotoxin, were applied to small-scale field plots of tomatoes infested with the Colorado potato beetle [Leptinotarsa decemlineata (Say)] and to bean plots infested with the Mexican bean beetle (Epilachna varivestis Mulsant). Two parasitic wasps of the family Eulophidae were used in conjunction with the B.t.t. in an effort to reduce beetle populations. Treatments on tomatoes consisted of either B.t.t. alone, B.t.t. plus releases of the egg parasite Edovum puttleri Grissell, E. puttleri releases alone, or untreated controls. Treatments on beans were similar except the larval parasite Pediobius foveolatus (Crawford) was released instead of E. puttleri.
Treatments in which B.t.t. was used, either alone or in combination with the parasite, significantly reduced adults and 3rd and 4th instar larvae of both species of beetles. The egg parasite, E. puttleri, was unable to significantly reduce the CPB population by itself, however P. foveolatus was able to significantly reduce both 3rd and 4th instar larval and adult populations of the MBB.