Enhanced toxicity of Bacillus thuringiensis subspecies kurstaki and aizawai to black cutworm larvae (Lepidoptera: Noctuidae) with Bacillus sp. NFD2 and Pseudomonas sp. FNFD1.

Bacillus thuringiensis subspecies kurstaki and aizawai are important control agents for lepidopteran pests. Bioassays were designed to test B. t. kurstaki and aizawai against second- and-fourth instar black cutworm larvae with and without Bacillus sp. NFD2 and Pseudomonas sp. FNFD1 bacteria. B. thuringiensis subsp. aizawai (XenTari) was more toxic to both second- and fourth-instar black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), larvae than B. t. kurstaki (DiPel) at 7 d after treatment (DAT). When DiPel was combined with NFD2 or FNFD1 versus second instars, the LC50s were 5.0X and 4.7X lower, respectively, than with DiPel alone. DiPel combined with both NFD2 and FNFD1 versus second instars resulted in an LC50 value 7.7X lower than with DiPel alone. When XenTari was combined with NFD2 or FNFD1 versus second instars, the LC50s were 5.2X and 3.8X lower, respectively, than with XenTari alone. XenTari combined with both NFD2 and FNFD1 versus second instars resulted in an LC50 9.7X lower than with XenTari alone. When DiPel was combined with NFD2 or FNFD1 versus fourth instars, the LC50s were 4.4X and 3.4X lower, respectively, than with DiPel alone. DiPel combined with both NFD2 and FNFD1 versus fourth instars resulted in an LC50 5.0X lower than with DiPel alone. When XenTari was combined with NFD2 or FNFD1 versus fourth instars, the LC50s were 5.7X and 3.3X lower, respectively, than with XenTari alone. XenTari combined with both NFD2 and FNFD1 versus fourth instars resulted in an LC50 6.7X lower than with XenTari alone.