Rhizobacteria modulates the oviposition behavior of corn earworm In sweet corn

Plant Growth-Promoting Rhizobacteria (PGPR) represents specific strains of root-colonizing bacteria that can elicit increased plant growth rates, suppress soil pathogens, and induce systemic resistance against plant diseases and insect herbivores. Little is known about the effect of PGPR on the oviposition preferences of female insects. Here we hypothesize that PGPR treatment of sweet corn (Zea mays) affects the oviposition behavior of corn earworm (Helicoverpa zea) and interferes with the feeding behavior of its immatures. To test this hypothesis, sweet corn plants treated with two blends, a single strain, and the untreated control were used in the no-choice oviposition preference test. Blend 5 consists of PGPR strains AP 209 and AP 136, whereas Blend 8 consists of three strains AP 136, 218, and AP 219, and single strain AP136 were used in the experiment. The corn earworm exhibited reduced oviposition on sweet corn plants treated with select PGPR (Bacillus spp.) strains compared to untreated plants. Moreover, the leaf area damage inflected by the larvae was higher in untreated corn plants when compared with the PGPR-treated plants. Interestingly, there was reduced leaf area damage on the single strain treated plants, but there were high number of eggs were laid. When this single strain blended with other strain showed both a reduced number of eggs laid by the female corn earworm moths and less leaf area damage inflected by the larvae. These preliminary findings reveal that the treatment of plants with rhizobacteria may induce significant physiological changes with potential ramifications for plant-insect interactions.