Transmission of Pantoea ananatis, the causal agent of leaf spot disease of maize (Zea mays), by western corn rootworm (Diabrotica virgifera virgifera LeConte)

The aim of this study was to determine the role of Diabrotica virgifera virgifera (western corn rootworm, WCR) as a potential insect vector of the pathogenic bacterium Pantoea ananatis. The experiment included a greenhouse test to investigate if WCR was able to transfer the pathogenic bacteria from infected to healthy maize plants. Adult WCR specimens collected from maize fields near Rzeszow were used in the experiment. The plant materials were sweetcorn plants of the Waza variety. Pure cultures of previously verified P. ananatis strain M241 were the source of the inoculum. Insects caught under natural conditions were incubated in an isolator containing pathogen-negative plants. Randomly selected insects were then examined for the presence of bacterial pathogens of maize in their digestive tract. Pathogen-negative insects were used in the next stage of the experiment still carried out in isolators, in which the insects foraged on maize seedlings previously infected with P. ananatis. The control group consisted of healthy, uninfected insects and plants. After the incubation period, the presence of bacterial pathogens in the gastrointestinal tract of the WCR specimens was confirmed. Subsequent insects that acquired P. ananatis were bred on pathogen-negative maize plants. After incubation, the presence of pathogenic bacteria in the body of the examined WCR beetles was confirmed, and the presence of symptoms of the bacterial disease was noted on maize plants, fulfilling Koch's postulates and indicating that the WCR is a vector of P. ananatis on maize plants. This is the first report on the vectorization of P. ananatis by D. virgifera globally.

Automated summary

This study confirmed the role of western corn rootworm as a vector of Pantoea ananatis, providing the first report of vectorization of P. ananatis by D. virgifera globally.