Western Corn Rootworm (Diabrotica virgifera virgifera LeConte) and Southern Corn Rootworm (Diabrotica undecimpunctata howardi Barber) Identified as Vectors of Late-Season Decline Disease-Causing Pantoea ananatis

Pantoea ananatis was recently described as the causative agent of late-season decline, a new bacterial disease first observed affecting field corn plants, in the Texas Panhandle. The rapid spread of the disease throughout the region and the patchy distribution of symptomatic plants in affected fields, as well as routine observations of edge effects, in which plants with severe symptoms are observed on the edges of affected fields, led us to hypothesize that vectors might be involved in the dissemination of the disease pathogen. In this study, we investigated the western corn rootworm (Diabrotica virgifera virgifera LeConte) and southern corn rootworm (Diabrotica undecimpunctata howardi Barber) for any naturally occurring association with P. ananatis and potential to acquire and transmit the bacterial pathogen. Additionally, we investigated the transgenic corn encoding insecticidal Bacillus thuringiensis proteins (Bt) pyramided with RNAi interference anti-rootworm technology for its potential to protect against any larval role in the transmission of the pathogen through their feeding activities on corn roots. We successfully recovered naturally occurring P. ananatis from samples of both rootworm species collected from corn plants in the field. Following acquisition assays, the acquired pathogen was successfully recovered from previously P. ananatis-free adult rootworms, their eggs, as well as first-instar larvae, suggesting an affinity of the bacteria to establish an endosymbiotic and transovarial association with both rootworm species. Additionally, the transgenic Bt corn with RNAi anti-rootworm technology was ineffective in preventing the transmission of the pathogen by the infected larvae. Findings from this study confirm a vector role in the transmission of the disease pathogen.