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Title: Potential for Nezara virdula (Hemiptera: Pentatomidae) to Transmit Bacterial and Fungal Pathogens into Cotton Bolls

item Medrano, Enrique - Gino
item Esquivel, Jesus
item Bell, Alois - Al
item Lopez, Juan De Dios

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2009
Publication Date: 10/1/2009
Citation: Medrano, E.G., Esquivel, J.F., Bell, A.A., Greene, J., Roberts, P., Bachelor, J., Marois, J.J., Wright, D.L., Nichols, R.L., Lopez, J. 2009. Potential for Nezara virdula (Hemiptera: Pentatomidae) to transmit bacterial and fungal pathogens into cotton bolls. Current Microbiology. 59:405-412.

Interpretive Summary: The southern green stink bug (SGSB) is one of the most important pests of cotton due to changes in insecticide application programs. Previously, we demonstrated that boll damage associated with SGSB feeding is actually dependent on whether the insects harbor and deposit an infective bacterium called Pantoea agglomerans. If stink bugs that are free of cotton pathogens feed on developing bolls, then seed and lint is not noticeably affected. Conversely, effects of feeding by stink bugs that carry and transmit the P. agglomerans disease agent results in spoiled, unmarketable lint and seed. Notably, we also determined that developing cotton bolls become immune to both insect damage and P. agglomerans infections at three weeks after flower fertilization. In this study, we examined the potential of the SGSB to act as a conduit of two other bacterial cotton pathogens (P. ananatis and Klebsiella pnuemoniae) as well as a pathogenic fungus (Nematospora coryli). Here, we showed that the stink bugs could acquire each of the three tested pathogens from a contaminated food source. However, pathogen-infested insects were capable of transmitting only the N. coryli into green bolls; as a result, these bolls infected by the fungus were the only ones that showed disease. Collectively, this research can benefit producers by optimizing a pest protection program to avoid costly and unnecessary insecticide applications.

Technical Abstract: Recently, we described the vectoring of an opportunistic Pantoea agglomerans strain into green cotton bolls by the southern green stink bug (Nezara viridula L.) (SGSB) that resulted in disease. We hypothesized that our established experimental disease model could be used to determine whether SGSB simply provide a general transmission mechanism. Our hypothesis was tested using two opportunistic bacterial pathogens of bolls (P. ananatis and Klebsiella pneumoniae) and the known yeast pathogen Nematospora coryli. Variants of P. ananatis (strain Pa-1R) and K. pneumoniae (strain Kp 5-1R) selected for rifampicin (Rif) resistance were used to track bacterial movement during feeding. Nematospora coryli was detected only from laboratory-reared SGSB directly exposed to the fungus. Both Pa-1R and Kp 5-1R were recovered from SGSB provided a contaminated food source and caged on bolls for two days at levels reaching 10**3 and 10**4 colony forming units (CFUs) per insect, respectively. However, bolls caged with insects infested with Pa-1R or Kp 5-1R and with evidence of feeding did not become diseased nor was either opportunists detected from boll tissues. Insects infested with N. coryli transmitted the pathogen which resulted in diseased bolls and yeast concentrations reached 10**6 CFUs/g locule tissue two weeks following the caging period. Notably, each of the three pathogens independently caused boll disease if directly inoculated using a needle puncture that simulated stink bug transmission. Overall, SGSB vectoring of a cotton pathogen was not soley based on microbe acquisition, indicating that colonization of the pathogen in the insect mouthparts or salivary glands is necessary for transmission.