Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2016
Publication Date: 7/6/2016
Citation: Medrano, E.G., Bell, A.A., Duke, S.E. 2016. Cotton (Gossypium hirsutum L.) boll rotting bacteria vectored by the brown stink bug, Euschistus servus (Say) (Hemiptera: Pentatomidea). Journal of Applied Microbiology. 121:757-766.

Interpretive Summary: Cotton bolls can develop rot without exhibiting external symptoms. Several pathogens, predominately bacterial, are responsible for the disease which results in economic losses that impact producers. We report that the brown stink bug can vector a bacterial cotton pathogen into green bolls. The brown stink bug is a recognized and significant pest of cotton that is difficult to control by pesticide application. Interestingly, bolls fed upon by piercing/sucking insects that do not carry a boll rotting agent tolerate the trauma. This work is an important step to understand this interior boll rot phenomenon to develop an effective a pesticide application regime to control this disease.

Technical Abstract: Determine the capacity of the brown stink bug (Euschistus servus) to transmit an infective Pantoea agglomerans into cotton (Gossypium hirsutum, L.) bolls. A laboratory colony of the brown stink bug (BSB) was maintained on fresh green beans. The P. agglomerans mutant strain Sc 1-R that holds rifampicin (Rif) resistance was utilized as the opportunistic cotton pathogen. Treatment green beans were sterilized, soaked in either sterile water or in a suspension of strain Sc 1-R and offered to adult insects. Following exposure to treated green beans, the insects were caged with unopened greenhouse-grown cotton bolls (one insect/boll). After two days, live BSB were collected, surfaced sterilized, ground, serially diluted, and then plated on non-selective media and media amended with Rif. Feeding was based on boll wall puncture evidence, and was recorded two weeks after exposure to insects. Seed and lint tissue were harvested, ground, serially diluted, and then plated on media with and without Rif. Microbes were recovered on non-selective media from all BSBs processed, and from seed and lint with signs of BSB feeding at concentrations ranging from 102 to 109 CFU g-1 tissue. Rifampicin resistant bacteria were recovered strictly from insects exposed to strain Sc1-R and from seed and lint of respective bolls with inner boll puncture wounds. Only 20% of bolls with apparent evidence of insect feeding on the outer boll had corresponding punctures in the inner wall of the carpel. Conversely, bacteria were recovered from all of the bolls with feeding evidence on the interior wall including those with bacterial infections of seed and lint. Euschistus servus was capable of both acquiring and transmitting the opportunistic P. agglomerans strain Sc 1-R into developing, unopened cotton bolls. Infections by the transmitted Sc 1-R strain resulted in tissue deterioration of the entire locule that occasionally concealed insect feeding of the internal carpel wall. Insects not exposed to the pathogen deposited bacteria yet, the microbes were detected only about the area surrounding the point of penetration (c. 3 mm) and produced insignificant damage to the locule. This is the first study that concretely showed the capacity of the BSB to transmit plant pathogenic bacteria resulting in boll disease.