Introduction of an opportunistic bacterial cotton pathogen into

bolls by the southern green stink bug (Nezara viridula L.)

E. G. Medrano, J. F. Esquivel, and A. A. BellUSDA-ARS-SPARC, College Station, TX

Seed Rot of South Carolina Cotton

• Emerging disease

• First reported during 1999 in South Carolina

• Yield losses from 10 to 15%

• Spread to fields located throughout southeastern Cotton Belt states

Disease Symptoms

• Disease symptoms manifested inside bolls

• Exterior carpel of immature diseased bolls are non-symptomatic

• Cross-sections of immature diseased bolls reveal necrotic seed and discolored fiber

Previous Work

• Role of Pantoea agglomerans in opportunistic bacterial seed and boll rot of cotton (Gossypium hirsutum) grown in the field (Medrano and Bell,

2007, Journal of Applied Microbiology- 102, 134-143)• Transmission of cotton seed and boll rotting

bacteria by the southern green stink bug, Nezara viridula L. (Heteroptera: Pentatomidae) (Medrano, Esquivel, and Bell, 2007, Journal of

Applied Microbiology- in press)

Boll inoculated with P. agglomerans Rif (PaRif )*

*28-gauge needle simulating insect puncture (Medrano & Bell 2007)

r r

Comparison of diseased greenhouse* and field cotton

*28-gauge needle simulating insect puncture (Medrano & Bell 2007)

Cotton Insect Pests• Piercing/sucking mouthparts used for feeding

on developing fruit

• Includes stink bugs, lygus, and cotton fleahoppers

Insect Transmission Study Method• Lab-reared southern green stink bugs (SGSB) were raised on

fresh green beans (not sterile) that were replenished every 2 days.

• Bacterial exposure to insects:

SterilizedGreenBean

PaRif r

H2O

Provided to insectfor 2 days

Soaked 2 min in:

or

Insect Transmission Study Method (cont’d)

• Cotton boll harvesting: -Evidence of insect feeding was determined after

boll exposure to insects. -Bolls were surface sterilized and then seed and lint

tissue were aseptically collected, triturated, and thendilution plated on media with/without Rif.

• Exposure of cotton bolls to insects:

Weeks PostAnthesis:

2 wks Caged2 days

Harvestedafter:

2 wks

Cotton bolls exposed to SGSB

PaRif +r

PaRif -r

Cotton bolls exposed to SGSB

PaRif +r

PaRif -r

Cotton bolls exposed to SGSB

PaRif +r PaRif -r

Cotton bolls exposed to SGSB

PaRif +r

PaRif -r