Agrobacterium Bronzing and Wilt of Cotton: Epidemiology and Control
Feb 15, 2019

Crop Protection WCRC WCRC2

Bronzing and sudden wilt syndrome that develops in USA cotton plants during boll development in hot weather have been associated with infections of roots by Agrobacterium biovar 1 strains. Conditions favouring the multiplication of the bacteria in roots and development of symptoms include: high clay content in soil, high soil temperatures (above 30oC), excess nitrogen and/or irrigation and deficiencies of phosphorus, sulphur and/or potassium. Certain isolates of Fusarium species, Talaromyces flavus, Pseudomonas aeruginosa, Burkholderia cepacia and Bacillus subtilus were antagonistic to Agrobacterium and alleviated symptom development when added to pasteurized soils before planting Agrobacterium infested seed. Increasing the amounts of phosphorous and sulphur in the fertilizers decreased bacterial multiplication in roots as well as bronzing and sudden wilt symptoms. Cultivar resistance was evaluated by incubating seed in germinating towels wet with bacterial suspension for 24 hours at 30oC, planting in pasteurized soil containing 15.0-2.5-25.0 fertilizer containing chelated minor elements. Generally short-season cultivars that fruited early were more susceptible than cultivars that fruited at higher nodes and were heat tolerant. Some short season cultivars were more resistant than others.

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