Technical Abstract: Bronzing and copper top symptoms associated with infection of cotton roots by Agrobacterium biovar 1 isolates were enhanced by low availability of sulfur and/or potassium. Sudden wilt and interveinal leaf necrosis symptoms were enhanced by low availability of phosphorous. The nitrogen level relative to the phosphorous level was critical for bacterial multiplication in roots. Progressive increases in the N/P ratio above 2 i the fertilizer caused progressive increases in Agrobacterium concentrations in roots and in disease severity. These increases in disease severity were greatest when phosphate was marginal or low in soil, but also occurred when soil tests showed adequate phosphate. When cotton cultivars were inoculated with Agrobacterium and grown in a pasteurized soil with 25 percent clay, none were able to set and carry fruit if nitrogen alone, as recommended by a soils laboratory, was used as the fertilizer. Greater amounts of phosphorus and sulfur may be needed in fertilizers when sudden wilt and bronzing are a problem.