Interaction between age of maize plants, environmental factors, and inoculum strength of Erwinia carotovora var. chrysanthemi on the extent of stalk rot incidence.

For optimum disease incidence and maximum mortality of maize plants, due to Erwinia carotovora var. chrysanthemi (Burkholder et al.) Dye, a temperature of 35 degrees C accompanied with 70 per cent humidity and inoculum potency of 2 x 10(8) cells/ml were essential for younger plants of 15 and 30 days of age. On the other hand, 45- and 60-day-old plants, due to acquisition of a certain degree of maturity, although responding and showing maximum disease symptoms at the same temperature of 35 degrees C, required a higher humidity of 90 per cent. A heavy dose of 4 x 10(8) cells/ml was needed for effectual disease response for 45- and 60-day-old and mature plants.