The effects of oxygen deprivation or poor drainage and Pythium root ro
t on development of red rot, caused by Colletotrichum falcatum, and sp
ring shoot population of sugarcane were evaluated under controlled and
field conditions. Detached stalks of five cultivars were exposed to l
ow atmospheric oxygen (0.5 to 2.7%), created by enclosing stalks in se
aled chambers through which humidified nitrogen gas was passed for 0,
1, or 2 weeks. Stalks were then inoculated with C. falcatum and mainta
ined for 6 weeks with humidified air flow. Red rot severity, assessed
as four disease traits, was not increased by previous oxygen deprivati
on. In field experiments, inoculation of stalks of three cultivars wit
h C. falcatum before planting resulted in a reduction in shoot populat
ions the following spring. Poor drainage resulted in an additional red
uction in shoot populations developing from inoculated stalks. Soil at
mospheric oxygen was reduced in the root zone below planted stalks und
er poor drainage conditions. However, only minor reductions in oxygen
were detected in the zone of elevated rows in which planted stalks wer
e located. The detrimental effect of poor drainage on shoot population
s from inoculated stalks was alleviated by metalaxyl application. Pyth
ium root rot, caused by Pythium arrhenomanes, reduced the initial root
system and growth of shoots in greenhouse experiments. The combinatio
n of P. arrhenomanes and C. falcatum inoculation increased dead bud pe
rcentage in one of two cultivars and red rot severity for both. The re
sults suggest that spring shoot populations developing from red rot-af
fected stalks exposed to poor drainage can be reduced by the combined
effects of red rot and Pythium root rot.