Ka. Holmes et al., FACTORS AFFECTING THE CONTROL OF PYTHIUM-ULTIMUM DAMPING-OFF OF SUGAR-BEET BY PYTHIUM-OLIGANDRUM, Plant Pathology, 47(4), 1998, pp. 516-522
Application of Pythium oligandrum to a soil-based compost as a mycelia
l suspension (5 x 10(2) CFU g(-1) of dry compost) and oospore alginate
pellets (10(5) oospores/g of dry compost) controlled pre- and posteme
rgence damping-off of sugar beet caused by Pythium ultimum to a level
similar to metalaxyl seed treatment. Oospore seed treatments and aqueo
us suspensions of oospores applied to compost failed to control diseas
e. Problems in the use of P. oligandrum oospore inocula for the contro
l of damping-off were highlighted. It was shown that treatment of oosp
ores with cellulase (20 g L-1) increased germination approximately thr
ee-fold in comparison to untreated spores. Untreated and cellulase pre
treated oospores were subsequently evaluated as seed treatments for th
eir ability to control damping-off of sugar beet. The highest rate of
pretreated oospores (10(4) oospores/seed) gave levels of emergence and
establishment in infested compost that were not significantly differe
nt from the uninfested controls, whereas seed treatment with untreated
oospores gave no significant reduction in disease. In a trial carried
out in a controlled environment to assess the effect of pH (4.5-8.0),
P. oligandrum (10(4) cellulase pretreated oospores/seed) was shown to
control pre- and postemergence damping-off of sugar beet at pH 7.0 an
d 7.5 only.