Fungicide resistance in Botrytis cinerea has caused increased concerns
about losses due to gray mold on many important agricultural and hort
icultural crops. Since bicarbonates have been reported to be an effect
ive control of powdery mildew on greenhouse roses, the purpose of this
research was to determine the effectiveness of bicarbonates against B
. cinerea. Assessments were made of in vitro fungal colony growth in r
esponse to ammonium, potassium, and sodium bicarbonates. Bicarbonates
inhibited colony growth at concentrations as low as 20 mM. In addition
, comparisons of several ammonium, potassium, and sodium salts were co
nducted to determine whether cation or anion is the active moiety. Alt
hough the bicarbonate anion primarily affected growth, the ammonium ca
tion also contributed greatly to fungal growth inhibition. With the ex
ception of dibasic phosphate, only salts with high pK(a), values or th
at are reducing agents, or both, decreased colony growth. The effect o
f pH on B. cinerea was then examined. Since bicarbonate anion concentr
ation is related to pH, this parameter was examined in combination wit
h several salts to separate pH effects from bicarbonate effects. As pH
increased from 7.0 to 8.5, colony growth decreased with bicarbonates
and phosphates, but not with ammonium sulfate. Since bicarbonates and
phosphates decreased colony growth more than could be accounted for fr
om pH alone, and since both have buffering characteristics, buffering
capacity was examined and found to decrease colony growth but not as m
uch as bicarbonate. Therefore, bicarbonates control B. cinerea colony
growth in vitro, and both pH and buffering capacity contribute to, but
are not solely responsible for, growth inhibition.