Agriculture Reference
In-Depth Information
growth on the fruit. Since these symptoms appear late in the season, treatment and preven-
tion early on is important. The fungus can also infect berries through wounds, such as from
birds.
CONTROL
You can best control bunch rot through an integrated approach that includes spraying,
mechanical means (including canopy management), and sanitation and irrigation tech-
niques.
Practice good canopy management to increase exposure of the grape clusters to air
and sunlight, just as with powdery mildew. From early summer to late summer, pull leaves
and shoots to expose 70 to 80 percent of the fruit. Avoid overhead irrigation, as moisture on
the vines creates an environment that allows bunch rot to occur. Encourage air circulation
and keep the vines dry.
Bunch rot, or botrytis, can appear late in the season and attack grapes just as
they are ripening.
A regular program of preventive spraying with fungicides such as organic Stylet-Oil
can help control bunch rot. While several methods of spray control have been suggested,
studies show that spraying when environmental conditions are conducive to the growth of
the fungus (during times of wetness or higher humidity in the vineyard) seem most suc-
cessful. Just as with powdery mildew, begin your spray after bud burst and continue every
two weeks through the damp or rainy part of the season, until veraison. Do not spray after
