DEPARTMENT OF AGRICULTURE


controlled. Uncontrolled early outbreaks are a good source of
infection for other nearby plant beds.

 Blue mold is readily controlled in plant beds by dusting or
spraying, and several materials are effective. Ferbam and
zineb are recommended, and the most commonly used at present.
Ferbam and zineb are used as preventive fungicides and give
protection only if the plants are kept dusted with the materials
so that blue mold is not permitted to get a start. Sodium or
potassium nitrate will not control blue mold. These materials
serve only as an aid in the recovery of blue mold-injured
plants.

 Ferbam and Zineb Treatments: Ferbam and zineb are pow-
dered materials that may be used very satisfactorily as either
dusts or sprays and give excellent control of blue mold. Com-
mercially prepared dusts are most commonly used, but they
may be prepared by the grower as follows: 15% ferbam dust-
mix at the rate of approximately 20 pounds of fermate to
80 pounds of talc, pyrax or Fullers' earth. If a smaller quantity
is desired reduce to 1 pound of fermate to four pounds of
filler. 6.5% zineb-add nine pounds of filler to each one
pound of 6.5% concentrate.

 These materials should not be used in the concentrated form.
The above concentrations of dusts will give excellent control
of blue mold. The fungicide should be applied twice a week-
always water and then dust-dust as quickly as possible after
rains and put the dust on instead of putting it off. Use ferbam
dusts at the rate of 11/2 to 2 pounds per 100 square yards of
bed, or zineb dusts at 1 to 11/2 pounds when the plants are
about the size of a dime or when blue mold is known to be
in the vicinity. As the plants grow increase the quantity pro-
gressively up to a maximum of 3 to 4 pounds per 100 square
yards per application when the plants are large enough to
transplant. It is best to apply the dust when the plants are
wet (after watering, rain or dew) and when there is the
least wind. Fifty pounds of a 10 or 15% dust should be ade-
quate to treat 100 square yards for one season, even with
severe blue mold conditions. Ten or more applications may be
necessary during a season. Continue dusting until the plants
have been transplanted.