Optimara Growing Tips
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a plant is affected by the Phytophthora fungus, it is lost and should be removed from the
table.The fungus spreads very easily in a crop that is too moist in combination with excessive
greenhouse temperatures.
You should take preventive action against Phytophthora. A reliable method is to drench the
African Violets with an Aliette-Benlate combination (125 combined with 50 parts per mil or 1oz.
Aliette combined with 1/2 oz. Benlate to 6 gallons) right after potting. Spraying Banol, or the
combination of both Banol and Benlate, is another good preventive step. A third possibility is to
blend Ridomil MZ into the potting mix.
• Powdery Mildew --
During spring and fall, African Violets are likely to become infested
with powdery mildew if the outside temperatures are low and there are cool drafts in the
greenhouses during ventilation. One can recognize grayish-white, powderlike spots on the
blooms as well as on the leaf surfaces. As a preventive method, we recommend to use sulfur
burners. You should let the sulfur burners run for 90 minutes every night at about midnight. You
will need about 5 burners per 10,000 sq.ft. of greenhouse space.
Another very effective treatment against powdery mildew is to spray with Pipron or Nimrod. Spray
the solution under high pressure high into the greenhouses so that it is spread evenly over the
plants. The plants should not be sprayed dripping wet, i.e., spray about 5 gallons per 10,000
sq.ft. greenhouse space. Be careful with Nimrod, African Violets that are in bloom should not be
sprayed with this chemical since it can cause severe damage to the flowers.
• Botrytis --
Botrytis is a grayish green mold which first appears on the blooms and on the
leaves. At a later stage, the blooms and leaves start rotting. As a preventive measure, we
recommend to install air circulating fans within the greenhouse. The fans keep the air flowing and
help reduce botrytis. The right humidity lies between 60-75%. In cases of 95% humidity and
above, it is recommended to slightly increase the greenhouse temperatures and to open the air
vents or air fans in order to lower the high humidity rate.
Another effective preventive measure during humid summer months is the spraying of Ornaline.
You should apply Ornaline once a week over your flowering crop to kill any potential development
of Botrytis. We also recommend to spray the plants one day before they are boxed up and
shipped, thus, preventing Botrytis during distribution. You can also experiment with Benlate
against an infestation by botrytis. However, you have to count with some residue and spray spots
on the blooms.
• Rhizoctonia --
You can recognize a Rhizoctonia infestation by the black rot around the
base of the plant. When the plant is severely infested, it is lost. You should immediately remove
the infested plant to prevent further spreading.
Treat Rhizoctonia by drenching the infested African Violets with Benlate.
