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What is it?
This disease organism which became widespread in Ohio in 2012 grows
under the leaves and on the stems of impatiens which eventually cause
severe leaf drop and death of its host plant.
What other
plants are affected?
While other plants can be infected,
they seem to tolerate downy mildew and some are even able to thrive
despite of it. Only Impatiens walleriana (the impatiens in flats) are
infected. New Guinea and Sunpatiens are
NOT
affected.
What are some
shade substitutes for Impatiens?
Caladiums, Coleus, Salvia (in the
bloom stage) Begonia, Torenia, some Vincas, Sunpatiens, New Guinea
Impatiens, the new Sun Harmony New Guinea Impatiens, Calliope Geraniums
and Browallia.
Aren’t some of
these substitutes more expensive than using flats of Impatiens?
They are, as many have to be grown
from cuttings instead of seed like the impatiens in flats; however, some
of the substitutes like wax begonia and torenia are in the inexpensive
flats and the other substitutes like
Calliope geraniums and Sun Harmony Impatiens can be planted much farther
apart so that you plant roughly one-fourth (Ľ) the number of plants you
would normally have planted and with less labor.
What if I plant
Impatiens in pots, will they be affected?
Probably, as the downy mildew
spores are spread not only by splashing water but spread over long
distances by wind.
 So
if I still want to plant impatiens from flats, what do I need to do?
We have a product called
Agri-fos
that is a systemic fungicide effective in
controlling the disease on impatiens. Apply it as a spray to the
foliage and stems at the following rate: 1 fluid ounce (or 2
tablespoons) per 1 gallon of water. Apply it to the plants with a pump
sprayer or an Ortho Dial-n-Spray. If you use the Ortho Dial-n-Spray,
just dial it to the 1 fluid ounce per gallon rate and spray accordingly.
If you have a smaller area than 100 square feet, it is best to use a
pump sprayer. Just reduce the amount of water and product
proportionally. Do read the product label!
Note: You must spray the plants the same day you plant them and repeat
the treatment every 14-21 days. Thorough coverage of the leaves and
stems is essential. Downy mildew must be prevented as once the plants
get the disease it’s too late to treat them. One gallon of solution will
cover 100 square feet on young plants. Do not apply more spray solution
than 1 gallon per 100 ft˛.
Is Agri-fos very
toxic to me, my family, pets and pollinators?
No, it is just a form of phosphorus
acid and is relatively safe compared to other fungicides. Just wear
rubber gloves as with any chemical when you apply it. After the foliage
is dry from the spray, Agri-fos is harmless.
Is Agri-fos
expensive?
It costs roughly $1.00 to cover 100
square feet for each time you spray. It works great for other diseases
on many plants through its’ systemic action. See label for more
information
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