Hi Gang,
Stagonospora can be a nasty pathogen of some bulbs (e.g., Narcissus
hybrids) where is destroys foliage in the leaf scorch stage. In amaryllids
Stagonospora can cause leaf spots and the familiar ugly red blotch on leaves
and bulbs.
Stagonospora is the only recurrent fungal problem I have in the bulbs
that I grow and I control it with twice yearly applications of myclobutanil
(a.k.a., ziram). Myclobutanil does not cure the problem for me (at least
not when applied only twice a year), but it sure controls the problem. I
use myclobutanil because it is a systemic fungicide and because I understand
it to be of moderate or low toxicity for mammals, birds, and fish.
Additionally, it does break down in time in soil or water.
Of course, I take care to remove infested debris, and cut off leaves
that are showing symptoms (especially Crinum). Debris removal is always a
part of my fungal control efforts.
I use a Spectracide product called Immunox that contains myclobutanil.
The Spectracide products come in liquid of dry forms. All new plants coming
into my garden (even cacti and germinating seeds, etc.) are treated with an
overnight dip in a myclobutanil solution.
For potted plants, I sprinkle about 1 tablespoon of dry powder (the lawn
granules) on top of the soil of a gallon container. I scale up accordingly
for larger containers. Large bulbs in the ground (e.g., a big Crinum) get
about 6-8 ounces (about a cup) of the granules sprinkled over the soil
around the plant. I apply the granules in fall and spring. The fungus is
controlled and I've learned to accept minor blemishes and spots.
There is a catch with fungicides along the Gulf Coast: some plants
(including many Cape bulbs) are going to die from fungal disease unless they
are protected from too much rain and humidity. Thus, I don't expect
fungicides to perform miracles.
As always, I encourage anyone using a pesticide to read up about it and
make informed decisions. And all garden chemicals need to be stored away
from pets and children.
Cordially,
Joe
Conroe TX
LINK: Fungal diseases of Narcissus
http://tinyurl.com/vvo5d/
LINK: Narcissus leaf scorch
http://tinyurl.com/y4umjs/
LINK: ExToxNet Info about myclobutanil (ziram)
http://extoxnet.orst.edu/pips/ziram.htm