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Daylily rust (Figure 1) is caused by the
fungus Puccinia hemerocallidis. It was a new
disease to the United States, but now has
been found in many states. In recent years,
it has been found frequently in the western
states. In 2005, a total of eleven nurseries
were found to have rust infected daylily
plants. Currently, the state does not
quarantine the disease, but enforces the
state law to ensure nursery stocks in the
state free of this harmful disease. If an
incidence of daylily rust is found in the
nursery, the following procedures should
apply.
 |
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Figure 1:
Typical yellow spots on leaves by naked eyes
(left picture) and orange,
tiny round urediospores observed on the
undersurface of leaves with a dissect
microscope (right picture). |
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1. |
If daylily rust
is suspected or noticed by nursery staff or
our inspectors, entire group of daylily
plants in the nursery should be stopped for
selling. A representative samples will be
collected by a NDOA nursery inspector. |
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2. |
The NDOA plant pathology laboratory will
examine the sample and confirm the presence
or absence of the fungus Puccinia
hemerocallidis in the sample. This is
usually done in the same day. |
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3. |
If samples are confirmed to be negative of
daylily rust infection, the plants on hold
will be released by a NDOA nursery
inspector. |
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4. |
If a positive daylily rust infection is
confirmed, the entire group of daylily
plants will continue to be on hold until the
following requirements set in either option
are met: |
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Option 1: Chemical treatment and
sanitation |
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1. |
Carefully remove all infected foliage
including those with even tiny necrotic
lesion or discoloration on leaves. These
symptoms are considered to be the case of
early infection. |
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2. |
Apply Banner Maxx (systemic) or Heritage
(systemic). Other fungicides such as
Systhane, Strike and Banner Maxx (all
systemic), Daconil (protectant/contact),
Dithane (protectant/contact), or Contrast
(systemic) are also applicable. The only
requirement is to use at least one systemic
fungicide in the treatment. |
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3. |
To increase effectiveness and avoid
resistance, nurseries can rotate fungicides
from following two category fungicides. |
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Category 1 |
Category 2 |
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Propiconazole (Banner MAXX |
Chlorothalonil (Comcorde SST,
Daconil Ultrex, Echo 90, Pathguard,
Spectro 90) |
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Azoxystrobin (Heritage) |
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Flutolanil (Contrast) |
Mancozeb (Dithane, Fore,
Manzate, Pentathlon) |
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Myclobutanil (Systhane) |
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4. |
Formerly infected group of plants treated
with above procedures that re-grow
asymptomatic foliage (6-10’’ leaves) are
eligible for sale after re-inspection by a
NDOA nursery inspector. |
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Option 2: Destruction of limited number
of susceptible plants voluntarily |
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The nursery may choose to safely destroy all
visibly infected plants rather than try to
re-grow asymptomatic foliage. This option
may become more demandable if certain
extremely susceptible varieties are
infected. Elimination of those plants will
protect less susceptible varieties from high
inoculum pressure and subsequent disease
development. |
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If there is any concern on
daylily rust disease in your nursery or on
this enforcement procedure, please contact
the Nevada Department of Agriculture @
775-688-1180. |
