| Disease (causal agent) |
Symptoms |
Survival of pathogen and effect of environment |
Comments on control |
Armillaria root rot
(Armillaria mellea) |
Symptoms are similar to crown rot but distribution in
the field is different. Examination of affected plants reveals white
fungus plaques beneath the bark at or below soil line on main stem.
Erica canaliculata and E. hirtiflora have been infected. |
Fungus survives for long periods in infected roots buried
in soil. Infection is favored by the same conditions that are favorable
for plant growth. |
Avoid fields just cleared of oaks or other susceptible
woody plants. This is not a common disease of heather. |
Chlorosis
(Iron deficiency) |
Foliage turns yellow and some turns almost white, especially
new growth. Terminal growth may die and plants are stunted. Occurs
if soil pH is too high. |
Soils that are too basic as a result of too much calcium. |
Spray plants with ferrous sulfate using 6 to 8 pounds/100
gal water. Thoroughly wet the plants using 100 to 150 gal/acre. Apply
once a month starting in early spring as growth commences. If stems
turn black, reduce dosage and frequency of treatment. Acidify soil. |
Powdery mildew
(Erysiphe polygoni) |
Shoot tips are reddened, then yellow and turn brown
and fall off. A side bud develops into the new terminal and successive
killing of the tips causes crooked, twisted growth. The white powdery
mildew growth is often difficult to find. Affected plants are stunted
and bushy. Erica persoluta is damaged. |
On living heather foliage. Fungus is favored by moderate
temperatures, partial shade, and dry foliage. |
Several fungicides are available to protect foliage
from infection. Start applications in spring and after each irrigation.
During very hot periods, sulfur may damage foliage and flowers; avoid
excessive rates of application. more info |
Root and crown rot
(Pythium spp., Phytophthora cinnamomi) |
Plants are stunted or may suddenly wilt and collapse.
Roots are killed and the base of the stem (crown) is attacked, causing
a complete or partial girdling. Erica hirtiflora (= E. regerminans)
and E. hyemalis are very susceptible. Erica canaliculata
(E. melanthera) is moderately resistant and E. persoluta
is resistant. |
Soilborne fungus with wide host range. Fungus also survives
in infected plants. Favored by excessive soil moisture, poor drainage,
and warm temperatures. |
Avoid introduction into new areas by growing or obtaining
disease-free plants. Take cuttings from high on the plant and use
heat-treated or fumigated propagative and growing medium. Prevent
infection in the nursery by periodic treatments with mefenoxam. Careful
water management will provide some relief in field plantings. Mefenoxam
applied as a drench also helps. more info:
Pythium Root Rot,
Phytophthora Root and Crown Rots
|
Rust
(Uredo ericae) |
Small pustules of powdery orange spores occur on leaves.
Infected leaves usually turn yellow and abscise. Erica hirtiflora
and E. persoluta var. alba are infected. |
On foliage. Spores are airborne and may be carried by
the wind for many miles. Pathogen is favored by moderately low temperature
and dew or rain. |
Protect foliage with sulfur applied as a dust or spray.
Start applications in late March and continue at 10- to 14-day intervals
until rains stop. During very hot periods sulfur may cause damage
to foliage and flowers; avoid excessive rates of application. Also
avoid overhead watering. more info |
Verticillium wilt
(Verticillium dahliae) |
Wilting, yellowing, and defoliation occur frequently
on only one side of the plant. Examination of crown and roots, which
appear healthy, helps differentiate this disease from root and crown
rot. Symptoms usually first appear in early summer. Erica australis
and E. persoluta are affected. |
Fungus is soilborne and has a wide host range. Fungus
invades plant in the cool spring plugging the water-conducting tissues.
Symptoms occur when plant is stressed for water, particularly during
warm periods. |
Avoid fields that have been in susceptible crops or
weeds such as tomato, chrysanthemum, strawflowers, nightshade, and
others. Propagate plants, using heat or chemically-treated medium.
The fungus can be eliminated from field soil by fumigation with methyl
bromide-chloropicrin mixture. more info |
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