|
Necrosis on iris foliage
due to leaf spot
(Photo by Jay W. Pscheidt, 1999, An Online
Guide to Plant Disease Control,
Oregon State University Extension Service)
With proper planting and minimal maintenance,
bearded irises are rather carefree when compared to many other garden
plants. However, some diseases and pests do attack irises (especially with
the high heat and humidity we have here in the South), leading to decline or
even death of the plant. These threats must either be prevented or
destroyed to have a healthy garden.
Why Does an
Iris Fail to Thrive?
When an iris fails to thrive,
gardeners are left searching for reasons. The following conditions are
frequently present when weak growth, poor bloom or decline is noticed. If your
irises are not performing the way you believe they should, one of these
"top ten reasons" may be the cause:
1.
Leaf damage from virus, fungi, bacteria, insects or animals
2.
Rhizome damage due to borers, excessive moisture or bacteria
3.
Competition from closely grown seedlings
4.
Misuse or buildup of herbicides or insecticides
5.
Root damage from careless hoeing or tilling
6.
Poor nutrition causing weak plants (trace minerals, humus,
nitrogen, potassium, phosphorus, and lime)
7.
Acid rather than neutral to slightly alkaline soil PH
8.
Roots of trees or plants interfering with the iris' growth
9.
Weather conditions that are too dry, too hot (leading to crown
rot) or too wet
(causing soil compaction, poor oxygenation, and water borne diseases)
10. Any combination of the
above
All of these conditions place the iris under
stress. Minor stress can be beneficial, such as when careful cultivation
encourages new growth. However, if the stress is severe relative to the
condition of the iris, the iris is more susceptible to the onset of
disease. Fortunately, when your iris has succumbed to attack, either by
pests or disease, there are strategies available to help bring your iris
back to health. Below is a list of the most common problems. Click on the
photos to see a brief discussion on recognizing and troubleshooting each
one.
|
DISEASES
|
|
Blight (Southern) /
Crown Rot
|
|
Botrytis
|
|
Leaf Spot (fungal and
bacterial)
|
|
Mosaic (Iris)
|
|
Rhizome Rot (bacterial
and Sclerotium)
|
|
Rust
|
|
Scorch
|
|
PESTS
|
|
Aphids
|
|
Beetles (Hoplia and
Carrot)
|
|
Borers (Iris)
|
|
Budflies / Bud Worms
|
|
Caterpillars
(Omnivorous Looper and others)
|
|
Critters (squirrels,
opossum, raccoons, rabbits, rats and mice)
|
|
Mites (Spider)
|
|
Nematodes (Root Knot)
|
|
Slugs and Snails
|
|
Thrips
|
|
Whiteflies
|
|
