The base of my aster is yellow and brown...?
Question:I have a 3 year old aster that looks gorgeous until you look at the base. It is yellow and brown and looks like it is rotting. Does anyone know what this is and how I can treat it? Thanks!
Answers:
The first answer may be close to your problem. Over watering or under watering can cause yellowing of the leaves. At least it's a good start. Try backing off the watering.
As far as diseases go, asters are not prone to a lot of diseases. Aster yellows can turn leaves yellow, but aster yellows start on the newer/younger leaves, not the oldest leaves at the base of the plant.
Aster wilt can start at the base of a plant and affect the stem too, but aster wilt causes stunting. I did not hear that your plants where stunted. Aster wilt will cause the lower leaves to yellow and eventually turn browm. There is no effective control for aster wilt. Remove infected plants from your healthy plants.
Lacebugs are a ridiculous suggestion considering its at the base of the plant. Bug damage tends to be random on a plant and lacebugs suck sap, so you would have yellow spots.
Powdery mildew is a white powder on the upper side of the leaves. I don't remember this in the problem description!
Rust produces orange/red spots on the leaves with dark margins. Didn't see that in the description either.
Rhizoctonia blight is not common in asters. It usually results in stem cankers. It's a soil borne disease and spraying leaves with milk, of baking soda, or any other home brew concoction is not going to do a thing for your asters.
Milk as a fungicide works for certain fungal diseases. It is well documented that milk can help prevent powdery mildew and black spot on roses. Baking soda has also been reported as effective on powdery mildew. What these two antifungal prescriptions have to do with an aster disease is beyond me! Prescribing a cure when you have not identified the disease is a waste of time and not good practice.
Yellow and brown is always an indicator of too much watering. Let it dry out for a bit before you water again. It will green up.
Several factors can cause the leaves of Asters to turn yellow & then turn brown.
Sometimes the lacebug sucks the plant juices from the undersides of leaves. "Leaves turn yellowish and eventually brown and fall off."
http://www.uvm.edu/pss/ppp/articles/aste...
It's more likely that dampness & humidity caused the yellowing & browning that you described. Asters like full sun & good air circulation.They like soil with good organic content kept evenly moist, and prefer that their roots be kept cool. If your plants are in clay soil, add some compost & lime to improve drainage.
In general, it's not unusual for older leaves to turn yellow and fall off when new leaves appear or when most of the energy of the plant is put into flowering.
Since this is common & the tall Asters can look lanky, it's a good idea to place plants like Mums in front of them to help cover up this flaw.
Good luck! Hope this helps.
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