JANUARY
2005
By
Beverly Shaw
Advanced
Master Gardener
Purdue University
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Q. I have a pink lemonade honeysuckle vine. It has bloomed all summer,
but the leaves are turning a powdery white and falling off. Is there a
remedy to save my plant? -- Sylvia R. Kline, Ferdinand, Ind.
A. Powdery mildew is the name for the grayish-white powdery coating caused
by a fungus growing on plant leaves, shoots and flowers. This disease
is caused by a group of similar fungi that attacks a wide variety of plants,
including lilac, beebalm and honeysuckle.
Although plants infected with powdery mildew rarely die, the disease can
reduce the attractiveness of landscape ornamentals.
Conditions, including high humidity, overcast weather, warm days and cool
nights favor powdery mildew development. The disease is common in crowded
plantings and in areas with restricted air movement. Recommendations to
reduce infection include adequate spacing between plants and choosing
the right plant for the right location so as to make conditions less favorable
for the disease.
There is no cure for infected plants, however, preventative fungicide
sprays will help protect healthy plant tissue from infection. Products
containing active ingredients, such as chlorothalonil, triforine and sulfur,
are labeled for control of powdery mildew. Hosts and diseases listed on
specific product labels may differ between products containing the same
active ingredient, thus be sure to read the label.
At the end of the growing season, remove powdery mildew-infected leaves
from the ground to reduce carryover of the mildew fungi into the next
season.
Q. I have been fighting sandburs in my back yard for 20 years. Someone
told me to put lime on them, but this didn’t work. I have been pulling
them out, but there are too many! What can I put on them to get rid of
them for good? -- Linda Williams, Wheatfield, Ind.
A. Sandbur is a common weed in northern Indiana on very sandy soils. Most
people don't realize they have sandbur in their lawn until they or their
children step on one with bare feet. Sandbur is an annual grassy weed
that germinates in the spring, forms the spiny burs during the summer
and then dies with the frost in fall. If you had sandbur in your lawn
last year, you will probably have it again this year. Proper mowing, fertilization
and irrigation to create a dense lawn will help to control sandbur. A
number of preemergence annual grass herbicides are labeled for control
of sandbur, including DCPA (Dacthal) and products containing pendimethalin.
Preemergence herbicides applied in spring to prevent crabgrass should
also prevent sandbur. Homeowners can also use products containing MSMA
for selective control of sandbur. If there is not enough grass on the
area to justify a selective control (a playground or sandbox for example),
Roundup or Finale can be used to nonselectively control sandbur.
Q. I have been told that cut up leaves are good for flower beds. So this
year I had the mower cut up the leaves and had them dumped on the flower
beds. When is the best time to work them into the soil? Should I do it
now or wait until spring? Another question: I have many pots around my
house and patio. What about changing the potting soil? Is this something
that should be done every year? Every five years? I would appreciate any
help you can give me. -- Sue Wessels, Lawrenceburg, Ind.
A. Work the leaves into the soil when the ground becomes workable in the
spring, taking care not to damage any existing perennials or spring bulbs.
In the future, you can do this in either fall or spring. Chopped leaves
add important nutrients and improve soil structure.
If your container plants have any diseases, the soil should be discarded
at the end of the growing season. If your plants appear healthy, the soil
can be saved and reused but realize the nutrient level is depleted with
each year of growth. A liquid or granular fertilizer program should be
followed when reusing soil. Also, the soil should be loosened before replanting
each year. Every few years, or when plants seem to grow less rapidly,
replace the soil with fresh potting mix.
1-6-05
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