The first item of business is to know what type of weeds you want to
control. This will make a big difference in what product or products
you select. The main products used for broadleaf weed control in
lawns are 2,4-D, MCPP, dicamba, a combination of those three
products, and triclopyr.
Let's start with the triclopyr since it's
probably the easiest to discuss. Its place in weed control is for
hard-to-control weeds and woody plants. It also improves control of
violets. It can be combined with one or more additional chemicals to
provide broad-spectrum control. Some blends now contain triclopyr,
so check the label.
The old standby is 2,4-D. It is good on carpetweed, chicory,
dandelion, lamb's-quarters, plantains and wild carrot. MCPP is good
on chicory, lamb's-quarters and white clover. Dicamba is good on
black medic, chickweeds, chicory, dandelion, dock, henbit, knotweed,
lamb's-quarters, pearlwort, purslane, red sorrel, thistles, white
clover, wild carrot and yarrow. The combination of all three
products will pick up all of those listed for the individual
products, plus a few more such as mallow, speedwell and wild onion.
The combinations are sold under many different trade names, so check
the active-ingredient list for ones you need.
My annual disclaimer for application of these types of products
is: "Beware of potential drift from these products." Not only can
the spray move under windy conditions while you are spraying, but
particularly with dicamba in hot and humid conditions, the products
can drift as a vapor for up to two weeks after spraying.
Cedar apple rust
Cedar apple rust is caused by a fungus that attacks two different
groups of trees. The first group is apples and crabapples, and the
second is juniper and eastern red cedar. In order to survive, the
fungus must "move" from one group or host to the other.
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On juniper, or eastern red cedar, small galls (3/8 to 1 3/16 inches
in diameter) develop throughout the tree on needles and small twigs.
When mature, these galls swell considerably and repeatedly produce
orange, jello-like horns during rainy spring weather. As spring
rains subside, the galls die, which may cause death of the twig from
the gall to the tip.
On susceptible crabapples and apples, tiny yellow spots appear on
the leaves after infection in the spring. As the spots mature, they
become yellow-orange and swollen, with a red border, and develop
tiny black dots in the center of the lesion. By midsummer, small
cuplike structures with tubes are visible on the undersides of
mature leaf lesions. The fungus may also infect fruit and tender
twigs of very susceptible crabapple and apple varieties.
The entire life cycle takes about two years, with a year on each
host. The apple phase is easily recognized on the leaves and fruit
by just about anybody who has grown apples. The teliospore phase on
the cedars is quite striking, but is noticed much less frequently.
Fungicides in spray programs do a good job of controlling the
apple phase, while the cedar phase is best controlled by buying
resistant varieties. Some homeowners cut the galls off before they
break out into the "orange blob," but the result is the same: You
are likely to lose the tips on those branches.
University of Illinois
Extension director for Logan, Menard and Sangamon counties]