WEEDS & WEED CONTROL
Understanding weeds and learning how to control them
One of the greatest
challenges in landscaping and gardening is weed control. There is an appropriate
saying, "Nature despises a void." This certainly applies to bare,
might not have realized is that weeds can attract and harbor destructive insects.
While studying Nursery Plant Culture at Penn State, we learned that a commercial nursery
should be weed-free. Not just for "looks" either. . .
knew that weeds compete with desirable plants for water, light and nutrients, but what we
learned was that weeds can also provide a home for "vectors."
"vector" can be defined as "an organism that carries pathogens from one
host to another." In this case, pathogens would be destructive plant insects,
such as aphids, among others.
definition of a weed is "a plant out of place." OK
then, following that line of thinking....
If a dandelion is a weed in a home lawn,
grass is a weed on a dandelion farm!
(where they grow dandelion greens)
LIFE CYCLE: ANNUAL VS. PERENNIAL
those weeds which complete their life cycle within one growing season, or year. The
most familiar example of an annual would be crabgrass, which germinates from seed in the
spring of the year. Crabgrass germinates when the soil temperature reaches
50-degrees F. (An easy way to remember when this occurs is that crabgrass germinates
when Forsythia is in full-bloom).
See you next
completes its life-cycle in the fall; the mature plant produces seeds and is killed-off by
the first hard frost of the fall. The seed remains in the soil to germinate the
following spring when growing conditions are right. This defines a summer annual.
annuals are very similar, except they germinate in the fall and die in the early heat of
summer. Annual bluegrass would be a good example.
are those weeds which live on, from year-to-year, and may appear to die-off in the fall
like an annual does, but their roots remain alive, in a semi-dormant state through the
winter months. Fresh foliage reappears from the overwintering root system the
following spring. Dandelions would be a good example of perennial weeds. (It
is worth noting that dandelions spread and reproduce from seeds as well)
WEED TYPES: BROADLEAF VS. GRASS
dandelion is probably the best example of a broadleaf weed. The leaves are
"broad" as opposed to the "narrow" leaf of a grass
plant. In technical terms, broadleaf weeds are 'dicots' having two seed
leaves, while grassy weeds are 'monocots' having one seed leaf.
Plantain is also
a very common
broadleaf weed in lawn areas
bascially two methods of removing dandelions from a lawn; the first is hand-digging to
remove the tuberous root (which will produce another plant if it isn't fully removed), and
second, the application of herbicides (commonly known as "weed killers").
grasses share similar appearance to cultivated grasses, while the most noticeable weedy
grasses tend to be coarser textured ones. One of the most bothersome grassy weeds is
annual bluegrass (a winter annual), which intermingles with desireable grasses on golf
courses, and thrives on the care and maintenance golf course turf receives.
annual bluegrass and crabgrass can be controlled with properly timed pre-emergent
herbicides (at different times of the year), perennial weedy grasses have to be
hand-pulled or treated with non-selective herbicides. This creates obvious problems
when the weedy grasses are intermingled with desirable grasses in a home lawn.
Volumes have been written concerning the potential dangers of chemicals in our
environment, including herbicides and insecticides, which come under the general heading
of "pesticides." The reader will have to make his or her own determination
of whether or not they choose to use chemical weed controls.
implying an endorsement of herbicides here, our purpose is to discuss the basics of
chemical weed control used by most professionals in the "Green Industry".
For those of us who have studied pesticides, become state licensed applicators, and
applied pesticides commercially, four words become the gospel truth:
ALWAYS READ THE LABEL!
labels are full of critical information covering all aspects of use, handling and storage
of the product. Be sure to FOLLOW LABEL
INSTRUCTIONS. For some strange reason, people
mistakenly think that if one tablespoon of 'Pesticide X' per gallon is good, two
tablespoons has to be better. WRONG! The recommended rates have been
established through extensive testing and field trials. Doubling the usage rate of
any pesticide is illegal, and probably will be counterproductive, by not producing the
labels contain important information you need to know. Spend the required 10 or 15
minutes necessary to read and understand the label -- this will help ensure desired
Sprayer Safety Tips
pesticides out of the reach of children
use the same sprayer for weed control and insect control applications.
Mark one sprayer "WEEDS."
a low pressure regulator to help prevent spray "drift" onto
applications in the cool of the day when there is little to no wind.
when no rain is forecast for 24 hours unless the product calls for
properly: Protect eyes and skin, wear approved chemical resistant
gloves and boots, and wear an approved respirator if possible.
of the greatest risks is handling the concentrate, so wear approved
gloves and be sure to protect your eyes from splashing.
empty pesticide containers into your sprayer and dispose of containers
contain signal words which tell the user the level of toxicity: The least toxic
chemical pesticides are labeled CAUTION.
Middle level toxicity is indicated by the word WARNING.
The most toxic pesticides are labeled DANGER/POISON.
toxic pesticides usually require a pesticide license to purchase or apply. It is
always advisable to use the LEAST toxic pesticide available to treat your particular need.
YOUR CHILDREN SAFE?
#1 cause of pesticide poisoning in children is oral exposure. NEVER
transfer a pesticide from its original packaging and never put a
pesticide in an old beverage container!
individuals are "hypersensitive" to pesticides that cause little to no reaction
in other people. The State of Pennsylvania sends a quarterly "Pesticide
Hypersensitivity Registry" of hypersensitive individuals to all commercial pesticide
applicators in the state. There is a mandatory process for commercial applicators to
provide advance notice to these individuals when an application is to be made within 500
feet of their work, school or residence.
doctor can medically certify that your name should appear on this hypersensitivity
registry list, contact:
Dept. of Agriculture (PDA)
Bureau of Plant Industry
2301 N. Cameron St.
Harrisburg, PA 17110-9408
Main Phone: (717) 772-5231
-or- Peg Zubeck (717) 772-5207
If someone in your family is
hypersensitive, it would also be a good idea to notify your neighbors. Commercial
applicators know about registered individuals, but your neighbors might not.
two terms describe the "action" of a particular herbicide.
"selective" herbicides are those types used to control broadleaf weeds (like
dandelions) in your home lawn. They are considered selective since they only kill
selected, or target weeds, when they are properly applied.
Applying the proper rate is very important since a higher rate may not be
selective, killing more than just the target weeds. In other words, your lawn grass
may tolerate the labeled rate of weed killer it takes to kill a dandelion, but at a higher
rate, the grass could be burned and adversely affected as well.
herbicides can kill any plant they touch, without being at all selective. These
herbicides are most commonly used for controlling weeds that aren't intermingled with
desireable plants (weeds that are "out in the open" so to speak).
Non-selective herbicides are used to control vegetation along highways, power lines and
TYPE OF APPLICATIONS
these terms helps to understand the type of herbicide you need to control a particular
implies controlling the weed, or weed seed, before it "emerges" or germinates.
In actuality, some pre-emergents control the weed seed right after it germinates,
by killing the young, delicate, emerging roots.
implies controlling the weed after it has "emerged" or germinated.
Post-emergent weed controls are most effective when applied to a weed that is
"actively growing" (not to a weed that is under drought stress or in a
semi-dormant state). Many herbicides have "systemic action", moving from
the plant leaf down to the root, and throughout the plant. This movement occurs best
during periods of rapid plant growth.
This page attempted
to cover the basics of a very complex subject and the information may be
incomplete. We're not responsible for any errors or omissions.
ALWAYS READ AND
FOLLOW LABEL DIRECTIONS!
1993, the Pennsylvania Department of Agriculture has hosted a program known
as CHEMSWEEP. On a rotating basis from county to county, and year to year,
individuals can safely turn over their old or unwanted pesticides to
authorized personnel for safe disposal. Protect our environment by safely
disposing of your pesticides.
Using herbicides and pesticides