• A weed is defined as a plant growing out
– Weeds grow faster than crops
– Produce lots of seed with long viability
– Usually have some seed dormancy
– Some can also reproduce vegetatively
– Some weeds have allelopathy
Cultural Weed Control
• Most garden weeds are removed manually
– Long term weed control is accomplished by
not allowing weeds to set seed in the garden
• Manual = pull, hoe, till, plow, chicken
tractor, weeder geese
• Don’t allow weed seed to germinate
– Mulch, corn gluten, salt
Manual weed removal
• Most weed seed needs light to germinate
• Organic mulch – straw, leaves, Hosta
Squash… can keep light from hitting the
soil surface and keep weeds from
• Black plastic
Biological weed control
• Using animals
• Crop competition
• Introducing insects or diseases
Let others do some of the weeding!
• Large leaved crop or ornamental plants
like squash or Hosta will shade out weeds.
• Peas are one of the crop plants that are
allelopathic and can fight weeds
Using insects and disease
• Be very careful with these!
– There is a new patent on a fungus that
selectively kills crabgrass.
– The DNR is releasing a small beetle that eats
• Herbicides can be classified as:
– Contact or Translocated
• Contact=plant is injured at the point of contact
• Translocated= (roundup) goes into the plant leaves
and kills roots and rhyzomes
– Residual and non-residual
• Residual= has some long term soil activity
• Non-residual=does not
Herbicides. During the fallow period, oxyfluorfen (GoalTender) can
provide both preemergent and postemergent control of winter weeds.
Paraquat (Gramoxone), pelargonic acid (Scythe), glyphosate
(Roundup), and carfentrazone (Shark) can provide fallow bed weed
Metam sodium is available as a soil fumigant to control soilborne
diseases and nematodes, but it can also be used to control weeds,
although results are not always consistent. Be sure the soil is well
cultivated and moist before its application.
Also available are paraquat (Gramoxone Inteon), pelargonic acid
(Scythe), and glyphosate (Roundup) to control emerged weeds before
planting. Glyphosate as a preplant treatment can be particularly
helpful in controlling perennial weeds.
The preplant herbicide benefin (Balan) is mechanically incorporated
into the top 2 to 3 inches of the lettuce bed. Because benefin remains
in the soil after harvest, do not plant benefin-sensitive crops such as
corn, sudangrass, sugarbeets, spinach, and sorghum, following a
lettuce crop where benefin was used. Depth of incorporation is
important to the performance of this herbicide. If it is incorporated too
deeply it will dilute the herbicide, resulting in poor performance. Mixing
it too shallowly may reduce lettuce tolerance. Power driven
incorporator, bed shaper units have given satisfactory results.
Chemicals for Home Gardens
• The rules for herbicide use change every year –
mainly chemicals are finally tested and found to
be cancer causers – or worse
• If you use these you must read the whole label.
• Wear the proper protection , don’t apply on a
windy day, keep away from streams and other
• Don’t put anything on your food that you don’t
want to eat
Eat your weeds