Horticulture Principles and Practices

6. Weather factors. Although little rainfall may be unsatisfactory in some situations,
excessive rain may wash granules away. Spraying in windy conditions causes
excessive drift that may damage crop plants.
7. Age of weeds. Herbicides are more effective on younger plants than older ones.
Weed-control measures should be effected before weeds are mature.
8. Soil characteristics. Herbicides such as Dacthal are readily absorbed by the soil
organic matter, making them less effective on soils that are high in organic matter.
Clay soils also absorb certain herbicides. In such situations, a higher rate of application
may be necessary for better results.
8.16 INDOOR WEED CONTROL
Weeds should not become a problem indoors, especially in the home. Most houseplants
are planted in pots or suitable containers. Weeds may occasionally arise because of the
source of the growing medium. Such unwanted plants should be uprooted by hand. There
is absolutely no need to use chemicals to control weeds in the home. In greenhouses
without concrete floors, weeds could become a problem if neglected. Weeds could also
arise through cracks in the concrete. Such weeds may be spot treated with chemicals.
Certain herbicides are approved for use in greenhouses.
8.17 SUGGESTED HERBICIDES FOR THE LANDSCAPE
Common herbicides used in ornamental plant culture are presented in Table 8–7.
8.18 SUGGESTED HERBICIDES FOR THE HOME GARDEN
Weed control in the home garden can be accomplished without chemicals. Annual weeds
(e.g., purselane, pigweed, and crabgrass) and perennial weeds (e.g., bindweed and
quackgrass) can be controlled by hoeing, mulching, cultivating, or pulling by hand.
Chemicals such as Dacthal may be used if necessary.
TABLE 8–7
Suggested Herbicides for the Landscape
Problem Weeds
Lawn
Annual grass weeds
Annual broadleaf weeds
Perennial and other weeds
General control of broadleaf weeds
Flower beds
Annual weeds
Perennial weeds
Around shrubs and trees
Annual weeds
Perennial grass weeds
Suggested Herbicides
Trifluralin
Dacthal (DCPA)—apply as preemergent
Bromoxynil
Glyphosate—as spot treatment; use for nonselective
control or as preemergent for new lawns
2,4-D amine
Dacthal
Eptam (EPTC)
Dacthal, Bensulide
Eptham, Glyphosate
274 Chapter 8 Principles and Methods of Disease and Pest Control