PLANT PROTECTION 1 – Pests, Diseases and Weeds

PLANT PROTECTION 1 – Pests, Diseases and Weeds
HERBICIDE APPLICATION.
HERBICIDES
MAY BE USED TO
TREAT
TREATMENTS
FORMULATIONS
SURFACTANTS
Adjuvants
PLANTS AND SOIL
The foliage. These herbicides are commonly applied to leaves, stems, apical
shoots, etc as sprays, aerosols and wipe-ons. They may have contact action, eg
Shirquat (paraquat) or be systemic, eg Roundup (glyphosate).
The soil. Herbicides may be applied as sprays or granules. They are usually
systemic, persist for long periods, are taken up from the soil by germinating seeds
and established weeds. Some have pre-emergent selective activity at low rates,
but provide total vegetation control at higher rates, eg simazine.
The trunks of trees, etc. These herbicides are commonly applied as liquids in
holes or cuts in stems. They must be systemic to be taken up in the sap stream, eg
Roundup (glyphosate), Garlon (triclopyr).
TREATMENTS include:
Broadcast treatment. Cover an entire area (plants and/or soil surface) evenly,
either by spraying a liquid or spreading a granular herbicide.
Band treatment. A relatively narrow band is treated with herbicide, eg a crop
row, along the edge of paths. Weeds between crop rows can also be controlled by
cultivation, mowing, etc.
Directed spraying. Herbicide is applied directly to the area between plants, or
inter-row area, care being taken to avoid any contact with the crop plants.
Spot treatments are directed to the foliage of weed clumps in weed-free areas,
eg orchards or wiped on the foliage of individual weeds in lawns or garden beds.
Containers may be spot treated. Also used in pastures, non-crop situations to reduce
the amount of herbicide used.
COMMON FORMULATIONS which
can be purchased include:
Liquids, eg liquid carriers:
– Dry flowable concentration
– Water dispersable granules
– Emulsifiable concentrates
– Suspension concentrates
– Liquid concentrates
Solids, eg solid carriers:
– Soluble powders, water soluble
granules, some are pre-packaged
The formulation is the
– Wettable powders
product purchased
– Dusts
– Granules
Others, eg aerosols, gels. Herbicide-coated fertilizers have been found to be
effective in controlling weeds while reducing runoff.
SURFACTANTS include wetters and stickers which may be added to herbicide
formulations either during manufacture or just before application when needed.
Make water-based herbicides ‘wetter’ so that they stick to and spread over waxy
or hairy leaf surfaces rather than forming into drops and rolling off like rain drops
(pages 444, 445).
Increase the rate of absorption of the herbicide through leaf surfaces thereby
reducing selectivity. A change in droplet size can have the same effect. Surfactants
may affect the final site of action in the plant.
Only add surfactants if the label recommends it, and only use recommended ones,
otherwise crops may be damaged and weed control ineffective.
Carriers (materials used to dilute the herbicide prior to application) such as diesel
enable better penetration of herbicides, used for basal bark treatments.
MARKER DYES Marker dyes are used to indicate spray coverage (page 456).
440 Weeds - Integrated Weed Management