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Post-emergence and Pre-emergence Weed Killers - What are They?

Posted in Garden Advice on July 02, 2015

Kill Existing Weeds and Stop Weeds Growing 

Post-emergence weed killers such as Weed Weapon Rapid Action , Weed Weapon Extra Strength and Weed Weapon Natural Power are applied after weeds have sprouted and emerged above the soil surface. They are most effective when weeds are still small: less than 10 cm tall. Some herbicides (e.g. simazine in Kiwicare Weed Weapon Preventer and Weed Weapon Long Term) have both post-emergence and pre-emergence activity if they reach the soil through direct contact or by washing off the foliage.

Pre-emergence weed killers such as Weed Weapon Preventer are applied before the weeds sprout through the soil surface. Generally speaking, to control warm-season annual weeds, apply a pre-emergence herbicide in early spring (September to November) before the soil temperature has warmed to 10°C. For weeds that tend to sprout throughout the summer, a second application may be required in January or February. To control cool season annual weeds, apply a pre-emergence herbicide in early autumn (March to April). It is difficult to target a particular calendar date for pre-emergence applications due to variable soil temperature and moisture conditions from year to year.

Weed Weapon Long Term is a combination of a pre-emergence and post-emergence herbicide to kill existing weeds and prevent new weeds emerging for a period up to a year thereafter.

By David Brittain

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