Secrets of a clean kill

Rachel Carson, the visionary author of the 1960s classic 'Silent Spring', was right - even with the best intentions and delivery, there is still a good chance that chemicals will have some form of negative local impact. Chemicals can pollute waterways and kill wildlife such as frogs, and if overused can lead to resistance in the very plants we are trying to control.

Consequently, it makes sense to develop good strategies to guard against these effects. To use chemicals effectively and safely, use the following guidelines.

_Follow instructions _

It is amazing that I have to remind people of this, but read the labels and never use more than the rates recommended by suppliers - more does not mean better.

For example, overdosing glyphosate can do more harm than good. It is a salt-based chemical, so if you increase the rate to tackle what you believe is a big problem, the plant reacts as it would to salty water; it shuts up its stomata and takes nothing in.

Wasted chemical, wasted opportunity. So much so that professional weed control agents have informed me they consistently get excellent results using less than the recommended rates, by making sure that their brew includes the right additives and that the plant is actively growing when they hit it.

This may seem counter-intuitive, but they informed me that a heavier dose, while appearing to deliver a quick response - a noticeable browning off, for instance - probably means the leaves have been burnt but the main body of the plant remains unaffected.

However, if they use a lower dose, they trick the plant into taking a drink, and though it takes longer to see a result - sometimes up to three weeks - this means the herbicide has done its job, effectively sending the plant to 'meet its maker'.

_Super response recipe _

Building on this weeding wisdom is some insider information on how to get a really good kill, even with notoriously tough weeds like couch and kikuyu.

Add a teaspoon of wetting agent such as Grosorb as well as a teaspoon of urea to every litre of herbicide mixture. This super brew will not only increase chemical absorption and effectiveness but it will minimise the impact on the environment. A win-win situation.

_Stay on target _

Spray a width of 1.5m to 2m, centred on the proposed planting line or planting hole.

Weeds should only be sprayed when young and actively growing, so don't leave weed control too late into winter.

Spraying plants that are flowering is usually a waste of time, because the active growth stage is finished - unless, of course, you are dealing with bulbous weeds.

Avoid chemical drift onto non-target areas by spraying only on still, clear mornings when a period of at least six to 12 hours of fine weather is expected.

If spraying weeds that have reappeared within seedlings, then spray with a knockdown herbicide such as Finale, which will only kill what the chemical touches.

Buy a specially designed spray shield to fit over the nozzle or, for something more homemade, use a bucket or a sheet of tin to cover the plants you want to protect. Of course, tree guards give you an excellent protection against spray drift.

When spraying near waterways, use specially formulated chemicals that are better suited to sensitive environments, such as Roundup Biactive.

_Use quality water _

When you are filling the spray tank, only use rain or high-quality tap water. Dirty water from dams or dodgy old tanks will be full of contaminants that will stick to the active herbicide and render it useless.

_Be a luna-tic _

It used to be the domain of what detractors would dub 'the loony left', but increasingly more research is showing that if you time your planting and weeding efforts with the appropriate phases of the moon, the results can be remarkably improved. So get yourself a Moon Calendar and follow it - you won't be disappointed.

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