Weed-free solutions

27 November 1999

Weed-free solutions

New research into herbicides should keep weeds at bay, says Tom Allen-Stevens.

ESTABLISHING trees can be costly. But if you lose your establishment grant because most of them die, the cost can be crippling. Moisture, nutrients and light are crucial to a trees establishment during the first three years of its life. Competing for these are a trees biggest killers: weeds.

"Trees should be grown in a one-metre wide weed-free environment for the first three years of their life. The problem for most farmers is how to provide this," explains UAP agronomist and environmental specialist Marek Nowakowski.

Standard practice is to ensure the site is weed free before planting by spraying off with Roundup (glyphosate). After planting, the site can be over-sprayed with a number of approved herbicides while the trees are dormant. The most common ones that currently have off-label approval are Fusilade (fluazifop-P-butyl), Butisan (metazachlor), Stomp (pendimethalin) and Kerb (propyzamide).

Once the leaves have emerged, often the only option is to carefully spray round each tree with glyphosate in a knapsack – a painfully slow job at a time of year when the rest of the farm needs your undivided attention.

This is why Mr Nowakowski has been putting in years of research with UAP, helped initially by the Forestry Commission, to discover what sprays can be applied to a young plantation. The aim has been to remove as many of the competitive weeds as possible without damaging too many trees.

"At the end of the day, it wont matter if you affect a small proportion of your young trees with the spray – after all, more would be lost by doing nothing," he points out. A number of herbicides have been applied to trial plots on UAPs Manor Farm near York. Challenge (glufosinate-ammonium) and Reglone (diquat) have given encouraging results when used pre-bud burst (before April).

"The interesting bit of the work is using these total herbicides over the tops of the trees without harming them. Weve also had some very positive results from using Galtak (benazolin) and Eagle (amidosulfuron) post-bud burst," Mr Nowakowski maintains. He is hoping to gain off-label approval for the herbicides from the Pesticide Safety Directorate (PSD) early next year.

Other research has focused on the gaps in between the rows. This inter-row vegetation can play an important part in controlling pernicious weeds, as well as being a valuable haven for wildlife. If this area is just naturally regenerating, Mr Nowakowski recommends topping it regularly until the annual weeds have gone.