4 September 1998

Find a partner for ipu

PARTNER isoproturon with another autumn herbicide to boost weed control and cut the risk of residues entering watercourses, advises manufacturer Cyanamid.

"If you intend to base your weed programme exclusively on ipu, cutting levels will seriously affect control," warns product manager, Rob King.

Blackgrass control trials in 1996 in which untreated plots contained 605 heads a sq m prove the point, he continues. At the reduced ipu rate of 1.5kg/ha alone 82% control was achieved. But adding 1.5kg (3.75 litres/ha) of pendimethalin (Stomp) increased control to 97%.

"Just eight blackgrass plants a sq m can reduce yield by 2%. In this case, using lower rate ipu would leave 109 plants a sq m."

Some growers add trifluralin (Treflan) and use it in sequence with tri-allate (Avadex). Although that offers better control than ipu alone, it costs over £40/ha, says Mr King. Pendimethalin costing about £8.50/litre and applied at 3.75 litres/ha, with 3 litres/ha of ipu, gives comparable control, but at a lower cost.

"The yield benefit of the pendimethalin + ipu over straight ipu is 0.6t/ha. At current grain prices this equates to an extra £39/ha, easily paying for the more expensive input." &#42