Factor Plus Status Mixes to Control Annual Ryegrass
There has been increasing publicity of late regarding mixes of two Group A “dim” herbicides to improve the control of annual ryegrass. Mixing Factor (Butroxydim) and Status (Clethodim) has been reported to lead to increased control of ryegrass populations with developing levels of resistance to Group A herbicides. Whilst these reports are correct and trial data has shown improved levels of control with these mixes, there are a few important points to note:
There is a relatively small quantity of Factor produced annually, which tends to sell out early in the season.
Some trials have been conducted using the top label rate of Factor (180 g/ha), whereas the maximum label rate on canola is 80 g/ha. This rate restriction is due to the risk of crop damage associated with higher rates. Therefore field results may not be as spectacular as those demonstrated by trial data.
As both products are Group A “dim” herbicides, the greatest improvement in control from mixing the two is likely to occur where there is a low level or developing resistance. In situations where there is a highly resistant population, the increased level of control achieved by mixing Factor with Status may only be small.
Mixing the two products together will increase the rate at which resistance develops, as the survivors are likely to be highly resistant individuals. Therefore, this is a very short term solution which should only be used in conjunction with either one or more of crop topping, brown manuring, windrower cutter bar spraying, or windrow burning, in order to control as many survivors as possible. Mixing Factor and Status is not a sustainable solution to ryegrass control!
Factor is only effective on very small ryegrass (2-3 leaf), so timing is critical. Status alone has a wider application window.
Ideal rates for such mixes are in the order of 80 g/ha Factor plus 400 ml/ha Status. In canola, application should occur once the crop is at the four leaf stage (4th leaf fully expanded) and before flower buds become visible.
In certain conditions, both Factor and Status can cause significant crop damage in canola.
Any stress on the weeds will lead to reduced efficacy. A combination of stresses can result in very poor performance. Such stresses include:
a) Moisture stress
b) Heat stress
c) Frost
d) Chemical effect, particularly from Atrazine and Simazine
9. Frost incidence in the 2-3 days post application may lead to a significant reduction in efficacy. This applies to all group A herbicides, but especially “dims”.
10. Tank mixing with Triazine herbicides will reduce efficacy.
Mixing Factor and Status can be a tool for controlling annual ryegrass, however it must be used in an integrated weed management program to maximise the efficacy and longevity of control achieved.
It should be remembered, that these are all bandaid solutions. Sustainable ryegrass management involves a strategic systems based approach.