Controlling stacked resistant radish with herbicides

Controlling stacked resistant radish with herbicides

Grant Thompson, Crop Circle Consulting / Landmark, Geraldton.

Key messages

• Herbicide resistant wild radish can be controlled well by a range of herbicides if applied early when weeds are small.
• A two-spray strategy has proven to be very effective at controlling problem wild radish, particularly when the first spray is effective and is done as early as possible on small weeds with a reliable mode of action.

Aims

Determine what herbicide mode of action and application strategy will best control a known multiple herbicide group resistant wild radish population.

Method

1. Trial 1 (HUSBANDS) was at Paul Husbands farm in Northampton. This site was resistance tested by Elders and Plant Science Consulting and found have concerning levels of resistance to 4 herbicide groups. First Spray Treatments at 2-leaf of the wheat crop – applied with a TEEJET AIXR11002 nozzle at 60 L/Ha, 600KPA and 12 km/hr.

1. Nil    2. 1500 ml Bromicide® 200    3. 1000ml Jaguar®   4. 670ml Velocity® + 1% Hasten®

Table 1 Layout of first spray treatments (T1) applied at 2 leaf of the wheat crop.

The second spray treatments were applied at 5 leaf – applied with an AGROTOP AIRMIX 110 01 nozzle at 2 bar at 98 L/Ha at 4 km/hr.  The second treatments were applied at right angles across the first spray treatments in what is known as a criss-cross trial pattern.

Resistance Profile of the trial site population:

Glass House Resistance tests by Plant Science Consulting / Belinda Eastough (Elders):

100% survival to 40g Logran® (B)                             45% survival to 2L Simazine (C)

0% survival with 1400ml Bromoxynil (C)                   85% survival to 200ml Brodal® (F)

0% survival with 500ml Velocity® (H,C)                    60% survival to 650ml 2,4-D Ester (I)

Table 2 Second Spray treatments (T2) applied at 5-leaf of the crop, over the top of the 2-leaf treatments¹.

¹This layout then achieved a trial that had 56 (4 x 14) treatments of 9m x 2m area, replicated 3 times. Some of the treatments above are currently unregistered.

Results

The data in Table 3 clearly demonstrates the success of the 2 spray strategy when Bromicide 200, Jaguar and Velocity were used at the early 2 leaf (T1) timing. When no late spray was used to clean up survivors, Velocity was the most reliable early spray, as indicated by 97% and 100% weed control in the two nil late spray treatments (Trt 1&14).  At 10 days after Treatment 2 (T2), Velocity® at 800ml, Tigrex® + Ecopar® and Precept 150® + Ecopar® gave significantly higher crop phytotoxicity results (p<0.05) than the other treatments.

When there was no early spray applied, the later 5-leaf sprays (T2) were put under a great deal of pressure. With approximately 200 radish plants/m², there was shading of radish by other radish in many plots. If the treatment did not contain a systemic mode of action, then some of the contact only modes of action were put under more pressure. This is demonstrated by the one late spray of 800ml of Velocity® at 5-leaf achieving 93% control, but an early spray at the 2-leaf stage on much smaller weeds achieved 100% control. This trial also shows that most treatments recommended by the RCSN group were successful in controlling this population, even in light of the very high levels of resistance present in the test results.

Table 4 shows that a yield advantage of 400-500 kg/ha was consistently achieved if an early 2-leaf spray (T1) of either Bromicide 200®, Jaguar® or Velocity® is followed up with any number of the 5-leaf spray (T2) options. Yields ranged from 2.63 - 3.06t/ha when only one late T2 spray was applied. When the two-spray strategy (T1 & T2) was implemented, yields ranged from 3.1-3.64 t/ha throughout the trial. In one case, the combination of an early Bromicide 200® spray at T1 took the yield of treatment 12 (FMZ1209 + Bromicide MA® at 5-leaf) from 2.63t/ha to 3.64 t/ha, which was a yield increase of 1.01 t/ha. Given a radish density of 200 plants/m², these results demonstrate the importance of spraying early for improved efficacy and yield benefits.

Treatment 1 & 14 (no late sprays) shows how effective the early spray choice is on removing radish and preserving grain yield. In treatment 14, with no spraying at all, the crop yielded 1.91t/ha. The early Jaguar spray with no T2 treatment yielded 3.10 t/ha. Early Bromoxynil with no T2 yielded 3.21t/ha. The early Velocity® treatment with no T2 spray yielded 3.47 t/ha.   This is similar to the project findings in 2012 that also showed that Velocity® was the preferred first spray for optimum yield.

Table 3 Crop Phytotoxicity (%) 11 Days after Application (DAA) of T2 Treatment and Efficacy (% plant death) at 11 and 105 Days after T2 Treatment at HUSBANDS Northampton.

Table 4 Crop Yield (t/ha) and yield (%) compared to nil of all treatments at the HUSBANDS site at Northampton.