GRDC - Research Summaries - WAWHT 2525A tolerates metribuzin well
| Date: 01 Feb 2004
*Note - this report may contain independently supported projects, which complement the work in this GRDC research program.
Take home messages
- WAWHT 2525A has metribuzin tolerance similar to Blade. It tolerated up to three times the registered rate of metribuzin very well.
- When registrations are completed, wheat growers can manage barley grass, brome grass, silver grass, ryegrass, toadrush, wild radish, capeweed, doublegee and wire weeds in this variety by using metribuzin alone or its mixtures with trifluralin and diuron.
- In lupin-wheat rotation, this variety can be the best option following lupins if due to any reasons metribuzin residues may be of concern.
Metribuzin belongs to herbicide group C (sub group triazinones). Lexone (metribuzin) @ 200 g/ha is registered for use in 'Blade' wheat in the Great Northern region of WA to control brome grass, capeweed, doublegee, wild radish and wire weed.
To achieve good control of barley grass and annual ryegrass Lexone 200 g + Trifluralin 1.0 L/ha has also been registered. Recently released and commonly grown wheat varieties are sensitive to metribuzin at the rates that gives good control of the weeds.
WAWHT 2525A seemed to be tolerant to metribuzin. It has Blade as one of its parents (Blade*2/Sunelg). The objective of the trial was to evaluate sensitivity/tolerance of WAWHT 2525A to metribuzin in comparison to Blade (known tolerant) and Camm (known sensitive).
|Location and year||Mullewa Research Station, 2003|
|Soil type||0-10 cm: Sandy loam (82% sand, 7% silt and 11% Clay)
10-20 cm: Loam (78.5% sand, 7.5% silt and 14% clay)
|Soil pH (Cacl2) and EC (mS/m)||0-10 cm: 6.4 and 9
10-20 cm: 7.4 and 22
|Trial design||Crisscross, two untreated controls in each replication|
|Plot size and replications||10 m x 3 m and 3|
|Sowing date Seeding machinery||6 June 2003 Knife points followed by press wheels and finger harrows|
|Seeding rate||57 kg/ha|
|Fertiliser||Agras 100 kg/ha at seeding, top dressed with 50 kg/ha Urea on 11 July|
|Herbicides application date||6 June 2003, all herbicide treatments were incorporated by seeding|
|Moisture levels (%) (Gravimetric method, 4 samples per replication)||Depth
|At field capacity
|At crop seeding
|Wheat plant count Wheat head count||24 July, 33 cm x 33 cm quadrat used, 2 randomly selected spots per plot
13 October, same procedure used as in plant counts earlier
|Blanket sprays||Bromoxynil 2 L/ha applied on 8 August as radish in high density was appeared mainly in control plots. Weeds were effectively controlled at very young stage by this treatment and weed free conditions were achieved. Fastac 100 125 mL/ha applied on 16 September to control aphids.|
|Harvesting date||November 2003|
|Total rainfall (mm) June-November||161.8|
Effect on plant population and number of ear heads
Plant counts taken six weeks after seeding indicated that numbers were significantly less in Camm than Blade and WAWHT 2525A. No variety was affected by 150 g/ha, but seedling numbers of Camm began to drop off significantly at 200 g/ha. Blade and WAWHT 2525A numbers were not affected until rates of 600 g/ha, by which time Camm numbers were down by 79%.
Head counts suggested that compensating growth of Camm had occurred. At 200 g/ha this fully compensated for seedling loss, and partly so at higher rates (Table 1). At 600 g/ha, while plant numbers were reduced by 79%, head numbers were 'only' down by 57%.
Effect on grain yield
None of the Lexone rates tested caused significant yield reduction in Blade and WAWHT 2525A compared to their untreated controls (Table 1 and Figure 1). At each rate of Lexone WAWHT 2525A yielded at par with Blade. Lexone 600 g/ha caused significant yield reduction in Camm compared to its untreated control and all the other Lexone rates (Table 1, Figure 1). Even though at Lexone 600 g/ha rate, plant population and heads numbers were significantly less in Blade and WAWHT 2525A, grain yield was at par with untreated controls. Reductions in plant population and heads might have been compensated with more grains per head or/and bigger grains.
The fact that such compensation was seen in this trial should not be taken as encouragement to use metribuzin on sensitive varieties. Compensating growth depends on good seasonal conditions, and will not happen every year. In previous tolerance work, metribuzin/trifluralin has reduced yields by 30% at Mullewa (1997) and 37% at Merredin (1998), but by only 9% at Mullewa (1998) and 7% at Merredin (1997). It cannot be predicted.
- Field and glass house (data not shown here) trials revealed that WAWHT 2525A possessed metribuzin tolerance similar to Blade. This variety has preliminarily been classified as AH, has low screenings, acceptable black point, good falling number and triple rust and powdery mildew resistance.
- This wheat variety can be grown specifically in the paddocks where barley grass, brome grass, silver grass, ryegrass, toadrush, wild radish, capeweed, doublegee and wire weeds are the problem weeds. Metribuzin alone or in mixture with trifluralin and diuron effectively controls these weeds.
- In lupin-wheat rotations, this variety can be the best option following lupins if due to any reasons metribuzin residues may be present.
|Herbicides/ha||Plant population (6WAS)||Number of ear heads||Grain yield|
|Blade||WAWHT 2525A||Camm||Blade||WAWHT 2525A||Camm||Blade||WAWHT 2525A||Camm|
|Lexone 150 g||96||97||97||96||96||92||100||99||100|
|Lexone 200 g||98||96||69||93||94||96||103||100||105|
|Lexone 300 g||97||95||68||97||96||88||100||100||94|
|Lexone 600 g||78||81||21||78||84||43||102||102||69|
|LSD (0.05) Lexone v/s untreated||19||18||26||16||16||17||15||16||17|
|LSD (0.05) Lexone rates v/s rates||21||20||28||19||18||20||18||18||20|
|LSD (0.05) Untreated v/s untreated||19||43||195|
WAS: Weeks after seeding.
All the herbicide treatments were incorporated by seeding.
Figures in bold are significantly different from untreated control.
Figures in parenthesis are the wheat plant numbers m-2, ear heads m-2 and grain yield kg/ha.
Figure 1. Grain yield of WAWHT 2525A and Camm as % of Blade grain yield under different herbicide treatments.
We are thankful to Mr Mario D'Antuono, biometrician, for his help in statistical analysis.
Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994.
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