Exploring herbicide tolerance in lentils

Chris Davey,

YP AG

Take home messages

Early vigour is closely related to lentil yield.

Factors that determine the safety of the post sowing pre-emergent (PSPE) application include; lentil variety tolerance, sowing depth, chemical type, soil moisture at the time of sowing and rainfall received after application.

The texture and pH of the soil determines the type and rate of chemical used for weed control in lentils.

The introduction of Herald XT and Hurricane lentils will add flexibility to farmers’ rotations.

Milk thistle and prickly lettuce are both problematic weeds in lentils and require attention to control them before the lentil crop has emerged. Group C chemicals like Diuron, Simazine, Metribuzin and Terbuthylazine all have activity on these weeds.

Introduction

The characteristics of the northern soils associated with the Northern Sustainable Soils farmer group are mainly their light and sandy texture, alkalinity and calcareous nature.

The sandy texture means that nutrients and chemicals are rapidly leached down the profile, and therefore, the selection of chemical rate is difficult due to the leaching nature of the chemical as well. Generally, lower rates are selected for the safety of the crop. The pH of 8 to 9.5 of the soil means that Group B chemicals have long half-lives and do not break down rapidly in the soil. The use of this group has decreased in the past 15 years so farmers have the flexibility to grow conventional lentils in their rotation.

Lower rates of the moisture activated chemicals in all Group C’s used in lentils have to be chosen so little crop effect is observed. The chemical moves quickly in the soil under wet conditions, so the residual properties of the chemical are reduced. This normally results in poorer weed control and some times, crop damage.

Until the introduction of Herald and Hurricane lentils, Group B chemicals with high residual properties were avoided and care had to be taken with rotations.

For the past three years, these trials have been funded by the Northern and Yorke Natural Resource Management board (NYNRM) and the GRDC. The aim of the trials has been to assess the tolerance of lentils to different, and in some cases off-label, herbicides in sandy, light soil types.

Lentils are a high gross margin crop, so careful consideration has to be taken when growing them in such an area. Chemical effect, or crop damage, can result in yield loss, higher risk of erosion over summer, poorer nitrogen fixation, and poorer weed competition.

All of these factors lead to a lower level of sustainability and profitability in the NYNRM region.

The trials started in 2011, looking at some commonly used pre-emergent broadleaf chemicals and their effect on lentils.

2011 results

Table 1. Lentil herbicide tolerance at Port Broughton in 2011

	Pre-emergent	PSPE	Post-emergent	Vigour	Yield	% of UTC
1	Untreated control (UTC)			10.0 a	1.64 a	100
2	Metribuzin 120 g	Metribuzin 60 g		9.7 ab	1.59 ab	97
3	Metribuzin 120 g			9.3 abc	1.51 abc	92
4	Metribuzin 120 g		Brodal® 180 mL	8.3 bc	1.26 c	77
5	UTC			10.0 a	1.64 a	100
6	Terbyne 1 kg			8.0 c	1.46 abc	90
7	Terbyne 1 kg	Terbyne 700 g		5.3 d	0.89 d	54
8			Brodal 240 mL	9.0 abc	1.36 bc	83
9	EXP 1 L			9.3 abc	1.64 a	100
	Co-efficient of Variation			10%	10%
	LSD 5%			1.6	0.25

*Highlighted cells denote NOT REGISTERED and OFF LABEL

Figure 1. 2011 lentil vigour on the 30^th of June versus the final yield.

Summary of 2011 results:

Early vigour is closely related to lentil yield.
Some chemical is preferred, either PSPE or post-emergent, to control broadleaf weeds in the furrow.
The practice of applying a PSPE chemical can however, result in crop damage, yield loss or poor weed control under the wrong conditions e.g. heavy rainfall following application, or lack of rainfall afterwards.
Terbyne was safest when used pre-emergent only. The addition of some Terbyne PSPE severely affected yields. Manufacturers, Sipcam have since released a set of guidelines for use of Terbyne on lentils.
In 2011, Brodal did have some effect on the yield of lentils at Port Broughton. A prolonged dry spell occurred after this application, which may have compounded the effect.
Be aware of stubble loads and the effect it can have on these chemicals.
Levelling the surface can affect the result as well.

2012 results

Table 2. Lentil herbicide tolerance at Port Broughton in 2012

	Pre-emergent	PSPE	NDVI RI%	Yield	% of District Practice
1	Metribuzin 120 g	Metribuzin 60 g	100	1.80	100
2	Terbyne 1 kg		100	1.25	69
3	Terbyne 700 g	Terbyne 300 g	90	1.25	69
4	Simazine + Diuron		104	1.25	69
5	Spinnaker^a + Diuron		106	1.70	94
6		Valor 90 g	94	0.80	44
7	Propyzamide 1 L		140	1.85	103
8	Propyzamide 0.5 L		138	1.90	106

*Highlighted cells denote NOT REGISTERED and OFF LABEL; NDVI RI% = Normalised Difference Vegetation Index – Relative Index Percentage (relative to Treatment 1)

^a Registered for use in SA under permit number: PER14369

Summary of 2012 results

There was an effect from the Terbyne use again for season 2012.
The split application had a worse NDVI than the all ‘up-front’ treatment.
The experimental usage of Valor as a residual chemical would appear not to be advisable.
The increase in NDVI from the use of Propyzamide was mainly from the amount of milk thistles present in these plots. Propyzamide does not control milk thistle. If it does get used in the field, another chemical like a Group C triazine should be added to the tank mix.

2013 results

Table 3. Lentil pre-emergent herbicide tolerance at Port Broughton in 2013

	Pre-emergent	PSPE	Post-emergent	Milk Thistles	Yield	%
1	Terbyne + Propyzamide	Terbyne + Propyzamide		1.8 a	1.47 a	100
2	Outlook 1 L	Outlook 0.5 L		3.3 ab	1.45 ab	99
3	Propyzamide 1 L			6.8 cd	1.40 abc	95
4	Outlook 1 L			8.8 d	1.35 abc	92
5	Terbyne 1 kg			8.8 d	1.34 abc	91
6	Terbyne 700 g	Terbyne 300 g		1.3 a	1.29 bc	88
7	Propyzamide 0.5 L	Propyzamide 0.5 L		5.8 bc	1.29 bc	88
8	Metribuzin 150 g	Metribzuin 50 g		5.0 bc	1.26 c	86
9			Metribuzin 180 g	7.3 cd	0.97 d	66
	Co-efficient of Variation			41%	13%
	LSD 5%			2.5	0.17

*Highlighted cells denote NOT REGISTERED and OFF LABEL

Summary of 2013 pre-emergent herbicide results

Metribuzin used as a foliar application is not registered and can cause severe crop effect.
Terbyne proved to be the best chemical or tank mix partner to control milk thistle.
Factors that determine the safety of PSPE application include lentil variety tolerance, sowing depth, chemical type, soil moisture at the time of sowing and rainfall received after application.

Table 4. Lentil group B herbicide tolerance at Port Broughton in 2013

	Pre-emergent	PSPE	Post-emergent	Yield	%
1	Logran 15 g			1.74 a	100
2	Ally 7 g			1.71 ab	98
3		Spinnaker 70 g	(^areg’d post-em)	1.64 abc	94
4		Intervix 750 mL		1.55 abc	89
5		Broadstrike 25 g		1.50 bc	86
6	Spinnaker^a70 g			1.45 c	83
7		OnDuty 40 g		1.41 c	81
8		Ally 5 g		0.43 d	25
9		Crusader 500 mL		0.28 d	16
10		Glean 10 g		0.23 d	13
	Co-efficient of Variation			18%
	LSD 5%			0.23

*Highlighted cells denote NOT REGISTERED and OFF LABEL

^a Registered for use in SA under permit number: PER14369

Summary of 2013 group B herbicide results

There is a large variation in tolerance to Group B chemicals by Herald XT lentils.
Most of the treatments applied in this trial are not registered for use in lentils.
Herald XT (and Hurricane) lentils are tolerant to Spinnaker at label rates, have increased tolerance to Broadstrike and improved tolerance to residual levels of sulfonyl urea chemicals.
The use of OnDuty, Glean, Ally and Crusader at the PSPE timing should be avoided due to the significant yield loss measured in this trial.
Despite the lack of registration, the use of Group B sulfonyl urea chemicals like Ally, Glean and Logran prior to seeding did not result in a decrease in yield.
All Group B chemicals do not have activity on weeds such as, prickly lettuce and milk thistle on NYP, so it is recommended that a tank mix partner be added to assist with the control of these problematic weeds.

Acknowlegement

Leighton Wilksch, Lynton and Avan Ireland, NSS Committee and NYNRM

Contact details

Chris Davey

YP AG, 2 Kennett Street, KADINA SA 5554

chris@ypag.com.au

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