Pod drop caused by strong winds is one of the biggest challenges faced by South Australian lentil growers, who frequently report losses of up to 0.5 tonnes per hectare due to wind events prior to harvest.

Consequently, pod drop is a priority for consultant Sam Trengove of Trengove Consulting in his work with the GRDC investment “Development and extension to close the economic yield gap and maximise farming systems benefits from grain legume production in SA”, also referred to as the SA Grain Legume Project.

Mr Trengove is also focusing on disease management and fungicide options for lentils. He is running trials at sites in central and northern Yorke Peninsula, including Kulpara, Maitland, Tickera and Ward Hill.

He notes that lentils have been the dominant legume in these regions for more than 20 years. “The area planted to lentils is growing state-wide, but in these Yorke Peninsula regions they have been an important crop for some time,” he says.

“Accordingly, our trials are aimed at maintaining and improving productivity in light of high-intensity rotations.”

Lentil pod drop

Although pod retention and pod drop are high priorities for growers, Mr Trengove says it has been difficult to develop treatments that have a big impact.

The drier conditions associated with the El Niño event experienced in 2023 increased the instance of pod drop in some cases. “In seasons with good rainfall, you usually have thick canopies that are well-knitted-together and therefore protected from wind, making pod drop less of an issue,” he says.

“Lighter canopies associated with drier conditions can increase pod drop due to plants shaking more and knocking against neighbouring plants, heightening the need for treatments to deal with it.”

In the 2021 and 2022 Kulpara trials (medium-rainfall zone), Mr Trengove investigated strategies to alter lentil crop canopy structure, such as treatments that aim to increase canopy bulk and therefore improve canopy knitting. These include increased fertiliser and sowing rates, and a zero-row spacing concept (2022 only), where a percentage of the seed is spread pre-sowing to fill in the inter-row spaces. However, these treatments did not reduce pod loss in these trials.

In 2021, application of EnviroShield® (a polymer protector film designed to reduce pod shatter and seed loss in canola and other shatter-prone crops, including lentils) either at desiccation or 10 days prior reduced pod drop by an average of 27 per cent compared to the control treatment, which lost 163 kilograms/ha, measured on the ground.

Sam Trengove at his Maitland lentil trial site. Photo: GRDC

Despite reducing pod drop slightly, these treatments did not increase harvested yield, with the EnviroShield® treatment’s yield of 1.59t/ha not statistically different from the control at 1.65t/ha.

In the 2022 trial, there was no significant pod drop. Mr Trengove says this was likely due to above-average rainfall and an extended growing season, which favoured high growth and biomass and led to crop lodging and associated protection from wind.

One result of note in 2022 was the superior yield achieved with GIA Thunder , which produced 680kg/ha (18 per cent) more than the PBA Highland XT control treatment, highlighting the importance of variety selection in some scenarios.

A 2022 trial at Tickera (medium-low rainfall zone) investigated the effect of previous stubble height on lentil growth, canopy structure and pod drop. Although increasing the height of retained stubble resulted in increased lentil plant growth and height, this did not have any effect on lentil pod drop or grain yield.

As with the 2022 Kulpara trial, this could have been due to seasonal conditions, which were favourable for high rates of lentil growth resulting in larger canopies for all treatments. In an average or drier season, taller plants might be more susceptible to pod drop.

On the other hand, the interaction with taller stubble might provide some protection, which was being investigated again in 2023, with trials being harvested at the time of writing.

Fungicides effective in wetter seasons

Trials at Maitland looked at fungicide use to control Botrytis grey mould (BGM) in PBA Ace (moderately susceptible to BGM) and Ascochyta blight (AB) in PBA Hallmark XT (moderately resistant to moderately susceptible to AB) lentils.

In the 2021 disease trials, the drier conditions through August and September led to minimal occurrence of BGM and AB, and high yields were achieved with and without fungicide.

However, a combination of wet weather and a large crop canopy resulted in high levels of BGM infection in 2022. By early October, more than half of the untreated plot was infected, resulting in 68 per cent crop death by 22 November.

“We had huge responses to fungicide, especially for control of BGM,” Mr Trengove says. “Yields in untreated plots were less than half those of the best plots treated with fungicide.”

The key findings for the BGM trial included:

• treatments containing Group 7 (SDHI) fungicides, including Filan® (under permit PER82476), Miravis® Star and Aviator® Xpro®, were highly effective at controlling BGM, as were group 2 fungicide Sumisclex® and combination products of Group 3 and 11 fungicides (Veritas® Opti and Amistar® Xtra);
• these fungicides improved BGM control and grain yield compared with commonly used carbendazim (2.6t/ha); and
• Filan (under permit PER82476) produced the highest grain yield at 4.2t/ha, while the untreated crop was reduced to 1.5t/ha.

The results were less conclusive for AB, which was only present at low levels and did not affect grain yield. Products containing an SDHI active ingredient (Filan® used under permit PER82476, Miravis® Star and Aviator® Xpro®) provided the greatest level of AB control, but were not significantly better than chlorothalonil.

New herbicide-tolerant lentil varieties

Another Maitland trial in 2022 looked at the performance of new lentil varieties with novel herbicide tolerance. This included GIA Metro and GIA Sire compared with the popular imidazolinone-tolerant variety PBA Hurricane XT .

GIA Metro has improved tolerance to metribuzin when applied post-sowing pre-emergent (PSPE). Metribuzin can also be applied post-emergent to this tolerant variety in accordance with permit PER92810. GIA Metro also combines imidazolinone tolerance for the post-emergent use of Intercept®.

GIA Sire has improved tolerance to clopyralid soil residues from applications in previous crops, again combined with imidazolinone tolerance.

The trial involved application of variety-specific herbicide treatments, including Intercept®, diflufenican, Reflex® and metribuzin.

In particular, the inclusion of metribuzin applied post-emergent (under permit PER92810) provided excellent control of common sow thistle, the dominant weed at the site, increasing control to 97 per cent in GIA Metro .

Sow thistle has emerged as a problematic weed in many high-intensity lentil growing regions. Control in PBA Hurricane XT trials with existing herbicide options combining Reflex®, Intercept® and diflufenican ranged from 52 to 68 per cent. (Note: Intercept® and diflufenican do not claim sow thistle control in lentils.)

Mr Trengove says the research, which ran in 2023 and will continue in 2024, has drawn a lot of interest from growers.

“They’re keen to see how the trial treatments play out versus their own operations and how they can tweak their own strategies,” he says.

The SA Grain Legume Project, which is led by the South Australian Research and Development Institute, aims to address the current 40 per cent yield gap between average grain legume yields and water-limited yield potential and drive its closure through supporting growers with extension of best-practice grain legume agronomy.

More information: Sam Trengove, 0428 262 057, samtrenny34@hotmail.com; PIRSA Media, PIRSA.Media@sa.gov.au