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Strategies for Maximizing Grain Yield Potential in HRZ Cereal Crops

Plant Growth Regulators (PGRs) have been a product of interest in Victoria’s HRZ for some time now, they are currently registered for use in wheat, barley and oat crops in Victoria. PGRs work by inhibiting the plant hormone Gibberellin which regulates plant growth and stem elongation. There has been strong interest for PGR use in high yield potential areas of south west Victoria. Benefits can be seen in large biomass cereal crops with height and lodging reduction, improved harvest index and reduced grain losses. In some scenarios PGRs have been shown to slow crop maturity, which could be a useful tool for frost mitigation in early sown crops.


Recent wheat trial results from Southern Farming Systems (SFS) in 2019 have shown that with the right finish to the season there can be a standalone grain yield increase in wheat that is not the result of lodging reductions. Past trial results have shown that yield improvements do depend on the season conditions through spring and grain fill, as in dry finish years yields in wheat can be negatively impacted from the use of PGRs. Use of PGRs in barley has been regarded as consistently successful over several years now, especially with the ability to apply a PGR at GS37 as well as GS31 to improve peduncle strength and reduce head loss.

Figure 1. Height reduction observed in wheat treated with Moddus Evo at GS31 growth stage (Left) compared untreated wheat on the right.


Some of the current PGR products registered in Victoria are Moddus Evo (Syngenta) and Errex (Syngenta). Moddus evo is registered for use at GS31 in wheat, barley and oats and also for use at GS37 in barley. Errex is only to be used in wheat crops from GS25-31 and it is mainly used as a companion product for Moddus evo in some wheat scenarios.


Moddus evo is compatible with most fungicides which can be applied at the GS31 timing, however fungicides which do not require additional wetters are preferred. Likewise, some trace element formulations are compatible however caution should be exercised when adding broadleaf herbicides into the mix as there can be increased crop effects from more complex mixes. For the best return on investment PGRs are ideally to be applied in situations of high yield potential, when crops are not stressed nor limited by moisture and when nutrition is not a limiting factor.


If you are interested in PGR use in your crop please consult your Western AG agronomist. Please also contact your agronomist before applying any PGR in a mix with fungicide, herbicide or trace elements to confirm compatibility. For more information on ‘SFS 2019 PGR trial’ results please refer to their trial report which will be available in their 2019 results book.

Article produced by - Claudia Higgins, Western AG Hamilton/Willaura

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