Multiple biological products will reduce fungal disease and increase yields for dwarf beans and peas, but further trial refinement and financial analysis is needed, according to latest results from a project trialling biological products in peas and dwarf beans.
The project involves A Lighter Touch, Process Vegetables NZ, processing companies, Heinz-Wattie’s (KraftHeinz) and McCain Foods, and research partner Bioeconomy Science Institute. It aims to identify biofungicides, biostimulants and synthetic products which are effective against two of key diseases, fusarium root rot in peas and sclerotinia sclerotiorum (white mould) in beans.
Root rot can reduce marketable pea yield by 10–30%, and sclerotinia can reduce pod yield by 10–15% and cause post-harvest damage. Currently, growers have only two fungicides available to use due to international market restrictions on maximum residue levels.
Dwarf bean crop. Credit Nigel Rowe-Lucas.
The third year of trials, in the 2024–2025 season, evaluated the best performing biological products from year one and two in peas and bean trials in Canterbury and in a Hawke’s Bay-based bean trial.
Year three trials aimed to identify effective options for 2025–2026 field trials as well as contributing data to support future label claims and/or registration of products, if the products evaluated were shown to be effective.
An analysis of the financial benefits of using biologicals in pea and bean production compared with conventional systems using synthetic products was identified as an area for future work.
The year three report also highlights the need to consider and understand compatibility of products with each other and with current registered products in order to integrate biologicals effectively into pea and bean crop protection programmes.
Farhat Shah and Monika Joshi, of Bioeconomy Science Institute (BSI), sampling plants for analysis from the 2024-2025 bean trial in Canterbury. Credit: BSI
As low sclerotinia disease pressure was a challenge in 2024-2025, the report identified better site selection was needed for future trials and additional irrigation pre, and mid-flowering would ensure disease development.
For the first time in the multi-year project, postharvest soil samples were analysed for pathogen loads, building knowledge about disease control. The 2024–2025 results are briefly summarised below:
The 2024–2025 pea trial
For peas, all products, including the fungicide control, reduced root rot severity and two products achieved a reduction above that of the fungicide control treatment.
Prolonged wetter and cooler conditions in December–February in Canterbury, and high root rot infection at site could have contributed to the significantly lower yields in this trial, with marketable pea yield on average almost a third lower than the 2023-4 trial.
Despite the poor yielding season, all products increased average pea yield by 8.5–24% when compared to the untreated control in the trial. Two products, a biostimulant and an off-label synthetic, increased yield close to that of the fungicide control.
The 2024-2025 bean trial
For beans, both sites produced a very high percentage of marketable quality pods. Warm and dry conditions were not conducive to disease development.
Sclerotinia infection started during early flowering and progressed over a longer period in Canterbury, but in Hawke’s Bay the delayed appearance of disease was possibly due to weather conditions and disease pressure differences between locations.
Product performance to reduce disease varied at the two sites, with lower reductions for the Hawke’s Bay trial due to lower disease pressure.
One product incorporated into the soil pre-sowing, reduced disease severity in both locations, and decreased and killed the sclerotia (dormant resting structure of fungi) in the soil after crop harvest.
Pod yield increased with several different products at both sites and in the Hawke’s Bay trial, all products increased residue fresh weight compared to untreated control.
Overall, the year three trials confirmed promising results seen in previous years trials, and highlighted opportunities for further insights into the financial implications of use of biological treatments compared to conventional products.
The 2025–26 season trials for the project have now been completed, with trial results expected to be available later this year.
Find out more about previous work on this project here.
