Dr Sean Marshall, a microbiologist with AgResearch at Lincoln, is part of a team including Emily Gerard and David Wright (also from AgResearch) plus Drs Phil Elmer, Stephen Hoyte, Kirsty Boyd-Wilson, and Pia Rhinelander investigating how the Plant & Food Research (PFR) and Zespri biocontrol agent works against Psa.
Psa, first detected in New Zealand in 2010, is a bacterium that can result in the death of kiwifruit vines. It causes leaf spotting, cane and leader dieback, flower infection and bud rot, cankers and, in extreme cases, vine death accompanied by the production of exudates (a rusty red liquid discharge).
Symptoms of Psa are usually expressed during spring and autumn with cooler temperatures, regular rain and high humidity. The disease can be spread via windborne pollen, strong winds and heavy rainfalls as well as by footwear, vehicles and orchard tools, animals and humans. The bacterium infects the plant through natural openings (e.g. stomata and leaf scars) and wounds.
Plant & Food Research scientists with support from Zespri and Kiwifruit Vine Health (KVH) recently identified a potential new biocontrol agent. Working together with PFR, David Wright is attempting to ‘scale it up’ – and get it ready to be applied in a safe, cost-effective and efficient manner. It’s feasible that once developed, the new formulation of the biocontrol agent could be sprayed in kiwifruit blocks using conventional airblast spray equipment.
But, firstly and because it’s a biological product requiring registration, Dr Marshall and colleagues are trying to understand its mode of action in reducing Psa disease development.
