Smaller particles, better PSA protection

Widespread in New Zealand, PSA-V (Pseudomonas syringae pv. actinidiae), also known as kiwifruit vine canker, is a particular threat during autumn and winter, a time when vines can be vulnerable. For growers, and the country’s economy, managing that risk is important.

Steve Huxtable, Grochem Regional Manager North Island, Central & North, says growers ought to be focussed on the prevention of PSA and have a disciplined spray programme in place. “It’s well reported, and understood, in our industry, that PSA-V can invade vines and even lead to them dying-off.

Steve says, “you should use a preventative copper spray, four to 5 times during the critical period”. Firstly, spray as soon as you pick the kiwifruit, then at leaf drop, and at pruning - which exposes scars - and again at early budbreak. Any fresh wound, stomata, or any cuts make the vine vulnerable to infection. 

Nordox™ 75WG is a cuprous oxide is one of the most concentrated wettable granule copper fungicides. It has better retention and excellent rainfastness. It’s an industry mainstay.

With the smaller particles, (at around 1.2 microns) you get 60% more copper ions on the surface than you would with a copper hydroxide product. Nordox’s particle size is extremely fine, and these small particles stick very well to the surface of the treated vines, providing a slow-release source of copper, which is both active against fungi and bacteria and serves as a source of essential micronutrients.

Copper products were applied to canes and allowed to dry.  Simulated rainfall was then applied and copper retention measured on the canes after 25mm, 50mm, 75mm and 100mm rain.  Data clearly showed more copper deposited in the Nordox treatment at time of application and better retention after rainfall, for both Hayward (HW) and Hort 16A vines (16A).”

“To get good disease control, you’re relying on consistent coverage. Nordox isn’t systemic – it kills bacteria on contact. The ions travel into the bacteria and disrupt cell activity.”

Nordox has 75% active copper content. Other copper products can have as little as 29%. 

Steve says, rainfastness is also an important attribute. “When particles are smaller, they’re more difficult for the rain to dislodge.”

“Nordox is also BioGro approved and very user-friendly; practically dust-free, easy to measure and low hazard classification.

PSA can be dispersed by wind, rain, or water droplets (the spores are typically airborne), but also transmitted by accidental contamination from plant matter or even by orchard vehicles, tools or footwear. (For tools, it’s recommended that they be disinfected between vines.) Steve says all staff should be able to identify PSA-V and maintain high standards of orchard hygiene. “Regular monitoring is also important, especially if the weather is likely to encourage PSA-V.”

Nordox is made using recycled copper and a catalytic process which, Steve explains, makes it very pure. 

He says it should only be applied according to the label and not in damp or cold conditions, as that can impact drying. “Don’t forget, you need to ensure spray gear is accurately calibrated, to get the best result, and if a vine is visibly unhealthy it’s best to give it a miss.”

For more information on Nordox and other Grochem innovative products, visit your local horticultural specialist or visit grochem.com

™ Nordox is a trademark of Nordox AS, Norway