Saturday, March 30, 2024

Psa in check after its winter surge

Avatar photo
Orchard management methods and a warmer spring have helped kiwifruit growers better contain a winter-borne Psa surge. A cooler, damper winter this year proved a challenge to growers as Psa levels elevated after two winters of relatively lower infection rates.
Reading Time: 2 minutes

Kiwifruit Vine Health chief executive Dr Barry O’Neil said the practice of girdling vines also proved to be a valuable tool to help reduce Psa infection.

Girdling involved making a small ring-bark wound to the vine, putting it under some stress that sent nutrients to the fruit rather than the plant’s root.

In the initial aftermath of the Psa infection in late 2010, girdling was thought to have contributed to infection rates.

However, O’Neil said the reduction in Psa on girdled vines reinforced KVH research that indicated a 20-50% reduction in infection rate.

“It does, however, have to be done properly and would not be done on stressed, infected vines.”

Challenged, low-lying and damper orchards had exhibited the greatest level of infections this year, resulting in significant increases in Psa exudate levels and cane collapse.

“But on the other side we have had a relatively dry and warm spring and the Green varieties, especially Hayward, have shown less Psa spotting.”

Exceptional flower levels this spring were also providing some compensation in vines with heavier Psa infection.

Kiwifruit Growers president Neil Trebilco said more growers were engaged in flower thinning this season to preserve the quality of fruit in quantity parameters.

“This season had a particularly good bud burst so flower bud numbers are very high. In some cases flower numbers are double what they want for Gold fruit.”

“This season had a particularly good bud burst so flower bud numbers are very high. In some cases flower numbers are double what they want for Gold fruit.”

Neil Trebilco

Kiwifruit Growers

It appeared vines that contracted Psa last season had escaped this year.

“Whether Hayward vines are developing a greater tolerance to it, it is hard to know.”

Rainfall in the western Bay of Plenty was about 25% behind its historical year to date average but Trebilco said it was still too early to say whether the predicted El Nino summer dry pattern would affect vines and fruit growth.

O’Neil said crop yields in the sector continued to look strong, thanks in part to greater grower attention to any Psa infections and being more proactive with practices including increased use of artificial pollination.

He confirmed there still remained only one Psa infection detection in Northland, at a Maungatapere orchard.

“KVH have been up twice to monitor orchards and at this stage cannot find any evidence of further infections.”

Total
0
Shares
People are also reading