Difficult weather conditions continue
01 December 2016
Orchards in the Bay of Plenty and other regions have continued to be battered by strong winds over the past fortnight with cane loss and severe leaf damage, particularly in high altitude and/or wind exposed Hayward canopies. Elevated levels of Psa leaf spot and flower-bud infection are also being seen on these orchards as pollination continues. Leaf spotting has also been reported on a few Gold3 blocks.The increase in Psa symptoms is unsurprising given the high level of canopy damage, as wounds have created multiple access points for Psa. Growers are recommended to reapply copper cover as soon as pollination is complete to manage Psa inoculum levels and should consider additional coppers prior to periods of high risk weather throughout the balance of the growing season. Typically, Psa risk reduces significantly as temperatures rise to 20 degrees or above; however, growers with moderate or severe leaf spot are reminded that these spots continue to be a potential inoculum source when weather conditions favour Psa. Prune males during dry periods and follow up with protective sprays as soon as practicable to protect pruning wounds and recovering leaf canopy. Foliars to support leaf and vine recovery should be tailored to individual orchard needs. Maintain a five to seven-day gap between applications of foliars and copper to minimise the risk of phytotoxicity to leaves and fruit. Do not apply sprays in poor drying conditions or high humidity as risk of fruit staining increases. Be aware of fruit sensitive periods Gold skin sensitivity commences around 21 days after fruit set with risk increasing between 28 and 42 days and reducing again between 42 and 80 days. For Hayward, 14 to 35 days after fruit set is considered a high-risk period. If needed, protective sprays may be applied but take extra caution to ensure excellent spray conditions. Protective Psa programs should be continued on all sites with high levels of wind damage and leaf spot, irrespective of remaining fruit numbers. Failure to maintain a strong program risks inoculum build-up within the orchard and may also add risk to neighbouring orchards.