Research shows Psa causes Gold3 bud rot
A two-year study designed to fill knowledge gaps around Gold3 bud rot has identified Psa as the cause of infection.
Similar to Hayward, Psa infection was seen to start on the outside of Gold3 flower buds and then move inward to internal bud parts. Flower buds were susceptible to Psa infection from very early on; when they had just emerged, were swelling but still tightly closed, and had stalks which had not yet started to lengthen.
This research highlights the need for early spray protection to limit external inoculum before buds reach this growth stage. Psa could be found on apparently clean flower buds, with sepal browning not showing until 14 days after infection.
The project also monitored the incidence and progression of Gold3 bud rot and the effect of rootstock on prevalence of infection. One commercial and one research site were surveyed and significantly higher levels of bud rot were found on Gold3 -“Bounty 71” (2-35%) versus Gold3-Bruno (less than 1%).
The amount of infection differed between sites and seasons and was linked to rainfall, site inoculum levels and timing of protectant sprays. Bud rot symptoms on these Te Puke sites started to increase significantly from late October, suggesting infection had occurred early October.