Copper fungicide effective in reducing red needle cast severity under controlled conditions
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Formerly known as the Forest Research Institute, Scion has been a leader in research relating to forest health for over 50 years. The Rotorua-based Crown Research Institute continues to provide science that will protect all forests from damage caused by insect pests, pathogens and weeds. The information presented below arises from these research activities.
From Forest Health News 288, May 2019.
A soon to be published paper from Scion’s Forest Protection Team provides further evidence for the effectiveness of copper fungicide in controlling red needle cast (RNC), caused by Phytophthora pluvialis (Rolando, et al., 2019).
The effect of copper, applied as a foliar spray of cuprous oxide at a range of doses between 0 and 1.72 kg ha-1, was investigated in two controlled trials with potted plants and in an operational trial with mature radiata pine.
In all three trials, severity of RNC was assessed by counting and/or measuring lesions formed after artificial inoculation of whole potted plants or detached needles with zoospores of P. pluvialis.
Results from all trials showed that cuprous oxide was highly effective at reducing infection. There was a significant negative relationship between copper concentration and RNC severity. Severity of symptoms were significantly reduced at application rates equivalent to, or above, 0.65 kg ha-1, with foliar surface copper levels as low as 13 to 26 mg kg-1 of needle tissue preventing infection.
These results indicate that the industry standard application rate for the control of dothistroma needle blight of 0.86 kg ha-1 may also be effective for RNC. Results indicated that treatment efficacy would remain for approximately three months.
This study provides the foundation for the development of a cost-effective management tool for RNC. However, further research on the epidemiology of disease, optimisation of dose, spray timing and frequency of application is required before operational guidelines for chemical control can be fully developed. Research at Scion continues to focus on improving our understanding of these aspects.
Stuart Fraser, Scion
Rolando, C., Somchit, C., Bader, M. K. F., Fraser, S., & Williams, N. M. (in press). Can copper be used to treat foliar Phytophthora infections in Pinus radiata? Plant Disease.
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