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Polyphagous shot hole borer (PSHB) and its fungus in South African vineyards

by | Jul 27, 2021 | Viticulture

Project number
US FR 20-01

Project leader
Prof. F. Roets

Institution
Department of Conservation Ecology, Stellenbosch University

Completion date

2022

EXECUTIVE SUMMARY

Objectives and Rationale
PSHB is a devastating pest that carries the wilt fungus Fusarium euwallaceae which can cause significant economic damage. This project aimed to characterise the pathogenicity of F. euwallaceae to grapevine and assess its effect on grapevine health in the Western Cape Province.

Methods
We tested the pathogenicity of the fungus on Vitis vinifera cvs. ‘Merlot’ and ‘Cabernet Sauvignon’ on the Nietvoorbij experimental farm in Stellenbosch using a modified inoculation technique that mimics beetle activity on more than 100 individual plants of each. The effect of the application of plant fertiliser on fungal growth was also determined.

Key Results
Lesion development around inoculation points in grapevine consisted of dark staining penetrating no more than 2 mm into the xylem. There was no significant difference in lesion development between the isolates and the controls. After 3 months no Fusarium isolates were successfully recovered from any of the inoculated vines.

Key Conclusion and Discussion
The fungus never presented any significant lesion development and after three months no further lesion development was observed, and the fungus could not be re-isolated, indicating that the fungus could not survive within these tissues for prolonged periods. The fungus, and therefore PSHB does not seem to pose any immediate threat to grapevines.

Take Home Message for Industry
PSHB, does not seem to pose any immediate threat to grapevine. However, in February 2022 we saw some attempted colonisation of PSHB in a grapevine orchard in Somerset West. Infestations such as these will need to be closely monitored to detect any deviations from its current status.

Final Report.pdf

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