Olive leaf spot: epidemiology and control
type: CreativeWork
description: The overall goal of this research was to improve the understanding of the environmental factors affecting development of olive leaf spot (OLS) in New Zealand olive groves and to develop strategies for the disease management. The effects of temperature, relative humidity (RR), leaf wetness and leaf age on conidium germination were investigated for Spilocaea oieagina, the causal organism of olive leaf spot. Detached leaves of five leaf ages (2, 4, 6, 8, and 10 weeks after emergence), six different temperatures (5, 10, 15, 20, 25, and 30°C), eight wetness periods (0, 6, 9, 12, 18, 24, 36, and 48 h), and three RR levels (60, 80 and 100%) were tested. Results showed that percentage germination decreased linearly in proportion to leaf age (P<0.00 1). Temperature significantly (P<0.001) affected conidium germination, with the effective range being 5 to 25°C and the optimum being 20°C. The rate of germ tube elongation followed a similar trend, with the optimum being 15°C. Formation of appressoria, when found, occurred 6 h after the first signs of germination and their frequency followed the same temperature trends with a maximum of 43% at 15°C and none formed at 25°C. The minimum leaf wetness periods for germination at 5, 10, 15, 20, and 25°C were 24, 12, 9, 9, and 12 h, respectively. Studies on the prepenetration and infection processes on olive leaves by S. oieagina, using scanning electron microscopy, showed that the penetration pegs allowed direct penetration of the cuticle, but could not penetrate the host through the trichomes. A study of the effects of temperature, leaf age, conidial concentration, continuous and interrupted leaf wetness periods and relative humidity (RR) during the dry periods on whole plants showed that OLS severity decreased (P<0.001) with increasing leaf age at the time of inoculation. The severity of OLS also increased as inoculum concentration increased from 1.0 X 102 to 2.5 X 105 conidia per mL at all five temperatures (5-25°C), with most lesi…
abstract: The overall goal of this research was to improve the understanding of the environmental factors affecting development of olive leaf spot (OLS) in New Zealand olive groves and to develop strategies for the disease management. The effects of temperature, relative humidity (RR), leaf wetness and leaf age on conidium germination were investigated for Spilocaea oieagina, the causal organism of olive leaf spot. Detached leaves of five leaf ages (2, 4, 6, 8, and 10 weeks after emergence), six different temperatures (5, 10, 15, 20, 25, and 30°C), eight wetness periods (0, 6, 9, 12, 18, 24, 36, and 48 h), and three RR levels (60, 80 and 100%) were tested. Results showed that percentage germination decreased linearly in proportion to leaf age (P<0.00 1). Temperature significantly (P<0.001) affected conidium germination, with the effective range being 5 to 25°C and the optimum being 20°C. The rate of germ tube elongation followed a similar trend, with the optimum being 15°C. Formation of appressoria, when found, occurred 6 h after the first signs of germination and their frequency followed the same temperature trends with a maximum of 43% at 15°C and none formed at 25°C. The minimum leaf wetness periods for germination at 5, 10, 15, 20, and 25°C were 24, 12, 9, 9, and 12 h, respectively. Studies on the prepenetration and infection processes on olive leaves by S. oieagina, using scanning electron microscopy, showed that the penetration pegs allowed direct penetration of the cuticle, but could not penetrate the host through the trichomes. A study of the effects of temperature, leaf age, conidial concentration, continuous and interrupted leaf wetness periods and relative humidity (RR) during the dry periods on whole plants showed that OLS severity decreased (P<0.001) with increasing leaf age at the time of inoculation. The severity of OLS also increased as inoculum concentration increased from 1.0 X 102 to 2.5 X 105 conidia per mL at all five temperatures (5-25°C), with most lesi…
author: Obanor, Friday O.
language: en
keywords: Peacock spot, Cycloconium oleagina, Fusicladium oleagina, Olea europaea, olive leaf spot, germination, infection, sporulation, fungicides, population diversity, epidemiology, disease control, relative humidity, Marsden::300303 Plant protection (pests, diseases and weeds), Marsden::270403 Plant pathology
date published: 2006
date modified: 2026-07-24T02:50:30Z
provider: Lincoln University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Lincoln University

PropertyValue
property ID: Handle
value: https://hdl.handle.net/10182/1516