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United States Department of Agriculture

Agricultural Research Service

Title: Seasonal Responses in the Time it Takes for Camellia Twig Blight Symptoms to Develop

Authors
item Copes, Warren
item Thomson, Jessica

Submitted to: Southern Nursery Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 15, 2007
Publication Date: January 20, 2008
Citation: Copes, W.E., Thomson, J.L. 2008. Seasonal Responses in the Time it Takes for Camellia Twig Blight Symptoms to Develop. Southern Nursery Association Research Conference. 52:13-15.

Interpretive Summary: Little is known about the seasonal differences in how many days it takes before camellia twigs infected with the fungus Colletotrichum gloeosporioides develop disease symptoms. The time when infected twigs appear healthy is called the incubation period. Individual twigs were wound inoculated monthly with the fungal pathogen on separate sets of container-grown Camellia sasanqua ‘Rosea’ plants over a 2 year period. Inoculated twigs were monitored every other day for the development of twig blight symptoms and temperature measurements were taken every 30 minutes. The median incubation period lengths for the spring, summer, fall, and winter months were 18, 23, 28, and 57 days, respectively. This information directly benefits research scientists, because it provides relative measurements that can be used to model disease development. Also, the information can be used by extension scientists in teaching the public that infection precedes the appearance of symptoms by 2 to 8 weeks, and controls have to be done before infection occurs.

Technical Abstract: Little is known about how long after infection by Colletotrichum gloeosporioides camellia twigs can appear healthy before disease symptoms become evident, which is termed the incubation period. Individual twigs were wound inoculated monthly on separate sets of container-grown Camellia sasanqua ‘Rosea’ plants over a 2 year period. Inoculated twigs were monitored every other day for the development of twig blight symptoms. Temperature was measured at 30 minute intervals for 2 years. Survival analysis methods were used to determine the influence of stem diameter and temperature, in the forms of a seasonal response and the monthly average of hours between 59 and 86°F per day, on the number of days from infection until twig blight symptoms appeared. The length of the incubation period was fairly uniform for camellia stems infected monthly from May to September. The median incubation period lengthened significantly when stems were infected during the fall and was longest when stems were infected during the winter. The median incubation period lengths for the spring, summer, fall, and winter months were 18, 23, 28, and 57 days, respectively. In comparison to winter months, spring, summer, and fall months were all associated with significantly higher risks for disease symptom appearance.

Last Modified: 10/1/2014
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