Study on seasonal fluctuations of the fungus Alternaria alternata population, causal agent of Thomson Navel black rot disease in North of Iran
Subject Areas : Plant Pestsسید وحید علوی 1 * , پرسا تیموری 2
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Abstract :
Black rot, caused by Alternaria alternata (Fr.) Keissl., is one of the important pre and postharvest diseases on Thomson Navel orange fruits in East of Mazandaran. During two years 2010-2011, the experiment was done in two citrus orchards with previous record of the infected fruit drop, a 12-years old orchard of Thomson Navel trees on sour orange and an 8-years old orchard of Thomson Navel trees on citrange, with 10 kilometers distance between them in north of Sari. Diameter mean of 50 fruits were measured in each orchard at 10 days intervals from 20 May to 20 September. Stylar end of the fruits was rinsed with Lacto-Tween solution and collected. Total and germinated spores mean on the fruit stylar end was calculated for each orchard. Regression analysis was determined between meteorological and collected data by SAS statistical software. Year effect had a distinctive trait on the results and number of germinated spores was related to temperature and rainfall in first and second years, respectively. Maximum spores accumulation and germination is predictable when the ten days precipitation average reach to more than three millimetre and the temperature mean more than 22 degrees centigrade, based on the results and the maximum infected fruit drop record in summer. This is optimum time for control of the disease.