Earlier production of ascospores and slightly more favorable conditions in Immokalee make the disease more severe there than in Central Florida. Because of the long infection period which now occurs, more sprays are likely to be needed to control the disease. In 1998-99, we conducted spray timing trials using single copper sprays in April, May, June, July, and August in Ft. Pierce, LaBelle, and Lake Alfred. Wetting of leaves by rainfall or irrigation triggers release of ascospores within 20-30 minutes.
High humidity can also cause release of small numbers of spores.
Once the pseudothecia are mature, many of the ascospores are released after the first wetting period with smaller numbers in the next 3-4 wetting periods. Subsequently, that leaf ceases to produce spores. In addition, we are evaluating the frequency and duration of wetting periods on pseudothecia and ascospore formation. Generally, it requires about 40 days of wetting and drying of leaves before ascospores are produced, but that varies with wetting periods. Epiphytic mycelial growth of Mycosphaerella citri on citrus and its control with fenbuconazole.