See recommendations on Algal Spot treatment for Florida citrus growers from the UF/IFAS Tip of the Week.

Algal Spot was in abundance last summer, so it’s likely to be an issue this year as well. The UF/IFAS Tip of the Week, published in a Citrus Industry article, maintains that algal spot is a disease caused by algae that appears as gray-green colored rings or donuts that turn a noticeable bright rusty red color in mid-summer. According to the article, “lesions can crack and crumble bark, stunt limbs and kill branches up to 2 inches in diameter.” The tip also shares algal spot treatment recommendations based on recent research. See the details below.

Algal Spot Treatment Options

Laura Dewdney, a UF/IFAS associate professor and the author of the Tip of the Week, shared that “three applications of 0.5 gallons per acre of a phosphite salt with a fungicide label are recommended.” The timing for the treatments, according the article is:

1) dormant spray (late January and mid-February),

2) post-bloom (late April to mid-May)

3) while algae are fruiting and red (June and July)

Dewdney also shared that recent research seemed to indicate that “three applications of ProPhyt (3x) had equivalent activity on the fruiting of the algae to a program of the two later applications (ProPhyt 2x).” However, a further year of the trial, which has only run for two years, would yield results that can lead to reliable recommendations.

Regardless of whether growers utilize two or three applications, the article maintains that “ProPhyt treatments reduced the severity of symptoms, including bark cracking.”

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