Bayer CropScience’s Gem fungicide available to control citrus black spot

Bayer CropScience has issued a 2(ee) recommendation in Florida for Gem fungicide against citrus black spot, a devastating disease that blemishes fruit with hard lesions and reduces yield due to premature fruit drop.

USDA and APHIS scientists confirmed the first U.S. occurrence of the disease in Collier County March 8, 2010. Citrus black spot, caused by Guignardia citricarpa, is reportedly the most significant citrus disease in Brazil, infecting 80 percent of citrus acres. Spores are spread primarily by wind and rain and from infected plant tissue.

Herb Young, fungicide product manager with Bayer CropScience, believes Florida citrus growers have the determination and the tools to manage the disease.

"Our Brazilian colleagues have dealt successfully with citrus black spot for several years," Young said. "And we know from their experience that Gem is a top performer against this pathogen."

Young explains that Gem locks into the waxy outer layer of fruit and leaves to form a barrier of protection. Small amounts of moisture create a vapor effect that helps to distribute the active ingredient more consistently throughout the plant canopy for complete and long-lasting protection.

"Waxy citrus cuticle really demands a fungicide that can stay with it," said Young. "This is a characteristic unique to GEM."

Under the 2(ee) recommendation, Gem 25WG may be applied at 4 to 8 oz/A with a seasonal limit of 32 ounces. For resistance management, do not make more than four applications of Gem or other strobilurin-class fungicides per season and no more than three sequential applications. Gem may be applied up to 7 days prior to harvest and is also labeled for melanose, scab, greasy spot, Alternaria and post-bloom fruit drop.