SOUTHWEST FLORIDA: Hidden from the headlines, citrus black spot (CBS), caused by Guignardia citricarpa, is back in the spotlight.

Groves where CBS is present are subject to stringent guidelines that increase production and harvesting costs. CBS also renders fruit unfit for fresh market sale because of the symptomatic black lesions caused by the disease. These factors, along with reduced access to key export markets and the need for increased fungicide use, reduce the profitability of groves.

Spread and management

Citrus groves are most susceptible to infection April through September, when precipitation rates are at their highest. Because CBS is spread by windborne ascospores present in both fallen leaf litter and in existing fruit lesions on the trees, the University of Florida recommends preventative measures to help reduce the spread of the disease.

Syngenta agronomists recommend that growers be proactive in making management decisions, and also:

• Utilize regular fungicide applications beginning in April and continuing on 30-day intervals through September
• Manage leaf litter in groves
• Limit movement of infected leaf litter from one grove area to another
• Remove weak or declining trees
• Enhance air movement and leaf drying
• Minimize dead wood in tree canopies
• Source clean nursery stock
• Sanitize equipment when moving fruit from one grove to another

For protection against CBS, growers can turn to Quadris Top® fungicide. The two active ingredients in Quadris Top, azoxystrobin and difenoconazole, are provide enhanced disease protection, while the two modes of action deliver resistance management benefits.

Take control

To optimize crop protection product performance and reduce the chances of resistance development, Syngenta agronomists suggest that growers:

• Apply full rates of fungicides
• Incorporate all proven effective modes of action
• Use no more than two sequential applications of any mode of action
• Incorporate other methods of disease suppression such as leaf litter management and increased airflow

A well-executed fungicide program, in conjunction with good cultural practices, can help Florida citrus growers reduce the spread of citrus black spot and decrease fruit drop. Incorporating these tactics into existing disease management programs will set growers up for a profitable season.

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Product performance assumes disease presence.

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