Pecan Scab Disease: Fungal Management for Nut Quality

Annual Problem

Brenda's pecans turn black every year. Diagnosis: Pecan Scab (Cladosporium caryigenum) — most common/damaging pecan disease.

Disease Details

• Small olive-green to black spots on leaves, petioles, nut shucks
• Severe: attacks twigs, catkins (male flowers)
• Lesions merge → terminal dieback, catkin drop
• Young tissue most susceptible
• Early nut infection → drop, cracking, secondary fungi entry
• Pink mold (Trichothecium) invades scab lesions

Disease Cycle

• Overwinters on infected plant parts
• Spores release mid-April (post-budbreak)
• Spread: dew, rain splash, wind
• Germination: free moisture + 65-85°F
• Dry/hot weather suppresses

Management Strategy

Best: Resistant Varieties

• Cape Fear, Elliott, Gloria Grande, Owens

Sanitation

• Remove/destroy leaves and shucks in winter

Fungicide Program (Commercial Standard)

• Start at budbreak
• 2-3 sprays at 10-14 day intervals (critical period)
• Then 21-day intervals after leaf maturity/nut set
• Homeowner option: Thiophanate-methyl (follow label)

Feasibility Note

Full spray program "not very feasible for homeowners" — large trees, equipment needs. Resistant varieties + sanitation most practical for home orchards.