Follow-Up: Professional Diagnosis Needed for Apple Tree Deaths
Two 2-year-old apple trees (Winesap, Golden Delicious) died with split bark, discolored branches, no bud break. A 7-year-old Fuji thrives nearby. The grower seeks both diagnosis and a spray schedule for fire blight and codling moth on the remaining tree.
Diagnosis: Why Extension Examination Is Critical
- Loose/split bark at base suggests crown rot, winter injury, or borer girdling.
- Discolored branches could indicate vascular disease or root failure.
- Without seeing roots and crown tissue, diagnosis is speculative.
- County Extension "house calls" are invaluable—they examine roots, soil, and can send samples to plant disease clinic.
Fire Blight Management for Fuji (Detailed)
Antibiotic Use (Agristrep/Streptomycin)
- Timing is everything: Apply at first bloom (10-20% open), repeat every 4-5 days through full petal fall.
- Coverage: Must wet all blossoms—use high-pressure sprayer, calibrate for tree size.
- Weather trigger: Models like Maryblyt or CougarBlight predict infection risk (temp >65°F + rain/dew).
- Resistance management: Never use streptomycin after petal fall. Limit to 3-4 applications/season.
- Fruit present? Label restriction: "Do not apply after fruit set." If flowers and fruit coexist, stop antibiotics and rely on biologicals/copper.
Integrated Fire Blight Program
- Dormant: Prune out cankers 12" below margin. Copper spray if history severe.
- Bloom: Serenade Opti (B. subtilis) every 4-5 days + BlightBan A506 if available.
- Petal fall: Fixed copper (Kocide, Champ) if warm/wet forecast.
- Summer: Apogee (prohexadione) at 1-3" shoot growth—reduces susceptibility.
- Sanitation: Remove strikes immediately, cutting 12-18" below. Disinfect tools.
Codling Moth Management
Degree-Day Timing (Essential)
- Biofix = first sustained moth catch in pheromone trap.
- 1st generation egg hatch = 250 DD (base 50°F) after biofix.
- 2nd generation = 1250 DD after biofix.
Organic Spray Options (Timed to Egg Hatch)
- CpGV (Cyd-X): Virus specific to codling moth. Apply at 250 DD, repeat 7-10 days later.
- Spinosad (Entrust): At 250 DD and 10-14 days later. Max 3 applications/season.
- Surround WP (kaolin): Apply at petal fall, reapply after rain. Deters egg-laying.
- Pyrethrin (PyGanic): Short residual, apply at egg hatch. Harmful to bees—evening only.
Non-Chemical Tactics
- Trunk banding (corrugated cardboard) for larvae crawling down to pupate.
- Prompt removal of infested fruit (drops and stings).
- Encourage woodpeckers, trichogramma wasps, bats.
Action Items
- Contact your county Extension office for a site visit (they'll diagnose the dead trees).
- Get a pheromone trap and degree-day calculator for codling moth timing.
- Purchase Serenade, Cyd-X, Entrust, Surround, and fixed copper for the season.
- Follow the label—it's the law and the science.
Your county Extension agent is your best resource for a localized, current spray schedule. They know the pest pressure, weather patterns, and variety specifics for your exact location.
