14 April 2026 - Reminders for Early Season, Higher Risk for Apple Scab

This week on Scaffolds, I give some reminders to think about as the season starts, Kerik talks scab predictions, and Anna gives us our weekly state of the state update on degree day accumulations around the state.

Kerik: Apple Scab Disease forecast predictions for New York as of 4-12-26: There’s a lot of variability for Apple Scab risk across the regions. Eastern NY and the capital district have an easy week with few wetting periods and low levels of ejection. The lake champlain region may not all be at green tip. Western NY and the fingerlakes have accelerated apple scab maturity and prolonged wetting periods that span the week with high risk. In this region, the average temperatures during wetting periods are low 60s and could lead to many infections.

State of the State

Historical Phenology and Average Degree Day Accumulation Base 43 (for reference)

- Tight cluster (McIntosh) || 228 ± 27 || 27-Apr ± 7 days

- Pink (McIntosh) || 289 ± 26 || 3-May ± 7 days

- Full bloom (McIntosh) || 378 ± 35 || 10-May ± 6 days

- Petal fall (McIntosh) || 479 ± 42 || 18-May ± 6 days

Phenology & DDs for NY NEWA Stations from 1/1 – 4/13

Station || Stage || DD 43F || DD 43 Forecast Through 4/19 ||

Geneva || 1/2" green || 249 || 364

Highland (HVRL) || tight cluster || 257 || 404

Clifton Park || green tip || 178 || 301

Peru (Forrence) || first green || 114 || 193

Medina (Roberts) - Inland || 1/2" green || 214 || 306

Appleton North - Lake || 1/2" green || 148 || 207

Fairville (The Apple Shed) - Inland || 1/2" green || 235 || 334

Williamson (DeMarree) - Lake || 1/2" green || 180 || 254

*all DDs Baskerville-Emin, B.E

Upcoming Pest Events

Pest/Phenology Event || DD Base 43˚F || Approx. Date

STLM Traps set out || 1-Apr

Pear psylla – egg laying || 84 ± 44 || 33 ± 21 || 4-Apr ± 11 days

RBLR – 1st catch || 144 ± 32 || 60 ± 20 || 17-Apr ± 9 days

Rosy apple aphid – 1st nymphs present || 189 ± 55 || 86 ± 30 || 25-Apr ± 7 days

STLM – 1st adult catch || 168 ± 48 || 73 ± 28 || 20-Apr ± 9 days

STLM – 1st egg observed || 208 ± 65 || 94 ± 36 || 27-Apr ± 5 days

---

Tight cluster (McIntosh) || 228 ± 27 || 105 ± 19 || 27-Apr ± 7 days

Tarnished plant bug – 1st observed || 222 ± 105 || 105 ± 62 || 25-Apr ± 15 days

OBLR – 1st overwintered larvae observed || 236 ± 78 || 112 ± 48 || 29-Apr ± 7 days

Black stem borer – 1st adult catch || 283 ± 50 || 137 ± 40 || 6-May ± 3 days

European red mite – egg hatch observed || 284 ± 53 || 134 ± 34 || 6-May ± 4 days

---

Pink (McIntosh) || 289 ± 26 || 139 ± 21 || 3-May ± 7 days

OFM Traps set out || Pink

Oriental fruit moth – 1st adult catch || 229* ± 44* || 126 ± 33 || 2-May ± 8 days

RBLR – 1st flight peak || 303 ± 75 || 150 ± 48 || 4-May ± 9 days

STLM – 1st flight peak || 337 ± 71 || 168 ± 45 || 7-May ± 8 days

---

Full bloom (McIntosh) || 378 ± 35 || 192 ± 25 || 10-May ± 6 days

OBLR Overwintered Gen. Sample || Bloom

Codling Moth Traps set out || Bloom

Cold Temperature and Frost Risk

Picture Table of Critical Spring Temperatures for Tree Fruit Bud Development Stages https://www.canr.msu.edu/resources/picture-table-critical-spring-temperatures-for-tree-fruit-bud-development-stages

Regional Weather Events page for NEWA weather stations, including a map of freeze events on 4/25 and 26. https://newa.cornell.edu/regional-weather-events/

Cornell Statewide Frost Protection webinar held on Friday April 12th recording now available online here: https://youtu.be/TIBEpfb98ws

Scouting and Monitoring Resources

Video: Apple Insect Targets and IPM Practices (including explanations of Degree Day calculations), https://youtu.be/NwyBAcvbpUs

NY Tree Fruit Pest Monitoring Network Blog

https://blogs.cornell.edu/treefruitpests/

Interested in collaborating and contributing trap capture data? Contact Anna Wallis aew232@cornell.edu

Quick Guide for Apple Insect Pests https://help.nysipm.org/hc/en-us/articles/23290226665751-NEWA-Quick-Guide-for-Apple-Insect-Pests