Weekly Report 5/27/2025

This is the fourth post of the 2025 season for the Tree Fruit Pest Monitoring Network. Each week we’ll provide a short summary of trap captures and pest activity in orchards from across NY State. Look for more detail and regionally specific management recommendations from your local CCE and regional teams.

Weather and Phenology across the state now

Orchards in NY are at petal fall and sizing. In Highland at the Cornell AgriTech Hudson Valley Research Lab, reference McIntosh block was near 10-15 mm fruitlet diameter on Monday 5/26. In Geneva at Cornell AgriTech, apples are sizing as well. Average petal fall date in Geneva is , standard deviation of 6 days. In the Champlain Valley and Lake Ontario, orchards are at petal fall and fruit set, with fruit slowly sizing. There appears to be a good fruit set in most of the state at this point in time, with plenty of time yet in the season.

The past week was quite cool, slowing down both phenology and pest activity, and making thinning conditions a bit challenging. High temperatures only reaching into the 50’s (F) in WNY and CV, and the low 60’s in the HV, and degree day accumulation was only 50-60 DD43 (compared to 100-150 DD43 the previous week!). It has been extremely wet for most of the month of May. Average precipitation for May in most of the state is between 3-5″, and in May this season, NEWA stations have recorded over 7″ at many weather stations in the Hudson Valley, and 5 or more in most of the rest of the state. Forecasts indicate we’ll have a few dry days with potentially 1/2″ or more Wednesday-Thursday this week. This will likely be followed by dryer and warmer than average temperatures in the coming two weeks, according to the NOAA climate prediction center.

Approximate apple phenological stages recorded in locations across NY State 

Record these biofixes for your orchard!

Phenology & DDs for NY NEWA Stations from 1/1 – 5/26

*all DDs Baskerville-Emin, B.E

Upcoming Pest Events

Fact sheets for tree fruit pests can be found on the Cornell IPM Fact Sheet website. More information on the NEWA Models can be found on the NEWA website and in this NEWA Quick Guide for Apple Insect Pests. 

Diseases

Apple Scab primary infection season is over in most of the state, you can check the NEWA scab model for predicted end of primary season. It is a good idea to stay covered for a couple of extra weeks, particularly if there is any risk that primary scab was not fully controlled and secondary spores (conidia) may be present. Now is also a great time to start scouting for early scab infections that may have occurred, lesions take at least 2 weeks to begin appearing. Lesions will take longer to develop in cooler weather, such as this year. Look for olive green to brown lesions, on the oldest leaves first, often first appearing on the underside of the leaves.

Fire blight is a very low risk due to the cold weather and most orchards being beyond bloom. But this could change if we move into 80F temperatures next week, where blossoms are open (including some ‘rat tail bloom’, newly planted trees, and late varieties). Use the NEWA fire blight model to determine if there is risk in your orchard. Temperatures must been sufficient for growth of the bacteria on the flowers, followed by ample rain and humidity needed to produce an infection event. The first symptoms of blossom blight are now evident in a few inoculated and untreated blocks. Look for wilted flower clusters with blackened fruit petioles (stems) and stuck to the cluster, compared to thinning activity, which turns yellow and falls off the tree. Ooze will also be evident once there are warmer conditions and more bacterial growth.

Powdery mildew is very active throughout the state. This is despite the ample rainfall, which can suppress the disease, as the pathogen cannot survive in free water. The first infections take place on new developing shoots and flower clusters, after emerging from buds, where the pathogen overwinters; fruitlets are contorted and turn brown and fall off the tree. This is followed by secondary infections, visible as powdery white sporulation on new shoot terminals. Management for this disease should begin around second cover. Check out this article summarizing seasonal powdery mildew recommendations. https://blogs.cornell.edu/enychp/tree-fruit/apples/powdery-mildew-management-review-for-2025/

Rust diseases are very active now across the state, thriving in the ample rainfall. We observed the first small, circular, bright orange lesions on apple leaves this week and late last week. This disease is active at about the same timing as scab, in that infections occur early in the season, and then become inactive. Lesions are found on the top surface of leaves, with pycnia emerging from the underside of leaves.

Black Rot or Frogeye Leaf Spot is also active now in most of the state. Black rot overwinters as mummies in the canopy and in damaged or diseased woody tissue. Spores in the spring, typically during bloom, infect new shoot tissue, then later fruit tissue. Look for round purple to brown spots on the leaves. Other pathogens may take advantage of these lesions, causing them to coalesce and merge together. We are observing abundant foliar lesions in low managed orchard in the Hudson Valley, where there has been plenty of opportunity for infection and disease development with all the rainfall.

Leaf spotting has been observed and reported in many locations. Many different biotic and abiotic causes may be responsible for leaf spot symptoms. Marssonina and glomerella (bitter rot) are both active at this time and cover sprays should start soon for these diseases. In addition, symptoms have been observed from many abiotic causes, including yellowing due to excessive moisture and/or poor nutrition, chemical injury, and mechanical damage have all been seen. It is critical to properly diagnose the damage observed to ensure effective management.

Insects

Now is the time of year to be checking traps and recording the first biofixes for economically significant insects. A biofix is a biological indicator, observed in the field/orchard, used to start model calculations. Many models use a unique biofix, which must be recorded at the particular location of interest. Examples include 50% green tip, first sustained trap capture of moths (e.g. 2 consecutive weeks of adult captures). Specific biofixes used in NEWA can be found online: https://newa.cornell.edu/default–biofix–dates/. 

Plum Curculio damage has been observed on developing fruitlets in the Hudson Valley. Fruitlets become susceptible once they reach approximately 4-5mm in diameter. Adults typically become active after a few nights with temperatures of 55-60 degrees F, and move into orchards from hedgerows. Management typically begins at petal fall. Coverage should be maintained up to 308 DD Base 50 after petal fall. Use the NEWA PC Model to determine when you’ve reached the 308 DD Threshold.

Oriental Fruit Moth biofix as been recorded in many locations throughout the state. Tunneling and frass has been observed in developing fruitlets in unmanaged blocks in the Hudson Valley. If you have had a past history of damage and trap catches are high (>10/trap/week), specific management is recommended. Use the NEWA OFM Model to forecast when egg hatch will occur and time insecticides. Management typically coincides with petal fall and other insect management at this critical timing. An additional cover is recommended approximately 10-14 days after the petal fall application. These caterpillars can cause damage to stone fruit in which adults lay eggs near fruit buds in fall of the previous season, then the first generation emerges and tunnels into terminals, causing flagging of terminals. In apples, OFM will tunnel into fruitlets, similar to codling moth, but does not feed on seeds.

Management timing:

• 170-200 DD 45, hatch of first generation larvae around petal fall
• 1150-1200 DD 45, hatch of second generation (after first gen biofix), approx. late June

Codling Moth first trap captures have been recorded in both the Hudson Valley and Geneva. Traps should be placed at approximately bloom to monitoring first adult flight. Then use the NEWA CM Model to predict when egg hatch will occur an when to time insecticide, after first ‘sustained’ trap capture (i.e. two weeks of consecutive trap captures) has been recorded.

Management timing for insecticides:

• Insecticides targeting eggs: 150–175 DD 50 after biofix (note, Rimon may only be used once per season in NYS)
• Insecticides targeting hatching larvae: 230–250 DD 50 after biofix
• Follow up 14 days later

Rosy apple aphids and green peach aphids are very active in orchards now. RAA typically colonize fruit clusters, causing distorted tissue; make sure to flip leaves over to inspect for colonies. Green aphids are typically active on the newest terminal leaves first, also flip leaves over to look for colonies or winged adults.

Lesser Apple Worm is also active around the state. It is a minor fruit pest, but frequently captured in OFM traps. These moths may be slightly smaller and have a more defined, metallic wing pattern, compared to the dusty brown appearance of OFM.

Spongy Moth was also observed over the past few weeks in the Hudson Valley, but populations seem to have declined in orchards. This is an uncommon pest of tree fruit, but in past seasons (including 2024) populations were significant enough in many locations to cause damage to leaf and even fruit tissue. People handling fruit or working in the orchard may also have an allergic reaction to the insects. Webinar on spongy moth from Cornell First Friday series: https://youtu.be/G21PGVT2k4w?si=eLefn8ZlS-HXSqXf 

Tarnished Plant Bug has been observed in high numbers in most of the state. These true bugs have piercing sucking mouthparts that they insert into the new flower buds to feed. You will find the insects or droplets of sap (clear or amber in color). White sticky cards can be used to monitor for these insects, placed along the border of plantings, where insects are emerging from overwintering sites in hedgerows. Recommended action threshold for management is an average of 3 TPB/trap over 5 traps. Typically active and feeding on fruit buds through pink and early petal fall.

European apple sawfly is active a this time as well. Typically around petal fall, the first instar larvae will feed just under the surface of the skin of the fruit, leaving a spiral scar around the fruit. These wounds are evident now in orchards in the Hudson Valley.

Obliquebanded Leafroller overwintering larvae are present in many orchards. Look for very small green caterpillars in flower clusters and terminal leaves. You may see frass, feeding, and webbing together of leaf and floral tissue. Trapping for adult flight of the first seasonal population will begin around petal fall. Monitoring for this generation will occur later in the season, late June to early July.

Black Stem Borer has become very active in the Hudson Valley. Activity has been observed for the past few weeks in EtOH soaked bolts. Pay particular attention to trees with stress, including drought, too much water in the soil, winter damage. Look for toothpick or sawdust frass in the lower part so the trunk, with small round entry holes.

Apple leafcurling midge first trap captures were recorded across NY State at approximately tight cluster. The first leaf curling was observed in the Hudson Valley last week and again this week. This is an insect that sporadically causes damage in New York. Over the past few years we have received increasing reports of damage, particularly in isolated locations in Western NY and the Champlain Valley. Emergence is typically near TC, then rapid increase 3-4 generations per year in NY. Damage is evident a bit later, as tightly curled terminal leaves, curling inward rather than outward like leafhopper damage, and very brittle to the touch.

Dogwood borer typically becomes active in early June in Geneva. First trap capture was reported in the Hudson Valley last week, with no new captures this week. These are clear-winged moths with distinctive yellow banding. Flight of the adults and egg hatch lasts for a long period of the season, often up until harvest, making management targeting egg hatch difficult. Mating disruption is a very effective management strategy, now is a good time to be deploying mating disruption dispensers.

European red mite and Two Spotted Spider Mite infestations have been reported in the Hudson Valley. Typically the first scouting period for this insect is recommended in June. Use the diagrams in the Cornell Guidelines for sequential sampling methods and thresholds for management.

Upcoming Phenology & Pest Events Table

Reference: Table 7.1.4. Degree-day accumulations (from Jan. 1) corresponding to selected fruit phenology and arthropod pest events. Cornell Tree Fruit Guidelines.

Additional Resources

Weather

Northeast Regional Climate Change Monthly Maps
https://www.nrcc.cornell.edu/regional/monthly/monthly.html

NOAA Climate Prediction Center (forecasts and outlooks)
https://www.cpc.ncep.noaa.gov/products/forecasts/

NEWA and Pest Forecasting

NEWA Help Desk Frequently Asked Questions
https://help.nysipm.org/hc/en-us/categories/16994462926231-NEWA-Network-for-Environment-and-Weather-Applications

NEWA Help Desk Apple Insect, Disease, and Crop Management Forecasts
https://help.nysipm.org/hc/en-us/sections/17011505301783-Apple-Insect-Disease-and-Crop-Management-Forecasts

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

Apple IPM Intensive Workshop playlist:
https://www.youtube.com/playlist?list=PLoNb8lODb49vifrm9Tla4GmAVhlIL0527

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

Virtual Orchard Scout Training webinar recording on the New York State Integrated Pest Management Program (NYSIPM) YouTube channel.
https://www.youtube.com/watch?v=OtyOWCL1Q2A

Online Course, BF224: Tree Fruit Scouting.
https://smallfarmcourses.com/p/bf-224-tree-fruit-scouting