June 19, 2025

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By Becky Wiepz and Dan Kielar

Station Updates

• We are nearing the end of the effective window for chemical thinners in apples. After fruit reach 20mm, hand thinning is the most effective tool for cropload management.
• Station staff are currently working on wildlife abatement in all perennial crops.

UW Madison/Extension Updates

• Managing Phomopsis Cane and Leaf Spot in Wisconsin Vineyards
• Apple Powdery Mildew in Wisconsin Orchards: What You Should Know
• Apple Fire Blight Shoot Blight Management for Wisconsin Growers

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Historic Growing Degree Day Comparison

Date 6/18	2021	2022	2023	2024	2025	20-year avg.
Base 50	646.5	467.5	552	620.5	476.5	536

Recent Weather at Peninsular Ag Research Station

Date	Max Temp(℉)	Min Temp(℉)	Max Wind Gust(mph)	Daily Rain Total(in)
6/12	65.8	52.3	15.0	0.01
6/13	55.6	47.7	19.9	0.05
6/14	62.2	50.2	16.1	0.01
6/15	67.5	54.7	11.2	0.0
6/16	74.7	53.6	16.1	0.0
6/17	82.6	63	28.4	0.0
6/18	72.3	57.7	42.3	0.0

Apples

Growth Stage: Fruitlets approaching 20mm
Seasonal Update: Plant Growth regulators are most effective for cropload management when fruitlets are small. Measure fruitlets in your orchard and utilize the carbohydrate thinning model from NEWA to plan your treatments.

Pest	Southern Door	Central Door	Northern Door	Notes
Tarnished Plant Bug	Present	Present	Present	Light pressure continues
Spotted Tentiform Leafminer	Low Pressure	Low Pressure	Low Pressure	End of Flight
Codling Moth	Adults Caught	Adults Caught	Adults Caught	Flight continues *see caption below
Oriental Fruit Moth	Adults Caught	Adults Caught	Adults Caught	Flight Continues
Plum Curculio	Low Pressure	Low Pressure	Low Pressure	Very Little Damage in Commercial blocks
Peach Tree Borer			First Catch

Disease	Southern Door	Central Door	Northern Door	Notes
Apple Scab	High Risk	High Risk	High Risk	Increased risk with increased leaf surface and rain. Check Apple Scab models on NEWA to time spray applications.
Fire Blight	Low Risk	Low Risk	Low Risk	End of bloom significantly decreases infection potential. See article above for shoot blight management.
Powdery Mildew			Some Strikes Noted

Cherries

Growth Stage: Initial fruit set
Seasonal Update: Fungicide should be applied before rain events as new leaves continue to expand. Insecticide should be applied for Plum Curculio now that fruit is out of the shuck. Gibberellic Acid applications should be applied soon to encourage return bloom. Review this article from MSU and the label on you GA product for details on rate and timing of applications.

Pest	Southern Door	Central Door	Northern Door	Notes
Plum Curculio	No Scarring	No Scarring	No Scarring	No scarring observed in commercial fields but adults are present.
Spotted Wing Drosophila			1 Adult Caught	Egg laying cannot occur until fruit is vulnerable. Check fruit progression using the model from Wisconet. Sturgeon Bay is about 70% of the way to vulnerable fruit (665/954 GDD39.2)

Disease	Southern Door	Central Door	Northern Door	Notes
Cherry Leaf Spot	High Risk	High Risk	High Risk	Risk increases with leaf area expansion and rain events

GRAPES

Growth Stage: E-L Growth Stage 16-18
Seasonal Update: Pre-Bloom and Bloom-time fungicides should be applied as appropriate for your cultivar.

Pest	Southern Door	Central Door	Northern Door	Notes
Japanese Beetles				None Caught at this time

Disease	Station	Notes
Grape Phomopsis	None observed
Phylloxera	None observed	monitor plants for galls on leaf undersides

Additional Resources

• Mustang Maxx Label Updated to 3day PHI for tart cherries
• Chlorpyrifos (lorsban) is not allowed on any fruit crops in Wisconsin
• Take Steps To Ensure That You’re Complying With the EPA Herbicide Strategy To Protect Threatened and Endangered Species