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River Birch Defoliated by Caterpillars: Identify, Spray Now, Prevent Next Year

Current Outbreak

Massive caterpillar migration (audible frass rain) stripping leaves. No webs this year = not tent caterpillars. Likely yellownecked caterpillar (feeds gregariously on birch, oak, maple, etc.).

Immediate Action

Spray congregated caterpillars and trunks with Orthene (acephate)—contact kill.
Tree will refoliate next spring; one defoliation rarely kills hardwoods.

Prevention for Next Year

Early spring: soil drench Bayer Advanced Tree & Shrub Insect Control on only the trees damaged this year. Systemic protects new foliage all season.

Don’t Treat Everything

Caterpillars prefer certain species. Treating unaffected plants wastes money and harms beneficials.

Trees: River Birch Webbing: Spider Mites or Fall Webworms—Not Spiders; River Birch Surface Roots Near Building: Do Not Cut—Add Sand, Prune Limbs Instead; Velvet Galls on River Birch: Mite Damage, No Treatment Needed; River Birch for Southern Exposure in Ohio: Wind-Resistant & Fast-Growing; New River Birch Trees Slow to Leaf Out: Water, Don't Fertilize; Ice‑Damaged River Birch: When to Remove a Broken Trunk; Birch Defoliation by Caterpillars: To Spray or Not?; River Birch Worm Control: Sawfly Identification and Treatment; River Birch Near Driveway/Foundation: Use Dwarf Cultivar; River Birch (Betula nigra): The Four-Season Star for Difficult Sites

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