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Pest & Disease Library

Diagnostic entries for the pests, diseases and fungi you find in the field — symptoms, range, peak season, severity and treatment. Cross-linked to the species they attack, and feeding the regional alert map.

Tracking an outbreak? The alert map shows where each pest is active right now.Open the alert map
22 of 22 entries
Moderate
Anthracnose
Apiognomonia / Discula / Colletotrichum spp.
fungusPeak: Spring, during cool, wet, rainy weather at and just after leaf-out
Low
Aphids
Aphidoidea (various species)
pestPeak: Populations build in spring and early summer, with flushes through the season
Moderate
Apple Scab
Venturia inaequalis
fungusPeak: Primary infections in cool, wet spring weather (bud break through early summer)
High
Armillaria Root Rot
Armillaria spp.
fungusPeak: Decline visible in summer drought stress; honey mushrooms appear in fall
Severe
Asian Longhorned Beetle
Anoplophora glabripennis
pestPeak: Adults active and emerging July through October
High
Bacterial Leaf Scorch
Xylella fastidiosa
diseasePeak: Symptoms most visible mid-summer to fall (July–October)
Moderate
Bagworms
Thyridopteryx ephemeraeformis
pestPeak: Larvae feed and enlarge bags June–August; bags overwinter with eggs
High
Bronze Birch Borer
Agrilus anxius
pestPeak: Adults emerge and lay eggs late May through July; larvae tunnel under bark
Moderate
Cankerworm (Inchworm)
Alsophila pometaria / Paleacrita vernata
pestPeak: Larvae feed and defoliate in spring (April–May) as leaves expand
Moderate
Cytospora Canker
Cytospora / Leucostoma spp.
fungusPeak: Cankers expand in spring and fall; symptoms most visible in summer dieback
Severe
Dutch Elm Disease
Ophiostoma novo-ulmi
fungusPeak: Symptoms appear late spring through summer; bark beetle vectors active spring–fall
Severe
Emerald Ash Borer
Agrilus planipennis
pestPeak: Adults fly and lay eggs late May through August; larvae feed under bark spring–fall
High
Fire Blight
Erwinia amylovora
diseasePeak: Bloom through early summer, during warm, wet, humid weather
Severe
Hemlock Woolly Adelgid
Adelges tsugae
pestPeak: Woolly masses most visible fall through spring; two generations feed Oct–June
Severe
Oak Wilt
Bretziella fagacearum
fungusPeak: Spring and early summer (high infection risk from fresh wounds April–July)
Low
Powdery Mildew
Erysiphe / Podosphaera / Phyllactinia spp.
fungusPeak: Late spring through fall, worst in humid, shaded, crowded conditions
Moderate
Scale Insects
Coccoidea (various species)
pestPeak: Vulnerable mobile 'crawlers' emerge late spring–summer (species dependent)
Severe
Southern Pine Beetle (Pine Bark Beetle)
Dendroctonus frontalis
pestPeak: Multiple generations spring through fall; outbreaks peak in summer droughts
High
Spongy Moth (formerly Gypsy Moth)
Lymantria dispar
pestPeak: Caterpillars feed and defoliate May–June; egg masses laid mid-summer overwinter
High
Spotted Lanternfly
Lycorma delicatula
pestPeak: Nymphs spring–summer; conspicuous winged adults July–November; eggs overwinter
High
Thousand Cankers Disease
Geosmithia morbida (vectored by Pityophthorus juglandis)
fungusPeak: Beetles active and galleries expand spring through fall; dieback shows in summer
High
Verticillium Wilt
Verticillium dahliae / Verticillium albo-atrum
fungusPeak: Symptoms appear in summer, often after heat or drought stress (June–September)
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