DiseaseMedium Severity

Dothiorella (Elm Wilt)

Dothiorella ulmi

A fungal wilt disease affecting elm trees, particularly American elms. The pathogen causes yellowing, wilting, and gradual dieback through vascular disruption. Stress factors such as drought, malnutrition, and wounds significantly increase susceptibility to infection.

Peak Season: Spore release: Spring rainsPrimary infection: During wet weatherPycnidia development: Summer and autumnSecondary spread: Throughout growing season via irrigation and toolsOptimal conditions: Wet weather with overhead irrigation
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Dothiorella (elm wilt) showing characteristic yellowing foliage and vascular discoloration

Identification & Symptoms

What to Look For

Foliage yellowing and wilting in scattered crown portions
Generalized wilt spreading throughout the tree
Gradual dieback of affected branches
Brown discoloration in outer wood rings
Elliptical cankers on stems
Small black specks (pycnidia) in infected areas
Sticky spore masses around wounds in wet weather

Potential Damage

Vascular system disruption from vessel plugging
Progressive crown decline and dieback
Canker development around infection sites
Potential tree mortality in severe cases
Structural weakness from repeated infections

Lifecycle

Sticky spore masses on leaves and twigs are spread by wind, rain, overhead irrigation, and pruning tools. Infection usually occurs through leaf wounds but may enter through stem wounds. The fungus moves down leaf petioles into twigs, plugging vessels and creating cankers. New pycnidia develop during summer and autumn.

Professional Treatment Approach

1

Fungisol applications for vascular disease management

2

Address stress factors: improve drainage, reduce compaction

3

Proper pruning practices to minimize wounds

4

Avoid overhead irrigation where possible

5

Nutritional support programs to maintain tree vigor

Recommended Mauget Products

Fungisol

Professional-grade treatment specifically effective against dothiorella (elm wilt).

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