Phyllosticta Leaf Spot

Phyllosticta spp.

45 host plants · Fungal

Last updated

Data Maturity Baseline

This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.

On maple leaves you'll see discrete, angular brown or black spots appearing by late spring or early summer, concentrated on older foliage first. These spots have well-defined margins and don't typically form the explosive merging pattern seen in some other leaf spots. Wet weather in spring and early summer accelerates symptom development, and overhead watering creates ideal conditions for the fungus to spread through splash and spore dispersal.

Phyllosticta leaf spot on maples is rarely life-threatening but causes premature defoliation that weakens the tree and reduces its vigor. The fungus overwinters on fallen leaves, so your most effective strategy is sanitation: rake and destroy all fallen leaves in autumn before spring spore release. Avoid overhead irrigation whenever possible, and if you must irrigate, water early in the morning so foliage dries quickly. Good air circulation through pruning helps tremendously in humid climates.

Quick Reference

Agent Type
fungal
Causal Agent
Phyllosticta spp.
Host Plants
45
Spread
Rain splash and air currents dispersing spores from pycnidia
Favorable Conditions
Spring; cool wet conditions (50-65°F) with 8+ hours continuous leaf wetness. ...

Management

Vulnerability Window

Early spring (BBCH 12-16: leaf expansion). Young, tender foliage most susceptible. Peak infection window: late March through May.

What Triggers Infection

Spring; cool wet conditions (50-65°F) with 8+ hours continuous leaf wetness. Fungus (Phyllosticta spp.) requires moisture for spore germination and infection.

Cultural Controls

  • Rake and destroy fallen leaves.
  • Avoid overhead irrigation.
  • If overhead irrigation is necessary, water when foliage can dry quickly.
Regional Notes

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Host Plants (45)

Acer buergerianum Trident Maple, Three-toothed Maple Acer campestre Hedge Maple, Field Maple, Common Maple Acer capillipes Red Stripebark Maple, Red Snakebark Maple, Hakkoda Maple Acer carpinifolium Hornbeam Maple Acer circinatum Vine, Maple Acer coriaceifolium Leatherleaf Maple Acer crataegifolium Hawthorn, Maple Acer davidii David Maple, Père David's Maple Acer freemanii Freeman Maple, Hybrid Red Maple Acer ginnala Acer ginnala Acer glabrum Rocky Mountain Maple, Rock Maple, Douglas Maple, Dwarf Maple Acer glabrum var. douglasii Douglas Maple, Dwarf Maple, Rocky Mountain Maple Acer grandidentatum Bigtooth Maple, Western Mountain Sugar Maple, Rocky Mountain Sugar Maple Acer griseum Paperbark Maple Acer henryi Henry's Maple Acer japonicum Fullmoon Maple Acer macrophyllum Bigleaf Maple Acer maximowiczianum Nikko Maple Acer miyabei Miyabe Maple Acer monspessulanum Montpellier Maple Acer negundo Boxelder Manitoba Maple, Ash-leaved Maple Acer nipponicum Nippon Maple Acer oblongum Evergreen Maple, Smooth Leaf Maple Acer oliverianum Oliver Maple Acer opalus subsp. obtusatum Bosnian Maple Acer palmatum Japanese Maple Acer palmatum var. dissectum Dissected Japanese Maple Acer pensylvanicum Striped Maple, Moosewood Maple Acer pentaphyllum Acer pentaphyllum (no common name) Acer pictum Painted Maple Acer platanoides Norway Maple Acer pseudoplatanus Planetree Maple, Sycamore, Maple Acer rubrum Red Maple Acer rufinerve Redvein Maple, Honshu Maple Acer saccharinum Silver Maple Acer saccharum Sugar Maple Acer sempervirens Cretan Maple Acer shirasawanum Shirasawa Maple Acer spicatum Mountain Maple, Moose Maple Acer tataricum Tatarian Maple, Tartarian Maple Acer tataricum subsp. ginnala Amur Maple Acer tegmentosum Manchurian Stripebark Maple, Manchustriped Maple Acer triflorum Three Flowered Maple Acer truncatum Purpleblow Maple, Shantung Maple Acer velutinum Velvet Maple