Spots on pear leaves are easiest to diagnose by color. Most problems that mark pear leaves start with a distinctive color and pattern, so a close look tells you most of what you need. Bright orange is the most common question we get, and it nearly always means one disease: pear trellis rust.

Table of Contents

The short answer: bright yellow-orange spots up to about an inch across, sometimes with tiny black dots in the center and growths on the underside, are pear trellis rust. It is a fungus that alternates between pears and junipers (WSU Hortsense). Pale green to reddish blisters that later turn brown or black are pearleaf blister mite. Small purple-black spots that grow into brown circles are Fabraea leaf spot (Penn State Extension). Leaves and shoot tips that suddenly turn black, as if scorched, point to fire blight.

The color chart

Color and pattern	Most likely cause	Season
Bright yellow to orange spots, up to 1 inch, black dots in center	Pear trellis rust	Spring to late summer
Pale green to reddish raised blisters, ⅛ to ¼ inch	Pearleaf blister mite	Spring, turning brown or black in summer
Small purple dots growing into purplish-black or brown spots	Fabraea leaf spot	Early summer on, worse in wet years
Whole leaves and shoot tips black and wilted	Fire blight	Bloom to early summer
Brown leaf edges, no distinct spots	Drought, heat or root stress	Summer

Orange: pear trellis rust

WSU Hortsense describes bright yellow to orange spots, up to about 1 inch across, on pear leaves, fruit, twigs and branches in spring and summer. The UConn Home and Garden Education Center adds that the spots can turn bright reddish orange in summer, and that tiny black dots appear in their centers by midsummer. Opposite the spots, on the underside of the leaf, acorn-shaped fruiting structures up to about a quarter inch high develop, most often in late summer.

The key to this disease is that it needs two hosts. WSU notes that spores from junipers infect only pears and spores from pears infect only junipers. On junipers, the fungus forms spindle-shaped galls that release orange, jelly-like spore masses in wet spring weather. UConn lists both ornamental (Callery) and orchard (common) pears as susceptible.

What to do:

Remove infected pear leaves, fruit and twigs by mid-August where practical (UConn).
Prune galls from nearby junipers before April 1.
Keep pears and susceptible junipers as far apart as you can. UConn cites recommendations of 100 to 1,000 feet.
When planting junipers near pears, choose resistant species such as Juniperus squamata, J. communis or J. horizontalis (UConn).

For a full treatment plan, including when sprays help, see our guide to rust on pear trees.

Red: pearleaf blister mite

WSU Hortsense describes pearleaf blister mites as tiny eriophyid mites that feed inside the leaf. Their feeding forms pale green to reddish blistered areas, usually ⅛ to ¼ inch across. Later in summer, the blisters turn brown to black as the tissue dies, and heavy infestations can make leaves drop. Fruit may show russeted, slightly sunken patches.

Blisters are raised and often clustered along the main vein. Rust spots are flat on top and bright orange. Predatory mites help keep blister mites in check, so avoid broad-spectrum insecticides.

Purple-black: Fabraea leaf spot

Penn State Extension describes the first signs as small purple dots on the leaves nearest the ground. They grow into circular, purplish-black or brown spots about a quarter inch across, each with a small black pimple in the center. In wet weather a creamy, glistening mass of spores oozes from the center. Leaves can carry dozens of spots and drop early. Fruit lesions are black and slightly sunken and can make the fruit crack.

UMass Amherst notes that the fungus overwinters in fallen leaves and spreads in rain from late spring through summer. Rake up and dispose of fallen leaves in autumn. In wet years, protective fungicides through spring and summer may be needed. Penn State recommends sprays in June and July, with extra applications in wet seasons on late varieties such as Bosc.

Black: fire blight

Fire blight is not a spot disease, but it is the most serious cause of blackened pear leaves. The Morton Arboretum describes blossoms that turn brown and then black about two weeks after opening, and new leaves that wilt suddenly. Infected shoot tips often bend into a shepherd’s crook. Remove infected branches at least 6 inches below the visible damage, on a dry day, and sterilize tools between cuts. See fire blight on pear trees and our guide to pear leaves turning black.

Brown with no spots

If leaves brown from the edges without distinct spots, the cause is more likely water stress, heat or root damage than a disease. See why pear tree leaves turn brown.

When to worry

Rust, blister mite and a light case of Fabraea are mostly cosmetic on an established tree, although heavy infections year after year reduce vigor and crops. Fire blight is the one to act on quickly. If you are not sure which you have, the Tree Symptom Checker can help you narrow it down by season and symptom.

Sources

Pear: Pear Trellis Rust, Washington State University Hortsense
Pear Trellis Rust, UConn Home and Garden Education Center
Pear: Pearleaf Blister Mite, Washington State University Hortsense
Leaf and Fruit Spot of Pear in Home Gardens, Penn State Extension
Fabraea Leaf Spot, UMass Amherst Center for Agriculture, Food, and the Environment
Fire Blight, The Morton Arboretum

Top photo: Antonios Tsolis, CC BY-SA 4.0, via Wikimedia Commons

Pear Leaf Spots by Color: Orange, Red, Black and Brown