HomeStrawberriesStrawberries: Leaves have spots

Strawberries: Leaves have spots

Leaf spots are the common symptom for several strawberry diseases such as:

Leaf spot

The fungus Mycosphaerella fragariae causes an infection which starts off as small purple spots on leaves. Later, spots have a narrow whitish to grayish margin. Sometimes lesions centers drop out, giving leaves a “shot-hole” appearance.

Strawberry leaf with irregularly distributed spots. Spots have brown border and white center that occasionally falls out to make holes.

Strawberry leaf with reddish discoloration in v-shape starting from outer margins. Brown-bordered spots with white center scattered across leaves.

Fruit infections may also occur with this fungus. They are called “black seed” as the infections center around individual seeds (achenes).

Ripe strawberry fruit with small, sunken, black tissue surrounding 1-3 seeds.

Stem lesions may also be evident on leaf petioles and runners.

Strawberry stem with black cankerous lesion spreading to immature rootlets. Leaves sprouting from stem have necrotic tissue in v-shape pattern starting at tips.

More information about leaf spot.

Leaf blight,

Leaf blight is caused by the fungus Phomopsis obscurans. Symptoms start off as small, brown spots surrounded by a wide purple halo.

Strawberry leaf marked by spots with purple border and brown center. Spots are present between veins, and some lesions appear to be traveling along veins. Veins with lesions are slightly wider than surrounding veins, and have a purple tinge.

Lesions forming from the leaf margin inward are often v-shaped in appearance.

Strawberry leaves covered in purple spots with brown center. V-shaped purple discoloration spreading from leaf tips towards leaf center.

More information about leaf blight.

Leaf scorch

The fungus (Diplocarpon earlianum) causes a disease which off as small purplish leaf spots.

Strawberry leaves marked with deep purple spots. Spots are uniformly purple in color but variable in shape in size. Some appear spherical while others are rectangular. Some spots are merged to create uniformly purple sections on leaf.

Spots quickly fuse into large reddish purple patches on leaves, giving leaves a characteristic burned look.

Strawberry leaves marked with purple spots and large red patches. Red patches have purple spots. Patches do not form any distinctive pattern on leaves.

More information about leaf scorch.

Angular leaf spot

The bacterium Xanthomonas fragariae causes an infection that starts off as small, angular, dark green ,”water-soaked” spots on the undersides of leaves.

Strawberry leaf underside with muddy appearance, caused by many brownish, wet-looking spots. Spots are scattered across leaf like a mud splatter. One leaflet is almost entirely brown, one leaflet has a large brown area on one half and only a few speckles on the other half. The third leaflet is evenly scattered with many disparate speckles.

Strawberry leaf with brown speckling across its surface. Speckles are small, but merge along veins to form long lines of discoloration. The discoloration is not present on top of leaf veins.

The angular spots between the veins are visible with top lighting …

Top lighting on strawberry leaf mottled with red and dark green spots. Spots have sharp edges and are distinctly non-spherical.
Top lighting on strawberry leaf infected with angular leaf spot (Xanthomonas fragariae).

…and back lighting.

Back lighting on strawberry leaf mottled with red and translucent green spots. Spots are distinctly angular in shape, with sharp edges and square or trapezoid shapes.
Back lighting on strawberry leaf affected by angular leaf spot (Xanthomonas fragariae). Note the translucent “windowpane” effect.

Eventually these coalesce, and the leaf appears scorched.

Close-up of strawberry leaves that appear shriveled and discolored. Many brown-colored spots are scattered across the leaf, often bordered by yellow tissue. Many spots spots have merged to form large necrotic areas along the leaf margins. The tissues closest to major leaf veins, particularly at the base of the leaf, are still green.
Photo courtesy of Kathleen Demchak, Penn State University.

Note: There are several methods to differentiate angular leaf spot from leaf scorch.

The presence of angular lesions between veins on the lower sides of leaves is indicative of angular leaf spot. These symptoms are not caused by leaf scorch.

Strawberry leaf with large necrotic center surrounded by yellow tissue marked with red spots.

Strawberry leaves with red spots visible on outer edges of leaf surface. Individual spots are about the size of a pin-head, but some have merged to form a reddish patch on a leaf tip.

Sometimes strawberries can be attacked simultaneously by leaf scorch fungus and angular leaf spot bacteria. It is hard to distinguish between scorch  and angular leaf spot  when viewing leaves from above. Holding leaves up to the light contrasts the “windowpane” effect of angular leaf spot to the dark spotting caused by scorch.

Brown and red spotting on two lobes of strawberry leaf. The right lobe has yellow and red discoloration and is slightly more colorful than the left lobe, which has only purple-brown discoloration. The spots on the left lobe are slightly more spherical in shape than those on the right.
Leaf scorch (Diplocarpon earlianum) on left, and angular leaf spot (Xanthomonas fragariae) on right. Photo courtesy of Kathleen Demchak, Penn State University.

 

Underside of strawberry leaf held up to the sun. Sunlight shines through the right lobe, creating "windowpanes" with yellowish and red color. The lesions on the right half of the leaf do not transmit any light and appear deep reddish-purple..
Leaf scorch (Diplocarpon earlianum) on left, and angular leaf spot (Xanthomonas fragariae) on right. Photo courtesy of Kathleen Demchak, Penn State University.

Sepals or “caps” may also be infected by angular leaf spot.

Green strawberry fruit with uniformly grayish-brown cap.
Photo courtesy of Kathleen Demchak, Penn State University.

More information about angular leaf spot (scroll to the bottom of the page to view additional resources).

Use these resources if you need additional help with diagnosis and to find solutions to your problem.