Plant Disease Management Handbook

See:

Azalea (Rhododendron spp.) - Leaf and Flower Gall

Cranberry (Vaccinium macrocarpon) - Red Leaf Spot

Image related to Cranberry (Vaccinium macrocarpon)-Rose Bloom

Abnormal branch caused by Exobasidium oxycocci.

Photo by Peter Bristow, WSU-Puyallup.

Spores of Exobasidium oxycocci give a whitish cast to the surface of the swollen leaves.

Photo by Peter Bristow, WSU-Puyallup.

See:

Cranberry (Vaccinium macrocarpon) - Red Leaf Spot

Cranberry (Vaccinium macrocarpon) - Rose Bloom

Image related to Cranberry (Vaccinium macrocarpon)-Red Shoot

Uprights infected by Exobasidium perenne.

Photo by Peter Bristow, WSU-Puyallup.

Note the individual infected uprights.

Photo by Peter Bristow, WSU-Puyallup.

A cluster of infected uprights.

Photo by Peter Bristow, WSU-Puyallup.

See:

Cranberry (Vaccinium macrocarpon) - Red Shoot

Cranberry (Vaccinium macrocarpon) - Rose Bloom

Image related to Cranberry (Vaccinium macrocarpon)-Red Leaf Spot

Note the swelling and reddening of the stem.

Photo by Peter Bristow, WSU-Puyallup.

Colonization of the infected leaf and stem tissues by the fungus Mycosphaerella nigromaculans, the cause of cranberry black spot.

Photo by Peter Bristow, WSU-Puyallup.

Glossy, red spots on the upper surface of infected leaves (top row). Spores of the fungus are produced on the lower surface of leaves (bottom row). The leaf on the left end of each row is healthy.

Photo by Peter Bristow, WSU-Puyallup.

Cause The fungus Pyrenobotrys compacta produces a conspicuous disease, but it appears to cause little damage. Spores in the fruiting bodies (pseudothecia) mature in early summer and infect new leaves in summer or early fall.

Image related to Cranberry (Vaccinium macrocarpon)-Pyrenobotrys Leaf Spot

Fruiting bodies on the lower surface of infected leaves in mid-March.

Photo by Peter Bristow, WSU-Puyallup.

Purplish spots on the upper leaf surface (top row) and groups of fungal fruiting bodies on the lower surface of infected leaves (bottom row). A healthy leaf is at the right end of each row.

Photo by Peter Bristow, WSU-Puyallup.

Cause Although three Phytophthora spp. have been found in Oregon and Washington beds, P. cinnamomi is the most pathogenic. These fungus-like microorganisms have spores that swim to healthy plants, enter them, and destroy roots and runners under flooded conditions. Most beds with root rot were wet picked; root rot in dry-picked beds occurs in areas with poor drainage.

Note the dying patches within this cranberry bed.

Photo by Jay W. Pscheidt, 1991.

Image related to Cranberry (Vaccinium macrocarpon)-Phytophthora Root and Runner Rot

Damage caused by Phytophthora root and runner rot.

Photo by Peter Bristow, WSU-Puyallup.

Cause Three genera, the ring nematode, (Mesocriconema spp.), the stubby root nematode (Paratrichodorus spp.), and the sheath nematode (Hemicycliophora spp.) are the most common in the Pacific Northwest. A survey in the mid-1990s of 53 Oregon and Washington cranberry beds showed the incidence and population densities of these nematodes were slightly higher in weak areas of beds but not significantly greater than in strong areas.

Cause Several fungi including Godronia cassandrae (asexual: Fusicoccum putrefaciens), end rot; Phomopsis vaccinii, viscid rot; Botrytis sp., yellow rot; Allantophomopsis cytisporea and A.

Symptoms on fruit infected by different fungi are very similar, making it nearly impossible to distinguish between rots based on symptoms alone.

Frank Caruso.

Early Rot caused by Phyllosticta vaccinii.

Frank Caruso.

Ripe Rot caused by Coleophoma empetri.

Frank Caruso.

Fruit rot is characterized by any change in normal color or consistency of the berry during development such as softening, discoloring, or shriveling.

Frank Caruso.

Slide is labeled "cranberry fruit spot found in Bandon".

OSU Extension Plant Pathology Collection, 1963.

Cause A phytoplasma that is transmitted only by the blunt-nosed leafhopper. This disease was first detected in Wisconsin in the 1920's and subsequently brought into New Jersey and Massachusetts. The disease was noted in the 2001 edition of "Cranberry Production PNW 274" with symptoms observed in both Oregon and Washington. The disease is not spreading actively and is of only minor importance because the insect vector is not found in Western North America.

Cause A fungus, Protoventuria barriae, common in the cranberry production areas of Oregon and Washington. Whether it affects plant vigor or yield is unknown. It overwinters in the previous season's leaves and in dead leaves in the duff layer.

Image related to Cranberry (Vaccinium macrocarpon)-Early Leaf Spot

Notice the dull, reddish-purple spots on the upper surface of infected leaves (top row). Symptoms seen also on the lower surface of infected leaves (bottom row).

Photo by Peter Bristow, WSU-Puyallup.