WSU Whatcom County Extension

Integrated Pest Management for Raspberries

Yellow Rust

(Phragmidium rubi-idaei)

Insects and Invertebrates

 

Yellow Rust

 

Symptoms

Leaf infections in spring and early summer appear as yellow pustules on the upper leaf surface. Severely affected leaves may dry and die out. By summer, yellow spores begin to develop on the lower leaf surface. Fruit can die before maturing if attached to fruiting laterals containing several affected leaves. By the end of harvest, black spores can be found within the yellow spores on lower leaf surfaces.

 

Life History

Leaf infections in spring and early summer create a yellowish spotting on the upper leaf surface. At first the spots are very small, yellow to orange and slightly raised (spermagonia) but then new, yellow to orange spore bearing structures (aecia) are produced in a ring around these spots. By summer, another yellow spore stage (uredinia) appears on the lower leaf surface. These structures later darken as black teliospores.  Overwintering teliospores remain on the bark of floricanes and are the source of inoculum for the following spring, affecting emerging leaves and primocanes.

 

Monitoring

Scout 3-5 sites per field, (depending on field size) and evaluate 10-20 hills, spaced 3-5 hills apart on both sides of the aisle way. Starting in April, examine the oldest leaves on developing laterals near the wire for infection. Watch closely to determine when these pustules begin to sporulate. Record disease severity on a scale of 0-3. Continue to scout for symptoms associated with yellow rust through the beginning of June.

 

Thresholds and Management

No threshold or tolerance level available.

Delayed dormant lime sulfur applications can be made to reduce the viability of teliospores. Fungicides can also be applied early in the season to protect new foliage when sporulation begins.

Promote air circulation and proper drying of plant tissue through pruning and trellising to open plant canopy and allow leaves, flowers, and fruit to dry more quickly, subsequently reducing plant susceptibility. Cultivate in late fall or early spring to cover fallen leaves, old cane stubs, and debris before new leaves appear, thus eliminating inoculum sources. Remove and burn old fruiting canes soon after harvest and cultivate as soon as weather permits. Delay trellising until leaves have dropped from primocanes or strip leaves before tying.

 

Resources

Cornell University, Department of Horticulture: Berry Diagnostic Tool
http://www.fruit.cornell.edu/berrytool/raspberry/leavesstems/Rasporange.htm

Oregon State University Extension, An Online Guide to Plant Disease Control: Raspberry – Yellow Rust
http://plant-disease.ippc.orst.edu/ShowDisease.aspx?RecordID=959

University of California, IPM Online: Caneberries, Yellow Rust
http://www.ipm.ucdavis.edu/PMG/r71101111.html

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WSU Whatcom County Extension 1000 N. Forest St., Suite 201, Bellingham, WA 98225 (360) 778-5800 whatcom@wsu.edu