Powdery mildew and rust of gooseberryleaf globemallow

Co infection/Dual infection of Sphaeralcea grossulariifolia with Rust [Puccinia sherardiana] and powdery mildew [Leveillula taurica].

R.K. Sampangi
Parma R & E Center, University of Idaho, Parma, ID 83660
Email: Sampangi@uidaho.edu
S.K. Mohan and C.C. Shock
Malheur Experiment Station, Oregon State University, Ontario, OR 97914

Host: Sphaeralcea grossulariifolia (Hook. & Arn.) Rydb.
Disease name: Powdery mildew and rust of gooseberryleaf globemallow
Pathogen name: 1) Leveillula taurica (Lev.) G. Arnaud (=Oidiopsis taurica E. S. Salmon)
                            2) Rust: Puccinia sherardiana Körn

Leaves of globemallow (Sphaeralcea grossulariifolia : Family Malvaceae) were found infected with both powdery mildew (Leveillula taurica) and rust (Puccinia sherardiana ). Powdery mildew was observed in early June-July followed by rust in August. Symptoms consisted of extensive growth of white, superficial powdery coating initially on the abaxial surfaces, which later spread to both leaf surfaces with abundant chasmothecia, mostly on older leaves. Rust infection started in the low to midcanopy and quickly moved up the plant. Rust appeared as small, orange-to-gray spots on the adaxial surfaces and along leaf margins, increasing in size over time, spreading onto the upper leaf surfaces, stems, and branches. Flowers were not affected. Rust pustules turned from gray to tan, reddish-brown, and ultimately the plants were killed. Taxonomically very diverse obligate pathogens, powdery mildew and rust, parasitized the same host tissue.