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Disease Note. Russian Knapweed Rust Caused by Puccinia acroptili in New Mexico. M. E. Palm, USDA, APHIS, Systematic Botany & Mycology Laboratory, BARC-West, Beltsville, MD 20705. S. G. Vesper, USDA, APHIS, Albuquerque, NM 87102. Plant Dis. 75:1075. Accepted for publication 15 June 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-1075E. Russian knapweed (Centaurea repens L.) was introduced into North
America in 1898 from Eurasia (1,2), and this persistent, aggressive
weed is an increasing problem in much of the western half of the
continent. During a noxious weed survey in New Mexico in September
1990, four specimens of Russian knapweed heavily infected by a rust
were collected from a moderately dense stand in San Juan County.
The fungus was identified as Puccinia acroptili P. Syd. & Syd. based
on the uniformly echinulate urediniospores with conspicuous caps on
the three equatorial germ pores and closely punctate-verrucose teliospores
with a hyaline, usually persistent pedicel (2). This apparently
host-specific fungus, which has been reported (1) to inflict considerable
stress on heavily infected plants, may have potential as a biological
control agent. P. acroptili has been reported in North America from
British Columbia, Saskatchewan, California, and southern Arizona,
but this is the first report from New Mexico and suggests natural
eastward spread of the fungus along with its host. A voucher specimen
has been placed in the U.S. National Fungus Collections (BPI),
Beltsville, Maryland. |