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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #108545
Title: FIRST REPORT OF PUCCINIA CANALICULATA ON SUNFLOWER

Author
item Gulya Jr, Thomas
item STEGMEIER, W - KANSAS STATE UNIVERSITY

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2002
Publication Date: 5/1/2002
Citation: Gulya Jr, T.J., Stegmeier, W.D. 2002. First report of Puccinia canaliculata on sunflower. Plant Disease. 86:559.

Interpretive Summary: Sunflower is the host for not one, but five different fungi causing "rust." One of these rust fungi is Puccinia helianthi, which is currently being considered as a "bioherbicide" to control a noxious weed called nutsedge. If this rust fungus is ever marketed commercially, sunflower growers should be aware that neighbors using this bioherbicide may unintentionally cause the disease to appear on cultivated sunflower. This rust is very rarely seen in the Midwest, but seed company and university personnel should be aware of it. It is also very similar in appearance to another rust found on sunflower, called cocklebur rust. The differences between the two rust fungi on sunflower are described to help avoid confusion.

Technical Abstract: Puccinia canaliculata (Schw.) Lagerh. is a macrocyclic, heteroecious rust found on Cyperus spp.(sedges) in N.&S. America, with aecial stage reported on Asteraciae. In July 1997, aecial pustules of unknown etiology were observed on over 90% of cultivated sunflower (H.annuus L.) plants in a field near Catherine, KS. Pustules were found on lower leaves of plants in the 6-10 leaf stage. Individual leaves had one to several pustules, usually convex, measuring 5-10mm in diam. In contrast, the aecial pustules of P.helianthi measure 1-2mm in diam. Aecial cups, yellow-orange color, occurred on leaf undersurface, with globoid aeciospores averaging 15 x 18.5u. Wild sunflowers (H.annuus) & cocklebur (X.strumarium L.), in the same & 2 nearby fields, had similar pustules. There was severe infestation of yellow nutsedge (Cyperus esculentus L.) in the sunflower field, but uredia were not found on the nutsedge because the plants had been killed with glyphosate. Based on the size of aecia, aeciospores & peridial cells from all 3 hosts, the fungus was identified as P.canaliculata. Although sunflower has been shown to be an alternate host, this is the 1st report of natural infection, & is significant in that it occurred in a major sunflower production. Since P.canaliculata is being considered as a bioherbicide for nutsedge control, non-target hosts, such as sunflower, need consideration. The possibility of laymen confusing P.xanthii & P. caniculata exists, since both occur on cocklebur & sunflower & produce pustules of similar size. However, since P.xanthii is a microcyclic autoecious rust while P.caniculata is a full cycle heteroecious rust, color difference between dark telia of P.xanthi & yellow-orange aecia of P.caniculata should easily differentiate the 2 species.