Bindweed Rust, Puccinia convolvuli. View of the fungus on the upper surface of Hedge Bindweed leaves (Calystegia sepium).

Bindweed Rust, Puccinia convolvuli. View of the fungus on the underside of Hedge Bindweed leaves (Calystegia sepium).

A week ago (11th September 2018) Vanna and I took the train to Woodbridge in Suffolk. It’s a lovely place to visit, with interesting old buildings, good pubs and independent shops and walks beside the River Deben. We visited the churchyard of St. Mary’s Church, to see a large and impressive nesting aggregation of Ivy Bees (Colletes hederae). There were masses of male bees flying low over the ground, looking for females emerging from nest holes. Each female was surrounded by a cluster of male bees, forming a mating ball, in which one lucky male was able to mate. A few females had already mated and were digging out their nest holes or flying off to nearby Ivy to collect pollen and nectar. We chatted with several visitors, who had seen us taking photographs and read printed signs thoughtfully put there to explain what the bees were doing.

After a pub lunch we walked down a footpath next to an Ivy covered hedge, on the hunt for more bees to photograph, but we were soon distracted. Near the start of the path there was a big patch of Hedge Bindweed, Calystegia sepium, and Vanna noticed that many of the leaves were covered in orange-brown pimples. On closer inspection these appeared to be some sort of rust, which we didn’t think we’d seen before.

When we came home I did an online search and found out from the excellent Plant Parasites of Europe website that the fungus was probably Puccinia convolvuli. Vanna also posted photos on Facebook, on the British Plant Galls site, and Malcolm Storey confirmed the identity of the fungus. Previous records in the UK have been of only a few pustules per leaf, rather than whole leaves covered in them.

Puccinia convolvuli has only recently been discovered in Britain and there have only been a handful of records so far, the first from near Weymouth in Dorset in 2009. I sent the details of our find to the Suffolk Fungi Recorder, Neil Mahler, and he confirmed that our sighting was the first record for Suffolk. Since we came home we’ve been looking at Hedge Bindweed here in Norwich, but haven’t seen any infected plants here yet.

Further afield, Puccinia convolvuli occurs in other parts of Europe and in Asia and North America. It will also infect other species of bindweed, including Mallow Bindweed (Convolvulus althaeoides), Field Bindweed (Convolvulus arvensis) and California Rose (Convolvulus japonicus, now known as Calystegia japonica).

Although Hedge Bindweed (Calystegia sepium) has lovely flowers, it is often a troublesome weed, as it grows very vigorously and has deep roots that are hard to dig out. As Puccinia convolvuli can cause extensive damage to the plant, it is not surprising it has been studied as a possible biological control of Hedge Bindweed. In his 1992 Masters thesis Jonathan Beener of Eastern Illinois University concluded that further investigation was worthwhile. (Beener, Jonathan C., “Evaluation of Puccinia convolvuli (Pers.) Cast. as a Biological Control of Calystegia sepium (L.) R. Br.” (1992). Masters Theses. 2118.). There have also been several studies biological control of bindweeds by another fungus, Phomopsis convolvulus, such as in the journal Weed Science (Morin, L., Watson, A., & Reeleder, R. (1989). Efficacy of Phomopsis convolvulus for Control of Field Bindweed (Convolvulus arvensis). Weed Science, 37(6), 830-835.)

Both Jonathan Beener’s thesis and the Phrygana website state that Puccinia convolvuli prefers growing in more humid places. This means that  growth of the fungus is restricted in more open situations (such as fields), which could limit its use as a biological control. It will be interesting to see how the fungus spreads throughout the British Isles, and whether it does better in wetter western areas.

Worldwide, Puccinia convolvuli is not the only rust that grows on bindweed. In 2003 a related species of Puccinia was identified in Japan, Puccinia calystegiae-soldanellae, growing on Sea Bindweed, Calystegia soldanella (Zhuang Li, Teruo Sano, Takashi Fujita, Fusaka Nakai, Yukio Harada (2004). Puccinia calystegiae-soldanellae, a new rust species on Calystegia soldanella from Japan. Mycoscience, 45 (3),Volume 45, Issue 3, pp200 – 205.)

When you go for a walk, keep an eye open for infected bindweed leaves and, if you find any infected with Puccinia, send a record (with photos) to your local fungi recorder. To help you, you can compare specimens with the excellent photographs of Puccinia convolvuli on the Plant Parasites of Europe website, Bioimages and Phrygana websites.

The photos on this page are by Vanna Bartlett.