Veronica rust observed on plants in Michigan

Members of the Mich. St. Univ. Extension report several cases of Veronica rust (Puccinia veronicae-longifoliae) showing up on perennial Veronica spp. in wholesale nursery growing operations and retail garden centers. The fungus can also attack annual Veronica species.

Hosts include Veronica longifolia,V. Montana and V. spicata. Symptoms include a bronze, purplish-overcast on the upper surface of infected foliage and raised, reddish-brown pustules on the underside of foliage. When the disease is severe, significant foliar blighting occurs.

Veronica rust was unintentionally introduced in Michigan in 2004 and was found again in 2005. The disease occurred on field-grown Veronica. To date, it has been a problem in very few nurseries.

Long- distance spread of the disease is thought to occur when infected propagation material is moved. Spores produced on foliage are carried by wind currents. Minimizing overhead watering  can reduce the spread of rust and other foliar pathogens that can infect Veronica.

Carefully inspect incoming plant material for signs of rust. Pay particular attention to material that originates from offshore. Plants with rust pustules or other disease symptoms should be destroyed. If only a small number of plants are infected, removing rust-infected leaves may help to reduce the spread.

Fungicide applications must be used preventively rather than curatively. Resistance development is a concern so rotate applications between chemical classes.