removing Oregon Grape

Asked May 26, 2018, 8:01 PM EDT

I have an area 10X10 feet of Oregon Grape that has developed "rust" spots. The area is by the fence and no other plants are around it. I want to remove the entire area of all the plants. What is a safe way that is recommended? Thank you.

Washington County Oregon

1 Response

Oregon Grape (Mahonia aquifolium)-Rust diagnosis is included to make sure you have properly diagnosed your plants condition. Information on total plant removal is also included.

Image related to Oregon Grape Mahonia aquifolium-RustImage related to Oregon Grape Mahonia aquifolium-Rust

Note the yellow, reddish lesions causing the leaves to pucker. Numerous small spots are common on Oregon Grape.Jay W, Pscheidt, 2008 and Photo by Jay W. Pscheidt, 1994.

Cause Cumminsiella mirabilissima and Puccinia graminis, fungi. These diseases can be spread through infected nursery stock. Cumminsiella mirabilissima has all spore stages on the same host, while P. graminis has grass alternate hosts such as wheat. The movement of rust resistant cultivars is not regulated.

Telia of C. mirabilissima occur on leaves in the fall and teliospores are abundant in March and April. Newly emerging leaves are infected by basidospores produced from teliospores. Pycnia then develop on the upper leaf surface from late April to mid-June. Aecia then develop on the undersides of leaves along veins, petioles and leaf margins or even on fruit, especially by the end of May. By late June uredinia can be found on the undersides of leaves. By fall telia are produced in the center of the uredinia.

Symptoms Reddish spots on older leaves which develop dark centers (telia). Severe infections cause leaves to be puckered and distorted and may lead to premature defoliation. The aecidial stage, on younger leaves, is rare. On older leaves, once aeciospores are released, infected areas abscise and develop a shot-hole like symptom. The golden yellow margin of the peridia distinguishes C. mirabilissima from Puccinia graminis, which has a whitish or yellow margin.

Cultural control for the infection:

· Avoid overhead irrigation.

· Remove and destroy infected leaves.

· Grow rust resistant cultivars or species.

Chemical control: (Protect newly emerging leaves)

· Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. H

· Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H

Reference: https://pnwhandbooks.org/plantdisease/host-disease/oregon-grape-mahonia-aquifolium-rust

Total plant removal and solarizing soil:

Pull or cut plants as close to the surface as possible. Remove all the plants from the infected area, including plants leaves and other debris. Dispose of plants and debris by burning or dispose in garbage bags. Because the plants might contain fungal spores, dispose of them rather than transplanting them elsewhere in your garden. Sterilize garden tools with steam or isopropyl alcohol.

  • To properly treat the soil, you must heat the soil to a temperature that can also kill the plants.

· Water the soil until it's saturated. When you pick it up and squeeze it in your hand, it should be too wet to maintain a ball shape. The moisture helps create a steamy environment that kills most fungal infections.

· Place two layers of clear greenhouse plastic or thick plastic sheeting over the bed. Secure the edges by driving landscape staples through the plastic and into the ground with a rubber mallet. Place the staples every 6 inches along each side.

· Allow the plastic to solarize the soil for about six weeks. The plastic holds in the heat, increasing the temperature in the soil high enough to kill most fungi. This process works best in the hottest summer months.

Things You Will Need

§ Greenhouse plastic or Clear plastic sheets

§ Landscape staples

§ Rubber mallet