PINE-PINE GALL RUST Endocronartium harknessii   F A C T S H E E T

Introduction

Pine-pine gall rust is a disease that occurs on 2-and 3-needle pine trees. The disease is caused by the fungus Endocronartium harknessii. Other names for this disease include western gall rust and Woodgate gall rust. The name pine-pine gall rust indicates that the fungus spreads directly from one pine to another pine and does not require an "alternate" host as do other rust diseases on pines. As a result, this disease can quickly become severe on individual, infected trees and also spread readily in hedges and closely spaced plantings. In New York, Scots pine (Pinus sylvestris) is the most common host for pine-pine gall rust. Mugo pine (Pinus mugo) and Jack pine (Pinus banksiana) may also be infected. In New York, pine-pine gall rust is not usually a serious problem because most potential hosts are apparently resistant to the disease. However where highly susecptible strains are grown as Christmas trees, the disease may cause economic loss.

Symptoms

New infections occur on actively growing shoots and are practically undetectable for the first six months. About a year later swellings develop on infected branches. When numerous, these young galls impart a distorted, beaded appearance to the branch. Needles turn yellow then brown, and heavily infected branches may die. Many branches are not killed immediately and the galls enlarge, becoming spherical or round. Such galls may continue to enlarge for several years until they girdle and kill the branch.

Figure 1: A hip canker caused by a gall rust infection.

Figure 2: A typical gall on Scots pine.

Disease cycle

About three years after infection, spores of the fungus are produced on the surface of the galls. These spores are yellow, powdery, and burst out of blister-like structures. These yellow spore masses may begin to appear in New York from mid-April to early May and may produce infectious spores for about 6-8 weeks. At the same time, healthy young shoots are elongating and are susceptible to infection. Spores from the galls are wind-blown and some inevitably land on the young shoots. Infections follows during wet weather. The following year infected areas on branches begin to swell and form galls.

Management Strategies

Prune branches with galls and discard them before the galls have a chance to produce spores. Trees that are heavily galled or seedlings with stem galls should be removed and discarded in late winter or early spring before galls produce spores. It may be desirable for aesthetic reasons to prune dead branches killed by numerous infections. The fungus will not survive in dead branches. Wood from older trees may be safely used for firewood. Pesticide applications are not recommended for residential sites.

Created, KLS, 8/99; Updated SLJ 2/05