COMANDRA BLISTER RUST
Fruit gall showing orange colored spores on loblolly pine.
Alternate host—false toadflax.
Comandra blister rust, caused by the fungus Cronartium comandrae, is a canker disease of hard pines. The disease presently occurs in widely scattered areas throughout the western, central, and southern United States. In the South, the primary hosts are loblolly, shortleaf, pond, and Virginia pine. Herbaceous plants of the genus Comandra, commonly known as false toadflax or comandra, are also attacked.
The fungus infects pines through the needles and grows from the needle into the branch or main stem where it forms a gall or canker. Dark orange-colored spores which are produced on the surface of the gall in the spring are wind-blown and infect the leaves or stems of the comandra plants. Two to three weeks after infection, urediospores are produced on the underside of the comandra leaf. These are wind-blown and can only infect other comandra plants. Eventually hair-like structures known as telia are produced on the comandra leaves and stems. The telia produce spores which are wind-blown and infect the pine host through the needle. The necessary combination of a susceptible pine host, the alternate host, and the pathogen is presently known to occur only in northern Arkansas, eastern Tennessee, and northern Alabama.
No effective method of controlling the disease in forest stands is presently known. Silvicultural or forest management practices which reduce the abundance of the alternate host offer promise of long term control. Maintenance of dense stands and heavy ground cover as a means of shading out the intermediate host plants, may be helpful in reducing rust damage in many areas.