Insects and Diseases of Trees in the South

by Anonymous

CYLINDROCLADIUM ROOT ROT

This nursery disease is caused by two fungi species. Cylindrocladium scoparium and C. floridanum: Cylindrocladium root rot has been found on two hardwoods (yellow-poplar and black walnut) and two conifers (white pine and Fraser fir) in forest tree nurseries in six southern states. These include Virginia, West Virginia, North Carolina, Tennessee, Alabama, and Mississippi.

Leaf symptoms on 1-0 black walnut nursery stock.

Root rot symptoms on hardwoods and conifers are quite different. The most characteristic root symptoms on yellow-poplar and black walnut are the blackened and longitudinally-cracked infected roots that are in sharp contrast with healthy white roots of these two species. Infected seedling leaves become yellow and later turn reddish-brown.

Root rot symptoms on conifers involve either rotting of the seed or seedling (pre-emergence damping off) before emergence from the soil or seedling root rot following emergence. These symptoms also involve a shrivelling and reddening of foliage, needle blight, and stem cankers. The most characteristic symptoms are the “patchy” irregularly scattered pattern of infection in conifer seedling beds and the loosening of the root epidermis on infected roots—making it very easy to pull off.

Root symptoms on 1-0 yellow-poplar nursery stock.

The most practical and effective control for root rot diseases of this type involves strict quarantine to either keep the disease out of the nursery or keep it confined to known infected areas by avoiding the transportation of root material, organic matter, and soil from infected to non-infected seed beds. Soil fumigation may control this disease if applied under favorable conditions.