Alan
McNab
Professor of Plant Pathology |
|
| BEET
DISEASES |
|
|
Cercospora
Leaf Spot, caused by the fungus Cercospora beticola, is charachterized
by spots that are brown to gray with distinct reddish-purple borders.
The fungus overwinters in residue from diseased plants or on seed
and is spread by splashing water, insects, tools and implements used
for cultivation, workers, and wind. High humidity and moderate temperatures
promote disease development |
| |
Phoma Heart-Rot,
caused by the fungus Phoma betae is characterized by seedling damping-off,
leaf spots, and root rots. Leaf spots are light brown, have poorly
defined margins, and can enlarge to about 1 inch in diameter. Root
rots begin as watersoaked areas that turn brown and finally black.
Rots are dry and firm unless invaded by a soft-rot bacteria. The causal
fungus overwinters on seed and in residue from diseased plants, and
is spread by splashing or running water. Plants weakened by adverse
growing conditions are most likely to be affected. |
|
|
Root Rot Complex
is caused primarily by Pythium ultimum with Rhizoctonia solani
as a secondary invader or as a primary invader in older beets. Symptoms
include preemergence and postemergence damping-off, root rot, stem
rot, and external and/or internal dry rot of fleshy roots. Pithium
and Rhizoctonia fungi are natural inhabitants of soil. Root rot is
most prevalent in cool wet soil, in fields planted yearly to beets,
and in plantings exhibiting poor vigor. |
|
|
Scab,
caused by Streptomyces scabies, the same fungus that causes potato
scab, is characterized by corky spots on the surface of beet roots.
Acidity levels above pH 5.2 promote fungus growth and disease development |
|
|
Boron Deficiency
causes black spots inside beet roots and large black dry rots
on the root surface. Dead cross-hatched areas may appear on the inner
concave surface of leaf stalks; young unfolding leaves may turn brown
or black and die. A heart-rot may develop in the root where leaves
were killed. Also, dead areas may develop at cambial rings within
fleshy tap roots. Boron deficiency is most prevalent in alkaline soils
high in calcium, and is promoted by dry conditions. |
|
){kind=link}
){kind=link}
){kind=link}
){kind=link}