They are prevalent in
the South and are primarily cotton pests but also attack legumes, egg-
plant, and some other vegetables, citrus, pecan, and sunflower. Some stink
bugs act as vectors of plant disease, distributing the organisms causing
yeast spot of lima bean, kernel spot of pecan.
CANKERS AND DIEBACK
A canker is a localized lesion or diseased area, usually on a woody
structure. In its definitely limited character a canker is comparable to a
leaf spot on foliage, but a canker may continue to enlarge until it girdles
a cane, stem, or tree trunk, killing the water-conducting tissues and causing a dying back from the tip. Some diseases known under other names
have a canker as part of the symptom picture, like that formed on a limb
after a branch has died from fire blight. Some diseases commonly called
cankers, like boxwood canker, are more properly blights.
BROWN CANKER OF ROSE (Cryptosporella umbrind).
This is one of the
more important rose diseases. Very small purplish spots on the
canes acquire white centers and reddish-purple margins, there being numerous spots on a single cane. During the winter, especially on parts of
a cane kept moist with a mulch, the spots grow together into large
cankers, sometimes several inches long, with tan centers, purple or red
borders, and little yellow tendrils of spores protruding in wet weather.
If the cankers expand around the cane to girdle it, there is subsequent
Control. Cut out infected canes at spring pruning. Avoid leaves, manure, and other moist mulches over winter. If a copper spray is used
weekly for black spot control, brown canker will automatically be taken
care of. I almost never have a case of brown canker in gardens regularly treated with the ammoniacal copper in Tri-ogen.
COMMON, or STEM, CANKER OF ROSE (Leptosphaeria coniothyrium).
is an indefinite canker, smudgy from the dark fungus spores massed
under the cane epidermis. The fungus is a weak parasite and enters
through pruning or other wounds; it cannot penetrate unbroken healthy
tissue. A frequent means of entrance is through long stubs left in pruning
or in cutting roses through the season, for the rose stem usually dies back
to the node, that is, bud or leaf axil. Frost cracks provide another common
means of entry.
Control. Always cut a rose stem just above a leaf or bud; never leave
more than 1/4 inch of stub, less if possible. Avoid feeding and watering
late in the season; this encourages succulent tissue ready to split at the
first drop in temperature.