Agriculture Reference
In-Depth Information
using overhead irrigation. During dry weather in summer, prune to remove
all cankers, disinfecting your tools between cuts using 70 percent alcohol or
a solution of 9 parts water and 1 part household bleach. Delay your summer
pruning until after harvest, when the weather is dry.
Completely remove limbs below cankers. Some fruit specialists recom-
mend cutting away cankered areas to leave healthy tissue, but doing so may
increase the risk of future infections. Completely remove and destroy badly
infected trees, and do not allow the roots to regrow.
Copper bactericides are not always effective against bacterial canker, and
resistance to copper has been observed. Continue your routine Bordeaux and
copper treatments, but do not count on them to provide complete control
of bacterial canker. Do not apply Bordeaux mix or other sulfur products to
apricots. The best control is to use resistant varieties.
Bacterial Spot
A widespread and serious disease of stone fruits in eastern North America,
bacterial spot affects apricot, nectarine, peach, and plum. The disease is
primarily a concern in areas that receive more than 20 inches of precipita-
tion per year. The bacterium
Xanthomonas pruni
attacks the twigs, leaves,
and fruits of susceptible varieties.
Symptoms.
Spring infections first appear as dark flecks on peach skins or
water-soaked spots on smooth-skinned stone fruits. These spots gradually
become sunken and can form very deep lesions on the fruit. Summer in-
fections start as yellowish spots on the fruit. Angular lesions form between
the veins on leaves and create a tattered appearance as the centers of the
lesions fall out. Infected leaves turn yellow and drop early. On the wood,
cankers develop near twig tips during spring, damaging or killing the tips.
Summer infections appear as dark, irregular, sunken lesions on current-sea-
son shoots.
