Prolonged aphid feeding results in a reduced harvest. The aphids are
small -- roughly 2 millimeters long -- and green. They are active
from spring right up until harvest, so applications at two-week
intervals may be necessary to keep them under control -- This is not
a one-shot solution. In addition to malathion, horticultural oil and
insecticidal soap are labeled to control currant aphids in
When you talk about the canes "drying out" and looking dead, I
wonder if more than one insect is to blame. Two insects that damage
canes through the growing season are the currant borer and currant
Currant borer larvae damage canes by feeding and tunneling inside
the pith of individual stems. They overwinter as mature larvae in
the stems, pupating and hatching as adults in spring. Adults are
clear-winged moths that strongly resemble wasps. Adults lay eggs on
currant stems in June; the small larvae tunnel into currant stems
soon after they hatch.
Aphids on Spirea
Currant borer larvae are pale yellow and worm-like. Promptly remove
infested stems at ground level, and send them out with the trash or
burn them. Do not leave them on the ground in the currant patch --
the larvae are mature enough to complete their development in cut
stems and would re-infest the planting.
There is no chemical
control once the larvae hatch and bore into the canes. Red
currants are more susceptible to this insect than other varieties.
Currant stem girdlers damage canes in two ways: adult egg laying and
larval feeding. The adults are sawflies that make numerous punctures
in canes as they lay eggs in spring, causing the new shoots to wilt
by late spring. The damage continues through summer as the larvae
hatch and begin tunneling through the canes.
The best recommendation is to remove and destroy infested canes as
soon as you notice the damage. There is no chemical control once
adults have inserted eggs into the stems.
Dealing with Rabbit Damage