These Borers have been
found in the stems of Strawberry leaves and the much larger main stems
of Hollyhock and various other Plants and weeds. The Larvae appear to be
identical and thrash their front ends around violently when disturbed.
Some Borers attack roots, some
attack stems, some bore through the bark of trees where they may girdle
the Cambium layer causing the tree to die. Often there is a pile of sawdust
or excrement below the access hole.
Normally, they cause very little
crop damage, but a large invasion may lower the harvest noticeably. Pesticides
are largely ineffective, since the Larvae are protected by their host plant.
Preventive sprays meant for the egg-laying adults will also effect insects
which are beneficial.
If you have a valued plant,
and discover the Borer at an early stage, you may be able to limit damage
by drilling a 1/8" hole about 2" above the hole made by the Larvae(away
from the roots).
Then forcefully inject insecticide
into this new hole with a squirt bottle or injection needle. The one shown
is from a printer refill kit. Whatever you use will become contaminated
by the insecticide and should be reserved for this purpose or disposed
leaves on this main stem have wilted from lack of moisture and nutrients
because a Borer is living in the stem and preventing the upward flow. They
are usually found between the hole and the tip, rather than on the root
side of the hole.
Note the access hole indicated
by the blue line; it may have been made by the ovipositor of the adult
female insect, or by the Larvae which hatched and bored into the stem,
or by the resident Larvae to get oxygen or remove its excrement. The leaves
below the hole have access to nutrients and appear to be normal and healthy.
photo shows the stem sliced in half exposing the larvae.
same Larvae eating the stem and also showing its excrement left behind
stem with 9 leaves shows the destruction of borers called "Miners"
inside the leaves.
the actual Miner can be seen inside the black circle, appearing as a black
Tomato has what appears to be the damage of a Miner. Borers have also been
found inside Tomatoes!