February 25, 2026
Tomato pin worms are usually only a problem in greenhouses in
northern latitudes but they can also be a serious pest in the south.
These are the larvae of small moths. Eggs are laid on the
tomato foliage where they hatch and burrow into the leaf, very similarly like
leaf miners. I have on numerous occasions split these “mined” leaves to find
very small caterpillars inside. The largest caterpillars found are 1/32nd of an
inch (about ¼ the height of the capital letters of this text). As they continue
growing some will burrow into the side of the fruit. A slight indentation
centered on a small dot is the only outward appearance that they are present in
the fruit. They then burrow into the
ground to pupate and start this all over again. Several generations can mature
each year. The egg to adult cycle is 28 days.
The first year I had them, they destroyed my late harvest of
tomatoes. To the untrained eye the plants looked like they were old and in a
state of decline. This is deceiving, older plants decline from older foliage
towards younger. Pinworms work in
reverse. Since they are killing the growing points the plants soon expire.
Fully intact row covers that extend to the ground are the
best defense. This can be a problem because these are a pest you see in late
summer when fabric can start to become a little bit ratty. It is best to replace the fabric as soon as
holes develop. This was a clue to me the first year I had these “guests” all
the covered plants looked wonderfully healthy, whereas the uncovered ones were
unhealthy looking.
If you do find you have these guys, a seven day spray cycle
is needed for 28 days to make sure all generations are controlled. Since these
are moths Bt. works very well on them. Because insects can build up immunity to
Bt., a rotation with cold pressed neem oil is suggested.
By all means once you do start the spray schedule; cover your
toms with new fabric to prevent any new infestation.
Once you do discover you have these pests it is hard to
eradicate them because they will infest any of our wild Solanaceae plants.
Questions? I can be
contacted at markdirtfarmer@gmail.com. Or more
garden notes at redwagonfarm.blogsot.com
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