No yawning over these bugs yet they do bore
Various insects are called borers, in
recognition of their method of entering their home. They chew their
way into a branch, twig, leaf stalk, root, etc. Some are weevils
(immature beetles), many are caterpillars and even a few maggots
(fly larvae) follow this lifestyle.
Most borers are attracted to weak plants,
perhaps by telltale smells or visual signals. The adults lay eggs
in opportune places, such as weak crotches or soft new tips, where
thin bark or splits in wood and weak cell walls will give way
easily to tiny chewing mouths of insects just emerged (eclosed) from eggs.
The symptoms: Plants attacked by borers most
often give us notice of the attack by general weakening, yellowing,
wilting -- especially during stressful hot periods -- and
undersized leaves and few flowers.
So the first line of defense against borers is
to keep a plant growing well, in a situation that promotes fast ,
strong growth and quick replacement of parts lost to borers.
If general plant health improvement doesn't curtail borer
damage, the next tactic is to try to kill the young as they
emerge. It's the old "aim at the weakest link" strategy.
Older borers are usually protected within the plant, unreachable to
our chemical killers or in resting/transformational stages when
poisons that must be ingested can't affect them. But the first
attack comes from exposed eggs, which can be killed with a
smothering oil applied at the right time, or an insecticide that
will coat the plant in those places borers will chew. This tactic
requires knowing what kind of borer, to know the life cycle --
especially when egg laying occurs.
We've covered numerous borers in our time on this beat but we'll
probably never cover them all. Too many plants and plant
groups, each with their own borer -- species that evolved
If you suspect borers are at work -- exit holes in bark being
one sign -- search a plant health management index or the Internet
using plant scientific name followed by the word borer. Select .edu
sites for Extension bulletins, .gov for foresetry and agriculture
department reports, etc.
Here are links to some borers we've covered, and back issue
numbers to look for.
- Dogwood borer (attacks many plants including hydrangea) What's
Coming Up 140
- Emerald ash borer (devastating to true ash, Fraxinus species,
in North America) What's Coming Up 36, What's Coming
Up 39 and
What's Coming Up 86
- Lilac/ash borer (may feed on certain other plants)
What's Coming Up 63,
What's Coming Up 114
- Pine borer, What's Coming Up 41
- Rhododendron borer, What's Coming Up 11
- Rose/Bramble cane borer,
What's Coming Up 40
- Viburnum borer, attacks trunk, What's Coming Up 92
- Viburnum tip borer, What's Coming
An issue number without a link means the issue was not yet up on
the site when we wrote this. Check the Ensemble Weekly Edition section
cover page where back issues are listed, for that issue's
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