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Syrphid flies. Pollinators and
biological controls. Their larvae feed on aphids
© Beatriz
Moisset
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More gardeners are learning about
pollinators and creating habitat for them. It warms my heart when I
see them selecting plants beneficial to pollinators, converting
portions of the lawn into flower plots, cutting down on pesticides,
and creating the right conditions for pollinators’ nests. Many
gardeners are learning to be grateful to pollinators for their
services. Some are familiarizing themselves with the most common
ones. This is a healthy trend.
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Syrphid fly larva devouring aphids
©
Beatriz Moisset
|
An additional advantage of
pollinator gardens is that they serve another useful function. Many
other beneficial insects depend on pollinator gardens and, in turn,
gardens and farms profit from their presence. I am referring to
predators and parasites of plant-eating insects. Such beneficial
insects have earned the name of biological controls, or biocontrols
for short. Many biocontrols need nectar, or nectar and pollen, during
part of their life cycle. Some of them prefer to eat insects but can
survive on nectar and pollen in the absence of their prey. Thus they
are ready to spring to action when the unwanted pest arrives. Gardens
lacking on floral resources are not as well protected against pests.
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Tachinid fly, Trichopoda
pennipes. Its larvae feed on insects
© Beatriz Moisset
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The extra bonus of growing a
pollinator garden became apparent in studies done by Cornell University. Apple growers could cut down pesticide treatments from
ten to two or three a year when they started growing plants for
pollinators.
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Robber fly, Laphria thoracica,
a formidable hunter of insects
© Beatriz Moisset
|
It is a great thing that the needs
of pollinators and those of many biocontrols overlap. Syrphid flies
illustrate this point. The adults are bee-like and hover over
flowers, earning them their common names, flower flies or hover
flies. They feed on nectar and pollen and manage to do some
pollination. Their larvae are little green maggots that feed
voraciously on aphids. They frequently escape notice. I have learned
to check aphid colonies and frequently I find some of these maggots
doing what they do best, getting rid of aphids.
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An ichneumonid parasitic wasp
Its impressive appendix is an
ovipositor (egg laying organ), not a stinger
So there is nothing to fear from this
wasp
© Beatriz Moisset
|
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One of the solitary predatory wasps,
potter wasp (Eumeninae)
hunting a caterpillar hiding on the
flower head
© Beatriz Moisset
|
Here are a few other examples of
biocontrols that prosper in pollinator gardens: Tachinid flies, some
of which are hairy, robust and rather ugly, while others are elegant
and colorful. All lay their eggs on or in other insects and help
control many pests, even gypsy moths and Japanese beetles. Robber
flies are fast fliers and skillful at pouncing on unsuspecting
victims. Wasps are great garden helpers, both the parasitic ones,
which lay eggs on other insects, and the predatory ones, which catch
prey to feed their babies. The adults feed primarily on nectar and
pollen. It is good to remember that parasitic wasps don’t sting and
that most predatory ones are not inclined to do so. In most cases
there is no need to fear these wonderful biocontrols. Assassin bugs
have front legs that resemble those of praying mantises and, like
them, use them to grasp their prey with a swift movement. Not all
stink bugs are plant pests; the predatory ones feed on the pests
themselves. The merits of lady beetles as eaters of aphids and other
soft bodied insects hardly need mentioning. Both larvae and adults
feed on these pests. The adults are also fond of nectar and pollen.
Other beetles worth mentioning are the soldier beetles, so called
because their colors and pattern resemble those of old army uniforms.
They are frequently seen visiting goldenrods.
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Assassin bug, Zelus luridus
©
Beatriz Moisset
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Among the plants that feed both
pollinators and biocontrols are many Asteraceae, such as coneflowers,
coreopsis, yarrow, and goldenrods. Other families include Apiaceae,
the carrot family, Lamiaceae, the mint family, Euphorbiaceae, the
spurge family, and Fabaceae, the pea family. The best information on
planting for pollinators by region is provided by the Pollinator Partnership. You can also find some information in Attracting Beneficial Insects with Native Plants.
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Soldier beetles, Chauliognathus
©
Beatriz Moisset
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In summary, your pollinator garden
does double duty, helping pollinators and also biological controls.
Perhaps we could say that it does triple duty, as many of the flowers
are beautiful and we get to enjoy them too. Happy plantings!
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Polished lady beetle, Cycloneda
munda
© Beatriz Moisset
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References
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