What’s The Buzz?
The days of summer are buzzing in the garden. But not all
that buzzes is bad. In fact, of the hundreds of species of insects found in
Wisconsin, fewer than 1% are serious threats to our ornamentals and crops. Many
of those insects that don’t cause problems are actually beneficial. Their main
roles are in pollination of flowers for fruit production and as agents of
biological control that keep many of the potentially pesky insects under
control. And then there’s the honey, the beeswax, the silk, etc.
Many “bugs” we see and hear buzzing around our gardens and
flowers are black and yellow striped like bumble bees by design. Only a few are
actually bees; many are really wasps and flies that mimic bees with this
coloration. Most of them are pollinators and predators of other species of
plant pests. A few may sting but usually not unless they are provoked
– or when
you scare them by flailing your arms, batting at them and screaming.
Granted, yellowjackets and bald-faced wasps sometimes need
no provocation at all. But they only represent a very small percentage of what’s
buzzing in the air, unless of course there’s open soda and food and its late
July or August.
All those others are buzzing beneficials, worshipping each
blossom and seeking out pests to destroy. They should be encouraged and
conserved through wise plant selection and intelligent pest management aimed at
the pests
– not these welcome guests.
Some
of the most common non-stinging bee mimics are probably hover flies (or flower
flies, in the family Syrphidae). They are common and important natural enemies
of aphids and other small, slow-moving insects. The adults are often seen
visiting flowers, hovering over the flowers and darting around. There are many
different species that range in size from less than 1/4 inch long to more than
3/4 inch long. Many have the typical black and yellow stripes on the abdomen
that give them a bee-like appearance, but others are hairy with a long, thin
abdomen. The adults need flowers as nectar and pollen sources. They are
attracted to weedy borders or mixed garden plantings that are also infested with
aphids. Some flowers that are especially attractive to hover flies include wild
carrot or Queen Anne's lace, wild mustard, sweet alyssum, coriander, dill, and
other small-flowered herbs. Females lay their tiny white eggs singly on leaves
or shoots near or among aphid colonies. The larvae that hatch in two to three
days are small legless maggots that range in color from creamy-white to green or
brown. They look somewhat slug-like and are tapered towards the head. The larvae
feed on aphids or other insects and move around on the plants in search of prey.
Although hover fly larvae feed mainly on aphids, they will eat small
caterpillars, thrips and other small insects.
There
are also many types of wasps that frequently visit flowers. The vast
majority of wasp species are incapable of stinging. Many of these stingless
wasps appear to have an external stinger, which, however, is the egg-laying
structure (ovipositor). In the stinging bees and wasps this organ is no longer
used as an ovipositor, but has become modified for defense. These small wasps
are generally parasitic on other insects. The stingless wasps comprise the
single largest and most important group of natural enemies of insect pests. The
adult female deposits her eggs in or on the host insect, and the larvae that
hatch consume the host as they complete their development, eventually killing
the host in the process.
– Sharon Morrisey, Milwaukee Co. UW-Extension Consumer Horticulture Agent
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