If we find a grub or two every time we dig, we are not alarmed
at all but glad.
- Grubs become beetles, and there are
thousands of species of
- There are probably hundreds of beetle
in every average,
healthy North American garden.
- The majority of beetles eat other insects
break down dead things
that would otherwise stack up
like trash during a
- It's tough to know one grub or pupa from
but we know this:
Chances are it's on its way to
becoming a beetle that
will work 24-7 without pay,
hunting harmful insects
and improving the soil.
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Below: Dung beetles, eeew, enough said. Except, what would
happen if dung eaters didn't exist and poop accumulated
Okay, grubs (below) are squishy, squirmy, and dingy
white. However, intestines are squishy and creepy, too. Would you
do away with your intestines on the basis of their looks?
Pesticide ads say grubs are the ultimate evil. Well, sure!
Advertisers demonize grubs
so we will buy a product --
chemicals to kill grubs. The people who pay for those ads have no
reason to tell you a grub can have a good side.
Or that it takes at least
grubs per square foot to do real lawn damage.
Right: Just as a caterpillar changes within chrysalis or
cocoon to emerge as a butterfly or moth, a grub rests inside a pupa
case then comes out as a beetle.
Beetles are insect hunters
Rove beetles, ground beetles and others are very effective
insect hunters. Among their targets are harmful caterpillars,
including lawn eating species such as sod webworm.
There are 3,100 rove beetle species
(right) in North America, all of them beneficial predators
of other insects. None are harmful in human or agricultural
There are 1,700
species in North
of the most
commonly occurring beetles are in this group. Most travel
ground, are very fast moving, are active at night and prey
cutworms, snails, caterpillars, maggots, cankerworms,
beetle larvae, etc. Most are shiny and primarily black. A
few may eat
vegetable matter and may sometimes cause trouble in a
Left: We bet you've run across ground beetles
like this one as you garden. They're fast moving, hunters, night
creatures who shy from the light.
261 species of checkered beetles in North
America are very important predators of wood-boring beetles.
Ladybugs are beetles and there are 400 species of
lady beetle. All but 6 ladybug
species are very effective predators of soft bodied pests such
as aphids, scale, mites and mealybugs. In their young form
beetles are already hunters, not grubs but above ground
stalkers. However, like grubs, baby ladybugs are often killed for
their looks -- we hear them described as segmented dragons, fat
alligators or, simply, "Eeew!"
Beetles improve soil
Every beetle, even a lawn-root eater, also consumes general
organic debris. This returns nutrients to the soil and creates
humus that enriches the soil.
Every subterranean grub digs sidewise through the ground and also
up and down in response to changing temperature and moisture. Every
move a grub makes aerates the root zone and helps aggregate mineral
grains into crumbly, moist soil. (In the lawn grub life cycle chart you can
see all the up-and-down action in the development of each
Beetles are critical food for birds
Many birds and animals hunt grubs, which are an essential, high
protein food source for their young. Many baby songbirds would
perish if not for grubs.
Benign or neutral
Right: Many beetles, such as the North American bumble
flower scarab beetle, are not harmful to plants or other
animals/insects. They're neutral or benign in effect. This one
looks enough like a bumblebee in its motion and setting that you
may have seen one but did not realize you were seeing a
Always a few bad guys in every bunch
Some white grubs eat grass roots and can harm a lawn if their
population gets out of hand. If you find six or more large white
grubs under every flap of sod you turn, you may have this problem.
Fewer than this, stop worrying about grubs.
If you must fret about grubs, focus on snout beetle species, so
called because the head has a snout-like appendage. Almost all
snout weevils are plant eaters and the grubs are quite small
(below, at their largest, the size of plumped grains of
rice). This group includes strawberry root weevil and
black vine weevil, which can do really serious damage to a garden.
(More about black vine weevil in What's Coming Up issue
67 and issue
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