Good guy grubs

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We have some grubs. Good! 

If we find a grub or two every time we dig, we are not alarmed at all but glad.
Why? Because:
    - Grubs become beetles, and there are
        thousands of species of beetles.
    - There are probably hundreds of beetle species
        in every average, healthy North American garden.
    - The majority of beetles eat other insects or
        break down dead things that would otherwise stack up
        like trash during a collection strike.
    - It's tough to know one grub or pupa from another,
        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 everywhere?!


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?

BeetlePupaN5243s.jpg GrubChafrDimen0848S.jpg

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
6 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.roveBeetlExtS.jpg

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 terms.

GroundBeetleN7836s.jpg  There are 1,700
  ground beetle
  species in North
  America. Some
  of the most
  commonly occurring beetles are in this group. Most travel on the
  ground, are very fast moving, are active at night and prey on
  cutworms, snails, caterpillars, maggots, cankerworms, other
  beetle larvae, etc. Most are shiny and primarily black. A few may eat
  vegetable matter and may sometimes cause trouble in a garden.

   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 (below) these 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 grub.)

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 beetle.

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 139.)

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