Insects can be benefical to boosting budding and blooming gardens

Published on Wed, Aug 28, 2013 by Steve Guntli

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When insects are slithering and crawling over every inch of your garden like mini movie monsters, the instinct to squish the creepy-crawlies may be strong, but think twice before you bring down the boot – the key to a thriving garden is knowing how to encourage helpful bugs as much as you discourage the harmful ones.

Kelle Rankin-Sunter is the founder of Blaine Community Orchards for Resources and Education (C.O.R.E.), an organization 
that encourages the growth of fruit- and vegetable-bearing plants. She said that although it may seem counterintuitive, the best way to keep pests out of the garden may be to stop using pesticides altogether, since they can kill beneficial bugs as well. 

But even the most carefully tended gardens aren’t immune to the occasional intruder.  

As the weather grows colder and wetter, some decidedly unwelcome visitors will be popping in more frequently: slugs. These slimy creatures thrive in wet climates and usually come out at night. They eat soft plants like flowers, lettuce and strawberries, chewing gaping, ragged holes through leaves and leaving an unsightly trail of slime in their wake. If left unchecked, these pests can ravage a garden. Slugs are too large for other insects to combat effectively, so unless there are ducks or chickens on hand to eat them, gardeners will have to deal with slugs themselves.

Mike Delancey, the retail green goods manager at Van Wingerden Garden Center, helps customers combat garden slugs all the time. 

“Slugs are really prevalent here, but you don’t see them much during the day because they hate the sunshine,” he said. “You
 get less pressure from slugs in the summer, but as the weather gets cooler, they come out in force.” 

There are several repellants that can keep slugs at bay. Copper creates a reaction in slugs akin to electric shock, Delancey said, so lining planters with copper tape will help repel the slimy pests. Surrounding the affected plants with diatomaceous earth, a soil blend composed of fossilized marine life, can also deter these unwelcome visitors from visiting. 

While these methods won’t completely decimate your local slug population, it will help keep them away from particularly vulnerable plants. To really eliminate slugs, Delancey recommends slug bait, such as Corry’s Slug Bait or Deadline, which paralyzes the nocturnal slugs until the sun comes out to cook them. He cautioned that some slug baits can be harmful to pets, though, so Delancey suggests leaving the bait in dark, hard-to-reach places, such as beneath an old sheet of plywood or under a porch. Classic slug disposal methods, such as salt, are effective but can damage your plants and leave an unsightly mess. 

But, he said, one of the best weapons against slugs may already be in your refrigerator. He suggests using beer to dispose of the slimy monsters.

“Beer is an effective way of eliminating slugs,” Delancey said. “The secret with beer is to make a little saucer and fill it with some sort of inexpensive beer, bury it in the ground so the beer’s exposed. Slugs will fall in and drown. They drown, but they drown  happy.”

Not all slug-control options have to be fatal, though. Rankin-Sunter recommends hand-controlling slugs by simply picking them up and moving them. She throws any slugs she comes across onto her compost pile, so they can still break down refuse and provide a useful service for her yard.

Slugs may be the heavies, but they’re far from the most common garden pest. The biggest offender, in Washington or 
anywhere else in the U.S., is the aphid, according to Organic Gardening Magazine. Aphids are tiny, pear-shaped insects with dozens of varieties that feed on just about anything. 

These year-round pests suck the juices from plants with their long nose-like protuberances, which can cause curled or cupped leaves. While aphids rarely destroy plants outright, they can eat through portions of the plant and produce a large amount of sticky residue called “honeydew,” which is both unsightly and can lead to damaging fungal growth.

“The good thing about aphids is they’re really easy to control,” Delancey said. “There are several organic insecticide soaps that work extremely well. Even a strong stream from a hose knocks them onto the ground, where black garden beetles will just decimate aphids. They are voracious eaters of aphids.”

Here’s where the good guys come into play – there are a wide variety of fearsome-looking pest-hunters that should make you think twice about squishing your garden’s bugs willy-nilly. The aforementioned black beetles are typically 3/4 inch long and can be found in most climates in the U.S. year-round. Delancey says that a lot of people squish them on sight, but they can keep the aphid population in check. 

Another frequently crushed helper is the spider. While sometimes frightening in appearance, spiders are some of the most efficient predators in the garden. There are very few species in western Washington that are considered dangerous to humans, since deadly varieties like the brown recluse prefer warmer, drier climates, but black widows do occasionally take up residence in woodpiles and other dry, dark areas.

Spiders and praying mantises certainly look the part of the vicious predator, but appearances can sometimes be deceiving. The aphid’s chief predator is actually the cute, red-and-black spotted ladybug. Ladybugs have an insatiable appetite for aphids, mites and other tiny pests. Even ladybug larvae, which Delancey says resemble “orange and black alligators,” chow down on aphids. And, since ladybugs have no interest in eating any vegetation, they can safely roam the garden cleaning up pests. They are common insects in most parts of the world, and they can also be purchased at many home and garden stores. However, ladybugs are less effective as the weather grows colder, and usually go dormant in the winter. 

But that doesn’t mean your plants have to fend for themselves. A little TLC can go a long way in garden care since maintaining a healthy garden is a lot like maintaining a healthy body, according to Rankin-Sunter.

“If we get run-down or stressed out, we don’t take care of ourselves and we’re much more inclined to get sick,” she said. “Plants are the same way. If they aren’t getting the proper amount of water or nutrients, they will be more vulnerable to bugs.”

Ultimately, the healthier your plants are, the greater their resistance to infestations will be, Rankin-Sunter said.

“Bugs aren’t necessarily ‘bad’ or ‘good,’” she said. “Those aphids attacking your plants are just filling their niche, and acting as a symptom of a plant that’s not well.” 

For more information, visit Blaine C.O.R.E.’s website at