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Garden Bugs: The Good and the Bad

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Garden Bugs: The Good and the Bad

A garden is not only a haven for plants but also a home for insects. Many are beneficial, “the good”, but there are those that are detrimental, “the bad”. A common gardening belief is that slow-moving bugs (such as slugs and aphids), feed on plants, while fast-moving ones (ladybugs and black beetles, for example), feed on other unwanted insects. This is generally correct, but it’s not a perfect rule. Learning to identify the good insects and permitting them to inhabit your garden will help keep your plants healthy.

Ladybug on green leaves

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The Good: Beneficial Garden Insects



Lacewing (suborder Endopterygota or Neuropterida)

Benefit: Feeds on a variety of small soft insects. Larva is known as the “aphid lion” because of its propensity to prey on these insects

Attraction: Nectar and pollen-rich plants


Ladybug (Hippodamia convergens)

Benefit: Voracious aphid eater

Attraction: Particularly seems to like nasturtium (Tropaeolum), lamb’s ear (Stachys byzantine), morning glory (Ipomoea) and yarrow (Achillea)


Assassin Bug (Reduviidae)

Benefit: Feeds on a variety of pests, including caterpillars, leafhoppers and mites

Attraction: Found naturally in most gardens

Honey bees on a sunflower

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Ground Beetle (Carabidae)

Benefit: Nocturnal feeder that eats most ground insects, including slugs, snails, cutworms and caterpillars

Attraction: Provision of daytime shelter beneath stones, logs, mulch, etc.


Soldier Beetle (Cantharidae)

Benefit: Feeds on aphids, cucumber beetles and caterpillars

Attraction: Hydrangea, milkweed (Asclepias), goldenrod (Solidago)


Praying Mantis (Mantis religiosa)

Benefit: Feeds on flies, aphids, moths and caterpillars

Attraction: Provision of winter shelter — remove their cocoons from goldenrod plants in fall and strategically situate in the garden where they will survive the cold


Honey Bee (Apis mellifera)

Benefit: Industrious pollinator, as are other bees and wasps

Attraction: Nectar and pollen-rich plants

Great black wasp

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Tachinid Fly (Tachinidae)

Benefit: Parasitic insect that lays eggs on hosts, such as caterpillars. Emerging larva feeds on and eventually kills host.

Attraction: The blooms of lemon balm (Melissa officinalis), parsley (Petroselinum crispum) and sweet clover (Melilotus officinalis)


Parasitoid Wasp (suborder Apocrita)

Benefit: Feeds on aphids, caterpillars, grubs and other pests

Attraction: Small-flowered plants, such as herbs

Earwig

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The Bad: Detrimental Garden Insects



Aphid (Aphididae)

Detriment: Sucks the juice from the leaves and stems of a variety of garden plants, thereby weakening plant. Transmits viruses to plants. Can produce dozens of generations each growing season. Commonly called “plant lice”.

Deterrent: Seems to avoid allium, coriander (Coriandrum sativum) and nasturtium (Tropaeolum spp.). Can often be controlled using a jet of water to blast them from the infested plant. Also try homemade soap spray (e.g. 2 tbsp. dish detergent mixed with 1 gal. warm water).


Earwig (Dermaptera)

Detriment: Nocturnal feeder that likes marigold (Calendula spp.), clematis, gladiolus, aster and many others. Hides during the day in small crevices, under plant debris, etc.

Deterrent: Keep soil debris free. Bait with saucers of fish oil or stale beer and empty trapped earwigs into a bucket of soapy water to kill them.


Slug and Snail (Gastropoda)

Detriment: Both are mollusks, rather than insects. Snails are slugs that, in the adult stage, have a shell. Hides during the day under rocks, logs, etc. and feeds at night on lower leaves of a variety of flowers and vegetables.

Deterrent: Keep garden debris free and thin plants for good air circulation. Look for slimy trails, which signal infestation, then hand pick. Sprinkling salt over them works as well, but beware of how much salt is getting into the soil. Traps and dry barriers have also proven successful.

Ant

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Japanese Beetle (Popillia japonica)

Detriment: Spawn from grubs and are a pest in all forms of their life cycle. They are voracious eaters of everything from grass roots to plant leaves and fruit.

Deterrent: Has a fondness for grass and lays its eggs in lawns midsummer. Use beneficial nematodes (microscopic soil-dwelling worms that can be purchased at many garden supply centers) to treat when certain there is a large population present. Floating row covers can help.


Lily Leaf Beetle (Lilioceris lilii)

Detriment: Colorful red insect that feasts on true lilies (Lilium spp.), not daylilies (Hemerocallis spp.)

Deterrent: Must hand pick adults and larvae. If they have burrowed into the bulb, crush them using the end of a coat hanger.


Mosquito (Culicida)

Detriment: Transfers diseases to both humans and animals.

Deterrent: Remove standing water from yard. Put netting over rain barrels.


Cabbageworm / White Cabbage Moth (Pieris rapae)

Detriment: A pest of a wide variety of plants, particularly species of Brassica oleracea (cabbage, cauliflower, broccoli, kale, etc.). Damage is usually cosmetic.

Deterrent: Parasitoid wasps are one of its chief enemies. Using a floating row cover can also help control it.


Ants (Formicidae)

Detriment: Can damage plants roots due to its tunneling habit. Some species protect aphids from enemies and carry them to new plants. More of a nuisance inside the home than in the garden.

Deterrent: Sprinkle corn meal, which ants cannot digest, around the hills. Alternatively, pour a few gallons of boiling water on hills.

Rose showing signs of pest damage.

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Controlling Garden Pests


It’s no secret that avid gardeners spend much time cultivating their gardens, so it’s no wonder they become discouraged when they discover that insects have disfigured their beloved plants. Minor damage, such as small incisions on leaves, is normal and usually doesn’t threaten the plant’s health. However, larger-scale problems often require intervention. Gardeners basically have two options — using chemical means of control or seeking non-chemical alternatives.

Plant leaves showing signs of pest damage.

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Chemical Controls


This includes the use of pesticides, in this case, insecticides. However, in many regions, environmental concerns have resulted in usage bans on cosmetic pesticides in the home garden. These concerns include, but are not limited to, the fact that insecticides can kill off all garden insects, not just those considered detrimental. Also, chemicals used to treat one pest can inadvertently kill or harm other wildlife. Finally, insects can develop a resistance to pesticides. Fortunately, many solutions can be found without having to reach for chemicals.

Container filled with marigold blooms.

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Non-Chemical Controls



  1. Attract beneficial insects to the garden. Do so by:

    • Maintaining a pesticide-free garden

    • Growing plants that beneficial insects like

    • Growing garden plants that will provide a continuous cycle of summer blooms

    • Growing plants that vary in height to attract different insects

    • Adopting a selective weeding practice, which entails leaving a few weeds that are attractive to some beneficial insects, such as dandelion (Taraxacum), clover (Trifolium), and even goldenrod (Solidago)
Floating row cover placed over plants

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  1. Attract birds to the yard by putting up feeders, baths and houses. Birds are excellent at bug eradication and pleasant to have in the garden.

  2. Experiment with companion planting to determine whether it works in your garden. For example, planting garlic around roses may deter aphids and resulting black spot. There is no scientific evidence to prove companion planting works, but many gardeners attest to its benefits.

  3. Try natural remedies you can make in your kitchen such as the aforementioned soap spray (see section on aphids) and different vegetable- and herb-based sprays, such as lemon or garlic sprays.

  4. Walk through your garden daily, armed with a container of soapy solution, and spray infested plants. Hand pick pests that aren’t deterred by the spray.

  5. Practice good garden sanitation to eliminate pest havens.

  6. Use floating row covers to prevent pests from reaching plants.



Ron Rossini