5 Harmful Garden Insects and How to Eliminate Them

Written by Naomi Meza


Posted on April 11 2019

As a gardener, it may seem like everything and anything is a threat to the wellbeing of your plants.

This is especially true at the start of the growing season when warmer weather invites hungry insects to come out to play.

But oftentimes, we notice our damaged plants before spotting the bug responsible.

How quickly you realize your plants are infested can mean the difference between saving them or calling it quits.

Read on to learn of a few of the most common harmful garden insects, how to identify them and more importantly, how to remove them from your garden and prevent them from appearing in the first place.

1. Tomato Hornworm 

Tomato Hornworm Infestation

First up on our list is the Tomato Hornworm. As its name suggests, it preys on tomato plants, but it's also known to destroy potato, pepper, eggplant and tobacco plants.

What Does it Look Like?

The Tomato Hornworm is tough to spot because it’s a pro at camouflage. It is likely one of the largest caterpillars you’ll see in your garden.

Its green body is 3 to 4 inches long with several diagonal, white stripes all along its back. It also has a black or red horn protruding from its rear.

This is while the insect is young.

Adults on the other hand, are large moths that are gray or brown with white v-shaped lines on the rear wings and orange or brown spots along the body.

These lay eggs on your plants that become the Hornworm caterpillars.

How Do I Know it’s in My Garden?

  • Dark green droppings on plant foliage and the ground surrounding your plants.
  • Wilted leaves and missing stems.
  • Leaves with large holes and severe defoliation.
  • White cocoons hanging from your plants.

Tip: If you spray the leaves with water, the caterpillars will thrash around and give away their hiding spots.

How to Eliminate Them

  • Remove the worms by hand and drop them into a bucket of soapy water.
  • Ladybugs, lacewings and braconoid wasps can attack the eggs to prevent further infestation. You can attract them to your garden by planting dill and/or fennel.
  • Use an organic pesticide like BT (Bacillus Thuringiensis)



  • Till your garden at the beginning and end of each gardening season to kill the pupae that overwinter in the soil and eventually lay eggs on your plants.
  • Plant basil, dill and marigolds to not only deter them, but to encourage beneficial insects to live in your garden.


2. Mealy Bugs

Mealybug Garden Infestation

Mealybugs are most commonly found in warmer growing climates. Although they can infest outdoor gardens, they are especially known to destroy indoor plants and those in greenhouses.

What Do They Look Like?

Mealybugs appear as soft-bodied, small, white clusters on the leaves, stems and fruit of your plant and blanket themselves in cotton-like/waxy substance.

Adult females are wingless and are usually the ones that you spot on your plants.

Adult males however, are even smaller than females, are rarely seen and have two wings and two tail filaments.

Newly hatched mealybugs called nymphs or crawlers, are orange to pink in color and don’t excrete wax until after they start feeding.

How Do I Know They’re in My Garden?

  • Honeydew and wax excretions are found on plant foliage.
  • Reduced plant vigor caused by mealybugs sucking out sap.
  • Leaf drop and yellow leaves.
  • Small balls of cotton wool on undersides of leaves.


How to Eliminate Them

  • For light infestations, spraying down the bugs with water should be enough to remove them completely.
  • Spray plants with insecticidal soaps, horticultural oils or Neem Oil.
  • Soak a cotton swab in rubbing alcohol and apply directly to the clusters of bugs.



  • Inspect new plants for infestation before bringing them home from nurseries and garden stores.
  • Clean all containers, greenhouses and other areas where you keep your plants.
  • Space out your plants to promote air circulation.
  • Lower the temperature of greenhouses during cooler months.


3. Aphids

Aphid infestation

Aphids are known to attack plants of all kinds especially food and ornamental plants.

What Do They Look Like?

Aphids are small, pear-shaped insects that range from green, red, brown, black and yellow. They have small tubes called cornicles protruding from their rear.

How Do I Know They're in My Garden?

  • Twisted, curled or swollen leaves and stems.
  • Decreased growth rate of plants.
  • Low Yields
  • Honeydew substance on leaves and stems.
  • Black Sooty mold


How to Eliminate Them

  • Release ladybugs in your garden to eat the aphids.
  • Dislodge them from leaves with cold water. (Best for light infestations only)
  • Apply Diatomaceous Earth to infestation sites.



  • Plant Catnip, Nasturtium, garlic and chives in your garden.
  • Attract beneficial insects to your garden.


4. Spider Mites

Spider Mite Infestation

Spider mites are common in North America and attack both indoor and outdoor plants and especially those in greenhouses. You’re likely to find them on eggplants, tomatoes, melons, strawberries and beans.

What Do They Look Like?

Adults are reddish brown or pale in color, oval shaped and very small. Younger mites resemble the adults but are even smaller.

How Do I Know They're in My Garden?

  • White or yellow spotting on leaves.
  • Webbing and silk threads on undersides of leaves.


How to Eliminate Them

Isolate infested plants and remove infected leaves. Place leaves in a sealed bag, throw them out or burn them.

  • Reduce air flow between plants by placing them close together.
  • Make a 1:1 mixture of alcohol and water and spray the leaves.



  • Water your plants since spider mites don’t like moist conditions.
  • Dust plants regularly.
  • Clean the leaves with a damp cloth. Larger plants can be sprayed.
  • Place a humidifier near your plants to keep the environment moist.


5. Flea Beetles

Flea Beetle Infestation

This bug attacks various kinds of plants, but vegetables are the most susceptible. They are the most threatening at the start of the growing season as they emerge from their dormancy.

What Do They Look Like?

Flea beetles are small and shiny with large rear legs. They vary from black to tan and are solid or spotted in color depending on the species.

How Do I Know They're in My Garden?

  • Shotholes in leaves, especially young seedlings.
  • Damaged leaves resemble lace-like patterns.
  • Beetles will jump when disturbed.


How to Eliminate Them

  • Homemade spray: 2 cups rubbing alcohol, 5 cups water, 1 tablespoon liquid soap.
  • Dust plants with plain talcum powder.
  • Place sticky traps throughout garden rows to capture adult beetles.



  • Delay transplanting or planting by a few weeks at the start of the growing season.
  • Till the garden in the Fall to bring hiding flea beetles to the surface.
  • Plant catnip and basil to repel them.


Grow With Greenway for Harmful Insect Prevention

Unfortunately, at some point on your growing journey, you may deal with pesky insects that do more harm than good.

While using any of the above preventative methods may help repel these bugs completely, it's always great to ensure your plants are strong and healthy to begin with.

Supplying your plants with the proper nutrients they need from the get-go can build their immune system so they're strong enough to fight off bug infestations before they get out of hand. Browse our shop for nutrients that will support your plants' healthy growth.

Harmful insects won't stand a chance!


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