7 Common Garden Pests in Colorado (and How to Manage Them)

You’re not the only one looking forward to getting out into the garden in spring. The pests are already getting ready to pounce on your favorite plants. While we can’t blame them, we also can’t abide by them in our herb and vegetable gardens, our fruit trees, or on our flowers.

You want to be careful about spraying insecticides that endanger the beneficial bugs in your garden. Parasitic wasps and green lacewings will help control the pest population if you let them. Here are the seven common pests you want to get rid of in your garden.

1. APHIDS

These tiny sap-sucking insects come in all different colors, including light green, white, black, brown, gray, and yellow. Their soft, pear-shaped bodies can appear waxy or woolly. With their long antennae, these creatures would be adorable — if they weren’t so destructive. Aphids multiply quickly, and when large clusters of them inject their toxic saliva into plants, you’ll see leaves curling or turning yellow. You also leave a sticky “honeydew” substance on your plants, which can attract other insects, such as ants.

How to get rid of them

  • First, try wiping off the affected leaves. If you have an infestation, try spraying the leaves with a mixture of water and dish soap. You may need to re-treat the leaves every few days for a couple of weeks.
  • Lady beetles (ladybugs) love to eat aphids, so buy a colony, either online or at your local nursery, and release them into your garden.
  • Plant some catnip near your affected plants, as the herb repels aphids. Keep in mind. You may be overrun with neighborhood cats.

2. WHITEFLIES

These tiny winged insects hang out in clusters underneath leaves. Somewhat triangular, they’re related to aphids and active during the daytime. They like tomatoes and bell peppers, so check these plant leaves carefully and often. If you see them flying off after you shake the leaves, it’s time to start blasting with the garden hose.

How else to get rid of them

  • Spray a mixture of dishwashing liquid and water early in the morning or late in the day. A good squirt of soap into a gallon of water is the right ratio.
  • Use a handheld vacuum every few days to remove them from your plants.

3. TOMATO PSYLLIDS

Psyllids extract plant juices and excrete small waxy beads that resemble table sugar. According to experts at the University of California-Davis, psyllids can develop quickly during warm weather and do a lot of damage fast. A slight yellow or purple discoloration along the mid-rib and edges of the top leaves of tomato plants is the first sign of infestation.

 What you can do

  • Mature plants have a better chance of survival. Plant tomatoes, peppers, and eggplants in early spring. This allows the crop to mature before psyllids attack them in the heat of summer.
  • Remove old plantings from the garden, and compost or place them in the trash to prevent the next generation of psyllids from hatching.
  • Sprays containing neem oil can help control a variety of garden pests, including tomato psyllids.

4. FLEA BEETLES

These small bugs with large back legs come in numerous colors, including striped, black, bronze, brown, metallic, or bluish-gray. Small white larvae feed on the roots of newly planted seedlings. Adult flea beetles become active in early spring, feeding on plant leaves and stems.

What you can do

  • Adult flea beetles will attack the tallest, earliest crops available. Plant a sacrificial crop, such as radish, before you plant your main crop. Once beetles start feeding, spray with a pesticide labeled for treating flea beetles.
  • Use screening to protect the seedlings, but remove barriers before the flowers come up so that pollinators can reach the plants.

5. GRASSHOPPERS

These bouncing bugs can gobble up half their body weight in a single day. Small numbers of them tend to move on, but if your garden has become home to a large number of grasshoppers, there are some steps you can take to protect your plants:

  • Sprinkle boric acid along the garden edges. This also kills ants and aphids.
  • Crush half a dozen garlic cloves and let them sit in 1/2 cup of mineral oil overnight. Add 5 cups of water to the mixture and strain it into a spray bottle.
  • Add two crushed bulbs of garlic to 10 cups of water and bring to a boil. Allow this to sit all night before spraying the mixture in your garden.

Grasshoppers will search for grassy areas of your yard. As you prepare your lawn for spring, you’ll discourage them by mowing, watering, and fertilizing.

6. TWOSPOTTED SPIDER MITES

These tiny bugs may be brown, orange-red, green, greenish-yellow, or almost translucent if you can see them at all. They thrive in hot, dry weather, spinning fine strands of webbing on host plants, where they lay their eggs. When they feed on leaves, a graying or yellowing occurs. When they attack your flowers, you’ll notice a burned appearance.

What you can do about them

  • Hosing off plants with a forceful jet of water can physically remove and mites. You also want to clean off the dust that collects on foliage and interferes with mite predators.
  • Keep plants adequately watered to avoid drought stress, which can lead to spider mite outbreaks.

Insecticidal soaps and oils are effective and less toxic to pets and people than chemical pesticides

7. Ticks

Fortunately, the Denver Metro area is not home to the tiny parasites that cause Lyme Disease. However, we do have 27 other varieties of ticks, and something called Colorado tick fever to be aware of after spending time outdoors. The best way to avoid being infected is to check yourself after spending time outdoors so you can remove any hitchhikers.

The Colorado State University Extension is a great resource for learning more about anything that’s damaging your plants, and you can email them questions if you don’t find answers yourself. Happy gardening!


Richard Gillespie is an exterminator whose interest in household and landscape pests began as a child when he would crank up the radio to hear “I Don’t Like Spiders and Snakes.” He prides himself on practicing humane and eco-friendly pest control unless he finds a rat. Then, all bets are off.