CORVALLIS, Ore. — You see aphids sucking the life from rosebuds, flea beetles chomping cauliflower and cabbage butterflies flitting through the garden.
Your first instinct may be to reach for a spray can — but Heather Stoven, an associate professor of practice and horticulturalist with Oregon State University Extension Service, urges a more strategic approach.
“Assess the damage,” Stoven said. “Do an evaluation. Try to see how many insects there are and if they’re spreading. Be sure to identify the insect so you know what you’re dealing with. That way you can most effectively manage the situation.”
Not all insects are enemies
Insects are part of a healthy garden ecosystem, and many beneficial species feed on pests. Often, these “good bugs” help keep harmful insects in check. Stoven recommends practicing integrated pest management (IPM) — an approach that uses multiple strategies to monitor and control pests with the least environmental impact.
Start by walking through your garden regularly to catch problems early. Determine how much damage you can tolerate as beneficial insects do their job. If pest numbers increase beyond your comfort level, begin with the least toxic methods.
For example, spray aphids off plants with a strong stream of water or use floating row covers to prevent cabbage butterflies from laying eggs. Understanding insect lifecycles is key: soft-bodied larvae are easier to control than hardened adults, and squashing egg masses can prevent infestations from ever taking hold.
Start with the gentlest control methods
Physical and cultural controls are often effective and safe:
- Pick pests off by hand and drop them in soapy water.
- Wash insects away with a hose.
- Use traps and row covers to keep pests out.
- Encourage natural predators by planting flowers like cosmos, dill, fennel, yarrow and coreopsis.
If infestations continue, consider biological controls such as beneficial nematodes or Bacillus thuringiensis (Bt). Chemical controls should be a last resort. Even “natural” pesticides can harm pollinators, pets or humans. Always read the label, confirm it targets your specific pest and follow application instructions precisely.
Garden health reduces pest pressure
A thriving garden is less vulnerable to insect outbreaks. Stoven recommends these cultural practices:
- Water properly — neither under- nor overwater.
- Space plants appropriately to allow airflow.
- Prune regularly to prevent overcrowding.
- Avoid overfertilizing, which encourages tender new growth that insects love.
“Properly grow plants,” Stoven said. “Keep them healthy and they’ll be able to fight off pests much easier.”
Five common garden pests — and how to manage them
Aphids
One of the easiest pests to control. Stoven suggests:
- Spraying them off with water
- Squishing them by hand
- Attracting natural predators like lady beetles by planting flowers such as marigolds, echinacea, dill and yarrow
Azalea lace bug
This pest also affects rhododendrons and can be difficult to manage. Stoven recommends:
- Removing and replacing heavily infested shrubs with resistant varieties
- Using horticultural oils or soaps — with full coverage
- Avoiding systemic insecticides when pollinators are present
For more, refer to the Extension publication Azalea lace bug: Biology and management in commercial nurseries and landscapes.
Cabbage white butterfly
Though lovely, these butterflies lay eggs that become hungry caterpillars. Stoven suggests:
- Using floating row covers to prevent egg-laying
- Keeping covers in place throughout the growing season
- Hand-picking larvae from the underside of leaves
Cucumber beetles
These pests nibble cucumbers but mainly damage foliage. Stoven advises:
- Tolerating minor damage if plants are well established
- Using row covers early in the season
- Choosing pesticides labeled for food crops only if necessary
Flea beetles
These tiny pests feed on a wide range of crops. Tips include:
- Planting early so crops outgrow early-season beetle pressure
- Using row covers
- Interplanting with radishes, which act as a decoy
- Spraying only if infestations become severe — and only on the radish tops to protect nearby crops
Get help from OSU Extension
For insect identification and personalized pest control advice, contact a Master Gardener volunteer at your local Extension office or use Ask Extension, a free online tool where you can submit photos and questions. Master Gardeners and Extension experts are ready to help.
Previously titled Know garden pests before deciding on a path to control
