North Idaho landscaping guide and educational resource featuring seasonal timing context supporting stronger maintenance habits in Post Falls, Coeur d'Alene, and North Idaho
May – June · Growing Season Setup

Watch for aphids and spider mites on ornamentals

Both aphids and spider mites thrive in the warm, dry conditions of an Idaho May and June. Early detection — before populations explode — makes all the difference between a quick spray and a lost plant.

Why This Matters in North Idaho

North Idaho's warm, low-humidity summers are ideal for spider mite population explosions on junipers, arborvitae, and roses. Aphid pressure spikes on new growth in May, particularly on Native Elderberry, Viburnum, and rose species common in Kootenai County landscapes.

Step-by-Step

  1. 1

    Scout weekly during May and June

    Physically look at the undersides of leaves on susceptible plants (roses, viburnum, lilac, fruit trees). Spider mites leave a telltale fine webbing and cause stippled, bronze-colored leaf surfaces. Aphids cluster on new growth tips.

  2. 2

    Use the shake test for spider mites

    Hold a white piece of paper under a branch and shake firmly. Spider mites will drop onto the paper as tiny moving specks — barely visible but identifiable as alive.

  3. 3

    Water blast for light aphid pressure

    For minor aphid infestations, a strong stream of water from your hose (bottom of leaves) knocks populations off effectively. Repeat every 3–4 days to break the reproduction cycle.

  4. 4

    Apply insecticidal soap for moderate pressure

    Insecticidal soap (not dish soap) kills soft-bodied insects on contact. Spray thorough undersides of leaves in early morning. Reapply after rain. Safe for beneficials once dry.

  5. 5

    Miticide for confirmed spider mite colonies

    Once mites have webbing established, insecticidal soap is not sufficient. Use a labeled miticide (e.g., bifenazate or spiromesifen). Rotate chemistries if treating twice to prevent resistance.

Pro Tips from 20 Years in the Field
  • Avoid broad-spectrum pesticides (pyrethroids) for aphids — they also kill the beneficial insects (ladybugs, parasitic wasps) that naturally control aphid populations. You often make the problem worse.
  • Stressed plants are more susceptible. Mite and aphid pressure on plants that are drought-stressed, over-fertilized with nitrogen, or in poor soil is almost guaranteed.
  • Ants "farm" aphids for their honeydew excretions — if you see ants climbing ornamentals in numbers, check for aphids.

When to Call LandscapePros

Persistent pest problems, suspected disease (versus pest), or large-scale landscape pest management is best evaluated in person. Our crews can identify the issue and recommend the appropriate IPM approach.

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May – June

Watch for aphids and spider mites on ornamentals: Questions We Get Asked

North Idaho's warm, low-humidity summers are ideal for spider mite population explosions on junipers, arborvitae, and roses. Aphid pressure spikes on new growth in May, particularly on Native Elderberry, Viburnum, and rose species common in Kootenai County landscapes.

Get Seasonal Tips
How do I tell the difference between aphids, mites, and fungal disease?
Aphids are visible to the naked eye, clustered on new growth, often with sticky honeydew and sooty mold beneath. Spider mites are not, but they show as fine stippling and webbing, usually starting on the underside of leaves. Fungal disease shows as discrete spots with defined margins and a colored halo. When in doubt, rub a leaf over white paper — moving specks means mites.
Does spraying soapy water actually work?
For a light infestation, yes, and it is the right first move — you avoid killing your pollinators and the lady beetles that are already working for you. Use actual insecticidal soap, not dish soap, and spray the undersides of leaves where eggs live. Repeat every five to seven days for three cycles, because soap kills on contact and does nothing to eggs already laid.
Why do my plants get spider mites every year?
Hot, dry, dusty conditions. Mites thrive in the July heat when plants are already stressed and the lawn is a reservoir of dust. The most effective prevention is keeping plants adequately watered and rinsing foliage during hot dry spells — both of which reduce the conditions mites need to explode.
When is a pest problem serious enough to call a professional?
When it is on a large planting, when you cannot identify what is causing it, or when plants are already visibly declining. Pest identification is the hard part, and treating the wrong cause wastes a season and kills beneficial insects along the way. North Idaho also has specific invasive pests where treatment choices are regulated, so identification genuinely matters.
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