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How-To Guide

How to Scout Vegetable Garden Pests Before You Spray

One chewed leaf is not an emergency. Inspect both sides of leaves, identify what is present, decide whether damage is increasing, and protect the predators already working for you.

Gloved hands holding a magnifying glass to the underside of a large vegetable leaf, with a yellow sticky trap behind
Illustration: scouting a leaf underside with a lens. Not a photograph. Not a San Diego bed.
Now

Scout the same route each week, including leaf undersides.

Why

Broad sprays used before identification can kill natural enemies and turn a small problem into a repeating one.

Next

Identify first; physical controls before a narrow, labeled product.

Kit

  • 10× hand lens
  • Phone camera or notebook
  • Gloves
  • Hose nozzle with a firm water stream
  • Small container for an identification sample
  • Optional lightweight row cover
  • Any pesticide label before purchase or use
Illustration of an IPM scout loop: look, identify, wait, act
Illustration: look, identify, wait, act. Not a photograph. Not a San Diego bed.

Do this

  1. Scout the same route each week

    Check growing tips, lower leaves, leaf undersides, stems, flowers, and nearby weeds. Compare healthy and damaged plants.

    UC MG.

  2. Separate pest, damage, and beneficial

    Photograph the organism and the symptom together. Look for eggs, cast skins, sticky honeydew, frass, webbing, or tunneling.

    • Do not assume every insect caused the damage.
    • Keep lady beetles, lacewings, syrphid larvae, and parasitoids working.
    • Use UC IPM identification help when uncertain.

    UC MG.

  3. Decide whether action is needed

    Ask whether new damage is increasing, whether the crop is young or nearly harvested, and how much loss you can accept. A vigorous squash can tolerate more chewing than a newly emerged seedling.

    UC MG.

  4. Fix growing conditions first

    Correct water stress, crowding, weeds, and diseased debris. Exclude predictable pests with row cover before they arrive, but remove covers when a fruiting crop needs pollination.

    UC MG.

  5. Use physical controls

    Hand-pick hornworms and snails, prune a heavily infested leaf when the plant can spare it, and dislodge aphids with water while supporting the stem. Recheck before escalating.

    UC MG.

  6. If necessary, choose a narrow control

    Use a product only when the pest and edible crop appear on the label. Follow every rate, timing, protective-equipment, pollinator, temperature, and harvest-interval direction.

    UC IPM.

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