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Pest Management — Bay Area


Pest Management — Bay Area (Sunset 14–17; USDA 9–10)


Integrated Pest Management in one page (how we work)


  • Prevent first: healthy soil, correct water/airflow, rotation, resistant cultivars, sanitation. IPM as prevention + monitoring + layered controls; pesticides only if needed, least-toxic, label-directed.

  • Identify correctly: treat signs/symptoms, not guesses; mis-ID wastes time and harms beneficials.

  • Monitor weekly: underside of leaves, new growth, and soil surface; use sticky cards for flying pests (monitoring first, not mass control).

  • Act in layers: cultural/physical → biological (protect natural enemies) → least-toxic products (oils/soaps/Bt/iron-phosphate), only as a last layer.


Hand-drawn IPM pyramid with layers: Prevention → Monitoring → Cultural/Physical → Biological → Least-toxic sprays last

Microclimate cues (why timing differs)


  • Fog belt (Sunset 17; many coastal 16 pockets): long leaf-wetness → downy mildew & slugs/snails more likely.

  • Thermal belts & inland (Sunset 14–16): warm/dry spells → spider mites, aphids, whiteflies build faster. Dust + heat favors mites.


Diagnostic quick tree (symptom → first move)


  • Sticky leaves + ants + curled tips → aphids → blast with water; control ants (barriers/baits) so natural enemies can work; oils/soaps only if needed.

  • Serpentine leaf tunnels → leafminers → remove mined leaves; protect seedlings with row cover; conserve parasitoids.

  • Shot-hole “pepper” on seedlings → flea beetles → row cover early; keep weeds down; damage is mostly cosmetic past seedling stage.

  • Big chews + green/black frass → hornworms → hand-pick; leave parasitized larvae; Btk for small larvae.

  • Silvery stipple + fine webbing (hot/dry) → spider mites → rinse foliage, reduce dust; encourage predatory mites; oils/soaps if needed.

  • Slimy shreds, missing seedlings (wet) → slugs/snails → remove shelters, night hand-pick, iron-phosphate baits.

  • White powdery patches → powdery mildew → resistant varieties + airflow; fungicides only on susceptible hosts and early.

  • Yellow angular lesions, white down underside (cool, very humid) → downy mildew → keep foliage dry/vented; morning water; increase spacing.


Hand-drawn preventing common garden pest signage, bay area garden nerd

Tactics you’ll actually use (and when)


Cultural/physical (first line)


  • Row cover: put on before pests arrive; remove/vent once plants can tolerate light damage; over-hoops (0.5–0.9 oz cloth).

  • Reflective mulch: silver/aluminum surfaces repel aphids, thrips, whiteflies on young crops and can reduce virus spread; best early in the season.

  • Ant control for honeydew pests: sticky barriers/baits around trunks to stop ant “bodyguards” — critical for aphid/scale/whitefly control.

  • Water/airflow: morning irrigation, mulch to cut splash, and strong airflow reduce downy/powdery mildews.


Biologicals & natural enemies


  • Preserve predators/parasitoids (lady beetles, lacewings, parasitoid wasps, predatory mites) by avoiding broad-spectrum sprays; provide nectar/pollen and control ants.


Least-toxic products (only if needed; follow labels)


  • Insecticidal soaps & horticultural oils: contact materials for soft-bodied pests/mites; require thorough coverage; avoid heat/drought stress periods.

  • Btk (Bacillus thuringiensis kurstaki): caterpillars only; target young larvae.

  • Iron-phosphate baits: for slugs/snails; lower risk when used as directed.


Pest directory — Bay-Area tuned


Aphids


ID: soft-bodied clusters on tips/undersides; honeydew + ants, sooty mold.

Biology: rapid reproduction; many host species.

Monitor: weekly checks of tender growth; watch for ants.

Prevention/Control: blast with water; keep ants off plants (barriers/baits); protect natural enemies; spot-treat with oils/soaps if needed; avoid excess N.


Hand-drawn aphids on shoot tips and undersides; shiny honeydew with ants and slight leaf curl; muted palette highlights key identification cues

Whiteflies


ID: tiny white adults fly when disturbed; immobile nymphs do most damage.

Monitor/Prevention: remove infested leaves, reduce dust; reflective mulch to repel; yellow sticky cards to monitor (and reduce lightly).

Control: oils/soaps can suppress; conserve predators/parasitoids.


Hand-drawn whiteflies lifting from leaf undersides; nymphs on veins, sticky honeydew and faint sooty mold; reflective mulch icon for prevention.

Imported cabbageworm / looper / diamondback moth (brassicas)


ID: white butterflies; green velvety larvae; windowing holes + green frass.

Monitor: scout undersides weekly; look for eggs/frass.

Control: floating row cover early; hand-pick; Btk on small larvae.


Cabbageworm, cabbage looper, diamondback moth larva, on cabbage leaves

Leafminers (beet/chard/spinach, etc.)


ID: winding, whitish mines; small black-gray flies are adults.

Monitor: look for fresh mines; protect seedlings.

Control: remove mined leaves; row cover; conserve parasitoids; usually no sprays in home gardens.


Hand-drawn spinach leaf with serpentine mines and tiny exit holes; magnifier inset; remove mined leaves and protect seedlings with a row cover.

Spider mites


ID: stippling/bronzing; fine webbing in hot, dusty weather.

Monitor/Prevention: reduce dust; rinse foliage; keep plants unstressed.

Control: protect predatory mites; oils/soaps if needed, thorough coverage.


Hand-drawn leaf with silvery stippling and fine webbing; rinse icon and predatory mite silhouette show first IPM steps for hot, dusty conditions.

Hornworms (tomato/pepper)


ID: large caterpillars; look for big green/black droppings; rear horn.

Control: hand-pick (evening); leave wasp-parasitized larvae (white cocoons); Btk for small larvae if needed.


Hand-drawn tomato hornworm on a stem with chewed foliage and frass; a second larva carries white cocoons—parasitized, so leave it for wasps.

Slugs & snails


ID: shredded foliage, slime trails; worst after first rains and in mulchy, shaded areas.

Control: remove shelters, hand-pick at dusk; traps; iron-phosphate baits as needed.


Hand-drawn slug and snail beside a mulched bed; faint slime trail. Dusk hand-pick cue plus trap and iron phosphate bait

Powdery mildew (multiple hosts)


Conditions: cool nights + dry days; doesn’t require leaf wetness.

Control: resistant varieties, airflow; fungicides work best protectively or at first sign — late applications have poor results.


Downy mildew (greens/lettuce/spinach & others)


Conditions: needs free water/high humidity (often after fog/rain); lesions are angular/yellow on top, white down beneath.

Control: water mornings only, vent covers, increase spacing; remove heavily infected leaves.


Hand-drawn panel: floating row cover over seedlings, lady beetle and parasitoid wasp icons nearby, and a “no ants” trunk band

Field rules you can print


  • Scout once a week (2 minutes/bed).

  • Confirm ID before acting; set a threshold (tolerate light damage).

  • Fix causes first (water, airflow, sanitation).

  • Exclude/hand-remove; protect natural enemies; rotate crops.

  • If you must spray, pick the least-toxic option that fits the pest and read the label.



Sources & Further Reading


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