Thrips: Identification and Treatment Guide

Thrips are tiny, elusive pests that can cause significant damage to house plants before you even realize they’re present. Their feeding creates distinctive silvery scarring on leaves, and they have a particular fondness for flowers. While challenging to control, thrips can be managed with persistent treatment.

What Are Thrips?

Thrips (the word is both singular and plural) are very small, slender insects in the order Thysanoptera. They’re so small that they’re often difficult to see with the naked eye, but the damage they cause is unmistakable.

Physical Characteristics

Size and Shape:

• Extremely small (1/25 to 1/12 inch long)
• Slender, elongated body
• Narrow, almost thread-like
• Fringe of hairs on wings
• Difficult to see without magnifying glass

Colors:

• Yellowish-tan
• Brown or black
• Some species dark, others pale
• Nymphs often lighter colored
• Adults may appear striped

Life Stages:

• Eggs (inside plant tissue)
• Nymphs (2 stages, wingless)
• Pre-pupae and pupae (often in soil)
• Adults (with fringed wings)

Movement:

• Very fast-moving when disturbed
• Jump or fly short distances
• Can fly (though not strong fliers)
• Tend to hide in flowers and new growth

Feeding Behavior

How They Feed:

• Rasp leaf surface with mouthparts
• Scrape away cells
• Suck out plant juices
• Leave behind silvery scars
• Prefer tender tissue

Preferred Sites:

• Flowers (favorite)
• New growth and buds
• Undersides of young leaves
• Protected areas

Identification

Visual Signs

The Damage (Easier to See Than the Pest):

Silvery Streaks or Scars:

• Most distinctive symptom
• Silvery, papery appearance
• Scars on leaf surface
• Where thrips scraped cells away
• Permanent damage (doesn’t heal)

Stippling:

• Tiny pale dots
• Where individual feeding occurred
• May appear silvery or bronze
• Similar to spider mite damage but different pattern

Leaf Distortion:

• New leaves curled or twisted
• Stunted growth
• Deformed appearance
• Buds fail to open properly

Black Dots:

• Thrips excrement (frass)
• Tiny black specks on leaves
• Visible with magnifying glass
• On upper and lower leaf surfaces

Flower Damage:

• Streaking on petals
• Brown edges on petals
• Deformed flowers
• Flowers fail to open
• Petals with papery appearance

General Symptoms:

• Leaves with silvery sheen
• Bronze or grayish discoloration
• Distorted new growth
• Overall weakened appearance

The Insects Themselves

How to See Them:

Shake Test:

• Hold white paper under flower or leaf
• Tap plant sharply
• Thrips fall onto paper
• Look for tiny, moving specks
• Use magnifying glass

Direct Observation:

• Look in flowers with magnifying glass
• Check undersides of new leaves
• Fast-moving when disturbed
• May jump or fly

Appearance:

• Very small, slender
• May appear as tiny dark lines
• Wings look fringed under magnification
• Move quickly

Where to Find Them

Flowers:

• Inside flower petals
• Deep in blooms
• Favorite hiding spot
• Check all flowers carefully

New Growth:

• Unfurling leaves
• Tender shoot tips
• Buds
• Soft tissue preferred

Leaf Undersides:

• Young leaves primarily
• Near veins
• Protected areas

Why They’re on Your Plants

How Thrips Arrive

Flowers and Plants from Florist/Nursery:

• Very common source
• Hidden in flowers
• May not see them initially
• Spread to house plants

Flying Indoors:

• Adults can fly
• Enter through windows
• Attracted to flowers and light
• Drawn indoors from outside

Plants Summered Outdoors:

• Pick up thrips outside
• Bring in unknowingly
• Common in late summer/fall

Bouquets and Cut Flowers:

• Thrips in commercial flowers
• Spread to nearby plants
• Very common problem

Conditions That Favor Thrips

Environmental:

• Warm temperatures (70-85°F)
• Dry conditions
• Low humidity
• Typical indoor conditions ideal

Plant Factors:

• Flowering plants (highly attractive)
• Tender new growth
• Stressed plants
• Indoor year-round conditions

Treatment

Why Thrips Are Challenging

Difficulties:

• Very small (hard to see)
• Hide in flowers and tight spaces
• Life stages in different locations (some in soil)
• Can fly (spread easily)
• Eggs inside plant tissue (protected)
• Multiple generations overlap

Advantages:

• Damage is visible (know they’re there)
• Adults easier to kill than some pests
• Can be controlled with persistence

Immediate Actions

1. Isolate the Plant

• Move immediately
• Check all nearby plants (especially flowering)
• Keep isolated during treatment
• Thrips spread easily

2. Remove Flowers

• All flowers and buds
• Even if they look healthy
• Thrips hide deep in flowers
• Critical step
• Dispose in sealed bag

3. Remove Damaged Leaves

• Heavily scarred leaves won’t recover
• Reduces thrips population
• Improves plant appearance
• Bag and dispose

4. Set Up Sticky Traps

• Blue or yellow sticky traps
• Catches flying adults
• Monitors population
• Place near plant

Treatment Methods

Method 1: Insecticidal Soap

Effectiveness:

• Good for thrips
• Kills on contact
• Safe for most plants

How to Use:

1. Mix according to package directions
2. Spray entire plant thoroughly
3. Focus on undersides and new growth
4. Spray into any remaining flowers
5. Ensure complete coverage
6. Repeat every 5-7 days
7. Continue for 3-4 weeks

Pros:

• Relatively safe
• Effective on adults and nymphs
• Inexpensive

Cons:

• Must contact thrips
• Doesn’t kill eggs
• Requires repeated application

Method 2: Neem Oil

How It Works:

• Contact kill
• Anti-feedant (thrips avoid treated plants)
• Disrupts lifecycle

Application:

1. Dilute according to package directions
2. Add few drops dish soap
3. Spray all plant surfaces
4. Apply in evening
5. Repeat every 7 days
6. For 3-4 weeks minimum

Pros:

• Organic
• Multiple modes of action
• Also deters feeding

Cons:

• Can smell
• May burn in heat/sun
• Slower than some options

Method 3: Spinosad (Very Effective)

What It Is:

• Derived from soil bacteria
• Organic insecticide
• Highly effective on thrips

How to Use:

1. Follow package directions
2. Spray thoroughly
3. Covers all surfaces
4. Repeat every 7-10 days
5. Very effective after 2-3 applications

Pros:

• Very effective on thrips
• Organic
• Relatively safe
• Fast-acting

Cons:

• Can harm beneficial insects
• More expensive
• Must follow label carefully

Method 4: Systemic Insecticide

When to Use:

• Severe infestations
• Other methods failing
• Valuable plants
• Recurring problems

How It Works:

• Applied to soil
• Absorbed by plant
• Thrips ingest when feeding
• Long-lasting protection

Application:

1. Follow package directions exactly
2. Apply to moist soil
3. Water in thoroughly
4. Takes 1-2 weeks to work
5. Protects for weeks

Common Ingredients:

• Imidacloprid
• Acephate

Pros:

• Very effective
• Long-lasting
• Treats whole plant

Cons:

• Chemical
• Can’t use on edibles
• Time to take effect
• Safety precautions needed

Method 5: Shower/Spray

Physical Removal:

• Take to shower or use hose
• Strong spray of water
• Dislodges thrips
• Non-toxic

How to Do It:

1. Spray all surfaces thoroughly
2. Focus on undersides
3. Use strong but not damaging pressure
4. Repeat weekly during treatment

Effectiveness:

• Reduces population
• Good supplement to chemical treatment
• Doesn’t kill but removes

Method 6: Sticky Traps

Purpose:

• Catches flying adults
• Monitors population
• Helps but not complete solution

Types:

• Blue traps (most attractive to thrips)
• Yellow traps (also work)

Placement:

• Just above plant
• Near affected plants
• Check and replace regularly

Pros:

• Non-toxic
• Early warning system
• Reduces flying adults

Cons:

• Doesn’t catch all life stages
• Not sufficient alone
• Must combine with other methods

Comprehensive Treatment Plan

Week 1:

• Remove all flowers and heavily damaged leaves
• Spray with insecticidal soap or spinosad
• Set up sticky traps
• Shower plant

Week 2:

• Second spray treatment
• Monitor sticky traps
• Continue inspections

Week 3:

• Third treatment
• Shower plant again
• Check for remaining thrips

Week 4:

• Final treatment
• Continue monitoring
• Should see significant improvement

Ongoing:

• Keep sticky traps up
• Monitor for 4-6 weeks
• Quick action if thrips return

Combination Approach (Best Results)

1. Remove all flowers
2. Apply systemic insecticide to soil
3. Spray with spinosad or insecticidal soap weekly
4. Use blue sticky traps
5. Shower plant weekly
6. Continue for full 4 weeks minimum

Prevention

Inspection and Quarantine

New Plants:

• Inspect flowers very carefully
• Check new growth
• Quarantine 2-3 weeks
• Monitor with sticky traps during quarantine

Cut Flowers:

• Inspect bouquets before bringing inside
• Keep cut flowers away from house plants
• Common thrips source

Plants from Outdoors:

• Inspect thoroughly before bringing in
• Check all flowers and new growth
• Consider preventive treatment
• Quarantine

Cultural Practices

Remove Fading Flowers Promptly:

• Don’t let flowers remain on plant
• Deadhead regularly
• Reduces thrips habitat

Avoid Outdoor Plants During Peak Season:

• Summer = peak thrips
• Bring inside before heavy thrips pressure
• Or treat before bringing in

Sticky Traps as Early Warning:

• Keep near flowering plants
• Check weekly
• Catch before heavy infestation

Maintain Plant Health:

• Proper care makes plants resilient
• Can tolerate some damage better
• Recover more quickly

Most Susceptible Plants

Highly Attractive:

• Orchids
• African violets
• Roses
• Hibiscus
• Cyclamen
• Gloxinia
• Most flowering plants

Also Affected:

• Ficus
• Citrus
• Many vegetables (if growing)
• Plants with soft new growth

When to Be Concerned

Cosmetic Damage:

• Thrips damage permanent
• Scarred leaves won’t heal
• New growth should be clean after treatment
• Mostly aesthetic issue

Severe Infestations:

• Heavy scarring
• Significant flower damage
• New growth severely distorted
• Plant weakened
• Can impact plant health

Common Mistakes

Not Removing Flowers:

• Leaving flowers on plant
• Thrips hide and breed in flowers
• Treatment won’t work with flowers present
• Must remove ALL flowers

Stopping Treatment Too Soon:

• Appears gone but eggs still hatching
• Must treat for full 3-4 weeks
• Different life stages

Only Treating Visible Areas:

• Missing undersides
• Not treating thoroughly
• Thrips hide in tight spaces

Not Using Sticky Traps:

• Miss adult population
• No way to monitor effectiveness
• Traps important tool

Success Indicators

You’re Winning When:

• No new silvery damage on new growth
• Few or no thrips on sticky traps
• New leaves emerging clean
• Flowers (if any) undamaged

Continue Treatment:

• Until no thrips on traps for 2 weeks
• New growth clean for 3-4 weeks
• Then monitor monthly

Bottom Line

Thrips are challenging but controllable:

Quick Action Plan:

1. Isolate plant immediately
2. Remove ALL flowers and buds
3. Remove heavily damaged leaves
4. Set up blue sticky traps
5. Spray with spinosad or insecticidal soap
6. Repeat weekly for 4 weeks
7. Monitor sticky traps

Prevention:

• Inspect flowers carefully before purchase
• Quarantine new plants
• Use sticky traps as early warning
• Remove fading flowers promptly
• Keep cut flowers away from plants

Best Treatments:

• Spinosad (most effective spray)
• Systemic insecticide (for severe cases)
• Blue sticky traps (monitoring and catching adults)
• Remove flowers (critical step)

With persistent treatment focusing on all life stages and using multiple methods, thrips can be eliminated!