How to deal with Plum Curculio

The Plum Curculio is a major pest of stone and pome fruits, especially plums, peaches, apples, and cherries in North America.

Spray Schedule

Plum Curculio Spray Schedule Chart (may vary by region)

Stage	Timing	Target	Recommended Products	Notes
Petal Fall	When most petals have dropped	Adult curculios	Conventional: Imidan, Sevin, Asana Organic: Surround WP, Spinosad (Entrust)	First critical spray. Avoid bloom. Bees are no longer active.
1st Cover Spray	7–10 days after petal fall	Egg-laying curculios	Same as above	Reapply sooner if heavy rain occurs.
2nd Cover Spray	7–10 days after 1st cover	Ongoing egg-laying	Same as above	Continue to monitor for new fruit scars or drops.
3rd Cover Spray optional	7–10 days after 2nd cover	Late-season activity	Same as above	Only if needed, especially in high-pressure areas or Southeast US.
Monitoring	Start before petal fall	Adult migration	Traps, limb jarring, fruitlet inspection	Begin scouting when temps reach 60°F.
Clean-Up & Sanitation	Throughout season	Larvae in dropped fruit	Collect and destroy dropped fruit	Reduces next year’s population. Weekly checks recommended.
Off-Season Prep	Late summer/fall	Overwintering adults	Light tilling, orchard sanitation	Disturb soil and remove leaf litter where adults overwinter.

✅ Product Details & PHI (Pre-Harvest Interval)

Product	Type	PHI (Days)	Key Notes
Imidan (phosmet)	Conventional	7–14	Restricted use in some areas
Sevin (carbaryl)	Conventional	3–7	Toxic to bees; use post-bloom only
Asana (esfenvalerate)	Conventional	21	Long PHI; very effective
Surround WP (kaolin clay)	Organic	0	Apply before activity begins; frequent reapplication
Entrust SC (spinosad)	Organic	7	Effective for light infestations

Additional Information

What is Plum Curculio?

The Plum Curculio is a small, snout-nosed beetle (a type of weevil) that damages fruit by feeding and laying eggs inside developing fruit. It is especially problematic in home orchards and organic fruit production, where chemical controls are limited.

Identification

Adult Beetles:

Size: ~4–6 mm (1/5 inch)
Color: Brownish-gray with mottled patterns
Snout: Long and curved (weevil characteristic)
Legs: Have a rough, bumpy texture

Larvae:

Small, legless grubs with white, curved bodies and brown heads
Develop inside the fruit

Life Cycle

Overwintering: Adults overwinter in leaf litter, woodland edges, or hedgerows.
Spring emergence: When temperatures exceed ~60°F (15.5°C), adults emerge and migrate to orchards.
Feeding and egg-laying: Females make crescent-shaped cuts in young fruit and deposit eggs.
Larval development: Larvae hatch and feed inside fruit, causing premature fruit drop.
Pupation: Larvae exit dropped fruit, burrow into soil, and pupate.
New adults emerge: Depending on location, one or two generations may occur per year.

Damage Symptoms

Crescent-shaped scars on fruit skin (egg-laying marks)
Premature fruit drop
Misshapen or pitted fruit
Internal fruit damage with tunneling and frass

Gummosis from Plum Curculio

Gummosis is the oozing of sticky, amber-colored sap from a tree, and when it’s caused by Plum Curculio, it’s a defensive response by the tree to insect injury.

What’s Happening?

When a Plum Curculio female lays eggs, she punctures the fruit skin or twig with her snout, and may also make a crescent-shaped scar to prevent the fruit from healing over the egg.

If the beetle damages young peach or plum fruit, or in some cases young bark, the tree may respond by producing gum (sap) at the site to seal off the injury.

This is what you see as gummosis.

What It Looks Like

Clear to amber sap blobs oozing from:
- Fruit (less common)
- Small twigs or branch crotches near fruit clusters
Sometimes mixed with sawdust-like frass if the injury is deeper
Can harden and turn dark over time

Why It Matters

Gummosis alone won’t kill the tree, but it’s a sign of stress or pest damage
Repeated Plum Curculio attacks can lead to:
- Loss of fruit
- Twig dieback
- Entry points for disease (e.g., Cytospora canker)

Note:

Gummosis can also be caused by borers, mechanical damage, or fungal diseases like Cytospora, so make sure you confirm that the cause is Plum Curculio by checking for:

Egg-laying scars
Early fruit drop with larvae inside
Curculio adults in traps or by shaking branches

When to Monitor:

Early spring through fruit set

How to Monitor:

Use beating trays or shaking limbs over a cloth to dislodge beetles
Monitor temperature (watch for 50–60°F soil/air temps)
Observe for crescent scars on fruitlets
Use traps (e.g., pyramid or limb-jarring traps with attractants)

Control Methods

1. Cultural Controls

Sanitation: Remove and destroy dropped or infested fruit
Prune trees to improve air flow and access for treatments
Tillage: Light soil disturbance in late summer may disrupt pupation

2. Physical Controls

Bagging fruit (labor-intensive but effective)
Sticky traps or bands to catch adults

3. Biological Controls

Natural enemies include:
- Parasitic wasps (Hymenoptera)
- Nematodes for larvae in soil
Encourage predators like birds and beneficial insects

4. Chemical Controls

Timing is critical!
Apply insecticides at:
- Petal fall (just after flowering)
- Follow-up sprays during fruit development (especially after rain)
Common active ingredients:
- Carbaryl
- Esfenvalerate
- Phosmet
- Organic: Spinosad or Kaolin clay (Surround®) as deterrent

⚠️ Always follow local guidelines and label instructions for pesticide use.

Regional Considerations

Northern US & Canada: Usually 1 generation per year
Southeast US: 2–3 generations possible due to longer warm season

Can I save my fruit if infected? NO, but…

If your peaches are already infected with Plum Curculio, don’t worry — while you can’t save the fruit that already has larvae inside, you can still protect the rest of the crop and prevent a worse infestation next season.

Step-by-Step: What to Do After Infection

1. Identify the Damage

Look for:

Crescent-shaped scars on fruit — a sure sign of egg-laying
Premature fruit drop — means larvae are inside
Frass (sawdust-like excrement) or tunnels if you cut open dropped fruit

💡 Fruit with larvae inside cannot be saved. Focus on prevention from this point forward.

2. Remove and Destroy Dropped Fruit

Critical step to break the life cycle
Larvae leave the dropped fruit and burrow into the soil to pupate
Do this every few days until drop stops
Don’t compost this fruit — bag and trash it or burn it (if permitted)

3. Spray Remaining Fruit ASAP

Even if damage has begun, new eggs can still be laid in uninfected fruit.
Apply a cover spray to kill any remaining adult beetles.

Recommended Products (depending on your approach):

Type	Options	Reapply
Conventional	Sevin (carbaryl), Imidan (phosmet), Asana (esfenvalerate)	Every 7–10 days or after rain
Organic	Surround WP (kaolin clay), Spinosad (Entrust SC)	Every 5–7 days or after rain

⚠️ Always follow pre-harvest intervals (PHIs) — for peaches, this can be 7 to 21 days depending on the product.

4. Till or Disturb Soil (Post-Harvest)

After harvest, lightly till the soil under trees to expose pupating larvae to predators or weather. This helps reduce next year’s curculio population.

5. Plan for Next Year

To stop the cycle permanently:

Start sprays at petal fall next spring — don’t wait for damage
Use traps or monitor temperatures to time your first spray
Apply kaolin clay early if growing organically

Quick Recap: After Infection

Task	Why It Matters
Remove dropped fruit	Stops larvae from maturing in soil
Spray remaining fruit	Prevents more eggs from being laid
Till soil in late summer	Disrupts pupation
Prep early for next year	Keeps population from bouncing back