Strawberry sap beetle

About

A tiny, oval brown beetle, an eighth of an inch or less, with knobbed antennae and a faint lighter X-shaped mark across its back. It is drawn to ripe and overripe fruit.

Spotting it

Damage

Adults and larvae chew small, deep holes in ripe berries, usually on the side touching the ground. They can bring in fruit rot, and larvae turn up inside picked fruit.

How to find it early

Look for small beetles in holes on ripe berries, especially under leaves at soil level. Bait traps with fermenting fruit or bread dough along wooded edges show when they move in (UMD).

When

Late spring through summer.

Life cycle

Adults spend winter in wooded areas and in blueberry and raspberry patches and move into strawberries as fruit ripens in May and June. A generation takes about 20 days at 69°F, and numbers build through summer.

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Pick often and remove damaged fruit Prevent

   Harvest frequently and completely, and remove overripe, damaged and rotting fruit right away. Destroy it by freezing or by sealing it in a clear plastic bag in the sun. Beds next to woods have more beetles.

2. Bait buckets outside the bed Trap

   Set containers a few feet outside the garden baited with bread dough, overripe fruit, stale beer, molasses-yeast mix or vinegar, and empty and rebait every 3 to 4 days (UMN).

3. Insecticides work poorly Conventional spray

   UMN does not recommend sprays: beetles hide inside and under fruit, and products cannot be used on ripe fruit close to harvest. Sanitation does more.

   If you do spray, use only a product labeled for strawberries, follow its pre-harvest interval, and avoid blooming plants; bifenthrin and carbaryl are highly toxic to bees (PNW 591).

Plants it goes after

Blueberry, Cantaloupe (muskmelon), Cherry (sweet and tart), Peach, Raspberry, Strawberry

Pressure by region

Sourced for Maryland (UMD) and Minnesota (UMN). Other regions are rated low for lack of a source; those ratings are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.