Slugs Are Eating My Ripening Strawberries Overnight

Discovering that ripe strawberries — or fruits on the verge of ripening — have large, ragged holes eaten through them overnight is one of the most dispiriting moments of the strawberry season. Slugs are strongly attracted to ripe and near-ripe strawberry fruits, which combine the sweetness and high water content they need with a position at or near ground level where slugs actively forage at night and in wet weather. During a warm, wet June, slug damage can decimate a strawberry harvest in a matter of nights.

Why strawberries are so vulnerable

The fruits hang close to — or often rest on — the ground, making them easily accessible to slugs that forage at soil level. Ripe fruit is soft and has broken skin (where achenes are) that slugs can enter easily. Dense leaf cover provides the daytime shelter slugs need. The combination makes a strawberry bed in peak fruiting season almost ideal habitat for slugs. The problem is worst in wet years and on beds with poor drainage or with dense leaf mulch that stays moist.

Straw mulch — for the right reasons

The traditional straw mulch placed under strawberry plants is primarily to keep fruits off the soil, which reduces contact between fruit and the moist ground where slugs travel, reduces direct fruit-to-soil disease transmission (botrytis), and keeps the fruit clean. It does not, however, deter slugs — quite the opposite, the straw provides additional shelter for them. The benefit of raising the fruit off the soil still outweighs this, but combine straw mulch with other control measures for the best result.

Practical slug controls during fruiting

Ferric phosphate pellets (wildlife-safe, approved organically) scattered between plants work well when applied fresh before a wet period — the pellets need to be intact to be effective and dissolve in prolonged rain, requiring re-application. Nightly torch inspection and hand-removal of slugs is highly effective during the peak fruiting period (two to three weeks). Harvest ripening fruit every two days rather than waiting for full ripeness — slugs damage the most ripe fruit first, so picking slightly early removes their primary target. A collar of sharp grit or wool pellets around the perimeter of the bed provides some additional deterrence.