Holes in lettuce

Asked March 10, 2017, 1:21 PM EST

I planted some lettuce in a standup raised bed a week ago. They are doing well, but now one plant has holes in a leaf or two. It's probably a bug, and I'd like a suggestion for an effective but environmentally friendly (and non-carcinogenic!) way to handle this. Thanks.

Clackamas County Oregon raised bed gardening pest issues horticulture

2 Responses

This looks very much like slug damage - irregular holes that look "chewed" on. Slugs like cool wet conditions (Oregon spring!), and tasty tender seedlings - like your lettuce. They are active at night, so it's very likely that you won't see them. They can also be tiny.

Prevention is a good goal. Slugs are most active at night. They like to hide under boards, stones, debris, etc., so removing these can be very helpful. Limiting moisture by targeted watering (hand watering, soaker hoses or drip irrigation), but right now, that's impossible. You can also choose plants that they don't like - but both humans and slugs like lettuce.

There are several methods to control slugs: 1. Hand-picking them; use gloves because of slug slime and put the slugs into soapy water to drown. 2. Traps - after getting rid of hiding places, place boards, overturned pots or even melon rinds. A box made of boards 12"x15" raised 1" off the ground on runners makes a cozy place to hide. You can then find them and dispose of them. 3. Baits - beer in straight-sided containers at ground surface level, or a solution of yeast and sugar water. 4. Barriers - copper interacts with slug slime to create a shock, so copper flashing or foil around your raised bed will discourage slugs for a year or two. You need first to make sure the area is slug-free - with baits or chemical treatment, so you don't trap them where you don't want them. 5. Chemical treatments, bordeaux mix or copper sulfate will repel slugs for about a year, two if you mix it with white latex paint. Metaldehyde is toxic to pets and children, so needs to be used very carefully. Iron sulfate (Sluggo or Escar-Go) is safe for children, pets, birds and fish and is effective.

This article, Snails and Slugs gives you more extensive information.

Thanks so much - you are right, tiny slugs. I thought I would see slime trails if it was slugs, but I guess not if they are tiny or if they hide in the soil. I put a small bowl with beer in overnight (on a rare non-rainy night) and sure enough I caught a tiny slug. I am now using Sluggo for control.

Thanks to you and all involved in providing this very helpful service.
Jonathan More