What might be eating my seedlings (no sign of slugs or millipedes)?

Question

I've got a little greenhouse to get seedlings started and to protect potted vegetables until a bigger, albeit temporary hoop greenhouse can be built (happening now...).

Last night I lost a dozen seedlings...the green, seed leaves were eaten. I spent hours looking at the bottom of the flats, pots...nothing. Only the seedlings on top of my potting bench were accosted so far...weird.

I am in a hostile place for gardens...have been here for only 6 months but see that a greenhouse is the ONLY way to grow anything. I am in the same zone as most of Alaska!

My first thought was slugs...baby ones, yet no sign. No slime trails...cleaned up debris under and around my seedling flats and put in bucket with water to see if anything crawls out. So looked up the millipedes, no sign, and now I think maybe tiny 'army worms'?

I live in Central Oregon. Freezing every night getting up to 70 degrees or more in the daytime. Also, finding lots of tiny chunks of recently eaten seedling leaves in the debris. Confusing. I am very high in the gardening professional arena...but this is new, this place is new and I want to find the culprit before I decide how to deal with this. Bought expensive, non-gmo seed and get attached to my 'babies'. Any ideas?

Answer 1

I am having the same issue in my greenhouse. I believe in our case it is rodents. They are digging holes in the seed flats as well and taking off with larger seeds. They even dig up freshly germinated seeds to nip off and carry away the seed cotyledons! We found a cache of seeds and seed husks inside a folded up chair earlier, so we know it's not all slugs or insect predators. They are not field mice, because the typical mouse traps do not attract them, but the way the debris is being "stashed" leads me to believe they are rodents, all the same. We are new to western Washington, so we haven't been able to pinpoint exactly what kind of rodent they ARE though...

By the way, the only way we've found to prevent the damage is to cover seed flats until the plants are old enough to no longer be attractive. We use inverted, perforated seed trays, but agro-bond fabric tucked all the way around the flat may also work.

Answer 2

This is very curious - you say you found lots of 'recently eaten seedling leaves in the debris'. It strikes me that if something had actually eaten and digested the seedling leaves, anything processed through a creature's digestive system won't be recognisable as a bit of a seedling leaf when it comes out of the other end and is deposited. That sort of implies that something is nipping the leaves off but not actually eating them... Also, what was the debris that you cleared away, exactly? Is there any more debris lurking in the area? If so, all should be swept and cleaned away. The trouble with a greenhouse is, there are all kinds of creatures which will like that environment that may not survive outside, so the range of possible pests is much larger.

In the meantime, it might be worth hanging fly papers or sticky traps from the roof to see if any flying insect gets trapped on them. Also follow Roach's suggestion of going in there with a torch after dark to see if there's anything going on...

Answer 3

I have a similar problem. I've identified the issue as cutworms for me. Food grade diatomaceous earth sprinkled in a small circle around each plant seemed to have done the trick after three or four days.

Slugs are still also a possibility; even if you don't see trails, that doesn't mean they aren't there. You can use a beer trap or place an hollowed half of an orange/grapefruit upside down close by. Turn the peel over in the morning and see what sort of local night dwellers moved in. Might find slugs (or pillbugs too, as others have mentioned).

Answer 4

It might help to take a look at your plants at night with a flashlight, because it sounds like it could be pill bugs and these are often more active at night.