Worms eating seeds

General Discussion
1

I’m stratifying in peat this year.

My potted Pretty Polly Pink pollinations weren’t ripe when winter hit so I pulled the pots inside for a month or so to let the seeds ripen.

David has mentioned that polyantha seed germinates better at a straight 50 degrees F rather than being given a conventional cold stratification period. Therefore I kept these seeds on a cool windowsill.

When I pulled them out to check for early germinations a while ago I could find NO seeds in the bags. Anything that looked like a seed put up no more resistance to rubbing my fingers together than a rice hull. I spotted some tiny white worms.

Today I double checked and still can’t find any seeds and saw the white worms in the picture. They’re moving slowly.

So maybe this is why I haven’t had luck germinating Darrow’s Enigma and other polys. I actually did spray some imidacloprid and trebucolan on these in the summer, but obviously not enough. In the future I’m going to douse the hips with imidacloprid and soak the seeds in it before stratifying.

It would be interesting if anyone knew what these worms are and if they only hit polyantha seeds. I remember Margit mentioning something about a wasp larvae? They’re definitely different than the bigger grub-like worms that resemble achenes and freak you out when your seed starts writhing.

See picture:
EABEDA1B-71E1-4CFF-969B-19D1CEFB1393.jpeg

2

UPDATE:

I’m checking on my other seeds and am seeing quite a few of the same worms here and there. These larger (non-poly) seeds appear to be unharmed.

So maybe I was jumping to conclusions. My peat is not sterilized. The worms could just be in the peat and unrelated to the rose seeds.

The poly seeds could have rotted from other reasons.

Any entomologists out there want to try to identify these buggers?

3

Fungus gnat larvae? https://www.google.com/search?q=fungus+gnat+larvae&client=firefox-b-1-d&sxsrf=ACYBGNRMGFMGEDgCzreEQrv90AKdBapEMg:1579816409359&tbm=isch&source=iu&ictx=1&fir=XIV3cUrI48SD-M%253A%252C3G3AALnxgs4mUM%252C_&vet=1&usg=AI4_-kSjBr6_N3iECI_SaHObYMNMkbrXNQ&sa=X&ved=2ahUKEwjHj4_f2prnAhWFu54KHZshCPwQ9QEwAHoECAcQAw#imgrc=XIV3cUrI48SD-M:

4

They seem to be soil nematodes. They are predominantly predators and feed on fungi, microorganisms and protists. They won’t eat seeds. Maybe your incubation conditions favored some fungi production, that, in turn, led to multiplication of nematodes. Just a thought.

5

Pretty sure fungus gnat larve.

I usually find the extremely tiny white worms on the “failed to take” cuttings u/g cane that have blackened and rotted from too damp an environment. Then usually 3- 4 weeks after planting (wetting) cover trays plagued with black fungus nat flies. These disappear after 4-6 weeks, hopefully helped on their way by carnivorous mites that are seeded in to get the worms then come spider mites on the taken. Been going on for decades … occasionally resort to fly tape and insecticide human friendly sprays - by then its May out the cuttings go into the real world - the bug problems disappear for me.

… l found supposedly sterilized soil never interrupted this cycle.

6

In your baggies? That’s odd.

I generally think of fungus gnat larvae (of which I’ve had more than my share) as being slightly more translucent and a bit less, I’ma say, lanceolate(?) on the end. I might lean towards nematodes, but I’m not overly familiar with such. Regardless, I don’t know that it would be fair to call them out as the culprits.

I see such on my failed cuttings way too often, but have never seen such on seeds. (Most of my cuttings fail, alas…) My assumption has been that they are detritivores feeding on decaying matter.

I have recently been sterilizing seeds with a dilute peracetic acid* wash which seems to cut down on the amount of fungus without creating a noticeable effect on germinations, BUT I would want to do a controlled study before making that assertion too boldly. I also sterilize my media – a step, the merits of which I sometimes question. (I steam sterilize moist media in the microwave, but my medium is predominantly peat. I use the peat as it ostensibly has enzymes that inhibit fungal growth, but wonder if the heat of sterilization wouldn’t destroy those enzymes. I wonder if there are studies on such out there… Anybody know?? I’m not sure if my wife has determined the cause of the periodic, strange, musky smell around the microwave, but I digress…)

At any rate, stratifying in small zip lock bags**, I might get some fungi (which are seemingly relatively inconsequential to healthy seeds) but I’ve never seen any fauna of the genre you have… I would guess yours were in your medium.

And while I’m inclined to think the seeds might have become worm fodder because they failed, and not vice versa, I will note that some hungry detritivores are known to resort to attacking things that are perhaps not so dead when their preferred food source is scarce…

( * You can look up peracetic acid (CH3COOH) which is a sanitizer made from combining hydrogen peroxide and acetic acid (vinegar): H2O2 + CH3COOH <–> CH3OOOH + H2O. I mix about 2-3 parts hydrogen peroxide (3%) with one part vinegar (5% – I use cider) – a solution which leans towards the peroxide. I probably dilute this solution with a good five to ten parts water to one part solution – I’m not very scientific about it. I’m not saying the use of such has merit – I have never done a real test to determine/compare any benefits /detriments in doing this – I’m just saying it’s my current procedure.)
( ** The bags I use are left-over pill-crusher bags, and hence pretty heavy duty little guys, but ULine makes PP bags that should certainly seal well enough to prevent bugs from getting in.)
Finally, Don’t do what I do. I am not proposing any of the above as good ideas. :wink:

7

They seem to be soil nematodes.

Yes, I agree with Giessen. I used to raise nematodes to feed small fish fry, and also used to let my students look at nematodes under magnification as part of my science classes. The terrestrial nematodes in the aquarium hobby are frequently called “microworms”, although in reality that probably covers a number of actual species. The terrestrial nematodes in the aquarium hobby look quite similar to the critters in Jbergeson’s picture.

(As an aside there are also aquatic nematodes, one type of which are called “vinegar worms” or more confusingly “vinegar eels” and live in dilute vinegar–I think that may be one of the reasons that vinegar manufacturers filter and/or pasteurize vinegar prior to bottling, although it may be less of an issue with modern sanitary food production. I think it was historically an issue in vinegar production, though. Students think they’re really neat under magnification!)

I’ll admit to not being a gnat larvae expert :), but under magnification wouldn’t gnat larvae tend to have a recognizable “head” portion…similar to other insect larvae such as terrestrial fly larvae or to the aquatic midge larvae or crane fly larvae that I’ve collected? In the links that Kim sent, you can get a sense for this “head” portion on many of the internet pictures of gnat larvae. I don’t see a head portion in Jbergeson’s picture, although the resolution does get a little difficult when I zoom way in, so I could be wrong. Of course I do recognize that nematodes have a “front” end (where the food goes in!) as well, but it’s not really visually recognizable like the head section of insect larvae.

Anyhow, based upon my person experience with nematodes as opposed to insect larvae (although not with gnat larvae specifically), they sure look like nematodes to me.

Regards,
Matt

8

my medium is predominantly peat. I use the peat as it ostensibly has enzymes that inhibit fungal growth, but wonder if the heat of sterilization wouldn’t destroy those enzymes.

Philip, that’s interesting. I’ve never used peat with rose seeds–I’ve mostly used vermiculite to stratify rose seeds and other small seeds. But maybe I’ll try peat out.

Although I’ve not tried it with rose seeds, I have used damp peat extensively with larger tree seeds, especially chestnut seeds. Peat is a popular option for stratifying them because, as you noted, it is thought to inhibit fungal growth. Chestnuts must be kept damp, but also are quite susceptible to fungus. I believe, by the way, that the reason that peat discourages fungal growth has to do with its inherent low pH (being naturally acidic). As you suggested, heat does destroy/deactivate some enzymes. But if I’m correct and the anti-fungal properties are actually due to low pH, then the heat-sterilization that you’re doing would have little to no impact (I think) upon peat’s acidic nature. So peat should work fine after having been heated.

Incidentally, if you’re ever looking for an alternative to heating peat in the microwave…I personally bag peat up in a black trash bag, add the amount of water that I want, and leave it out on a summer or early fall day in the hot sun, preferably off the ground. It gets powerfully hot inside the black bag, which also seems to encourage the peat to absorb the water. I’m not sure what temperature it gets to, but since I’m taking dry peat out of the bale, putting it in a new trash bag, and then heating it to who-knows-what-temperature, it certainly has worked for me. And it keeps my darling wife happy…she might be somewhat skeptical of peat in the microwave :).

Regards,
Matt

9

Oops l forgot to ask the obvious question … any small flies show up yet?

10

I forwarded Joe’s photo to our nematode specialist in Plant Pathology. He says they are too large to be plant/soil nematodes. Gnat larvae is the most likely guess though he mentions a family I never heard of or even now how to say ( enchytraeidae) as a possibility. There are larger nematodes but they are animal pathogens. I’m believing him because we are working on a paper about nematodes on a biofuel plant called miscanthus and he’s ID’d dozens of genera/species in half a dozen groups in soil around that plant and on its roots.

11

I just looked up the enchytraiedae and find that they are called potworms. They are like miniature earthworms. They eat decomposing plant material in pots in greenhouses among other places. Maybe also California pot too.

12

Wasp larvae are segmented looking like the bellows on an accordion. These guys are smooth.

13

Larry, I stand corrected and agree with your colleague regarding the size of common free-living nematodes. The free-living nematodes that I’ve seen are considerably smaller than the creatures in Jbergeson’s picture…I should have thought of size, not just appearance. Oops!..somewhat embarrassing oversight.

If Jbergeson’s peat medium ever came into contact with anything where they might live, then your colleague’s suggestion of Enchytraeidae makes a great deal of sense. To find images of Enchytraeidae that look about the right size for Jbergeson’s picture, one can do an internet search for a type of Enchytraeidae that are commonly called “Grindal worms.” Incidentally, people who purposefully raise Enchytraeidae sometimes raise them on peat.

14

Wow, thanks everyone for the replies!

I can’t find my darn pocket microscope, the use of which seems like a logical next step. Maybe I can capture a photo through it that will help us learn more. But the scope is likely buried under one of my piles of miscellaneous crap…the question is which pile?

Joe

15

I found the microscope. It was fascinating to look at the worms under the scope. Very smooth, with no sign of segmenting or the black head of fungus gnat larvae. Look very much like the Enchytraeus buchholzi mentioned above. Most nematode photos seem more microscopic.

I wish I could have taken a pic but couldn’t hold the scope steady with one hand, plus the worms were on the move.

16

BTW, Joe, the wasp you mentioned is probably the Rose Seed Chalcid. It’s very tiny, and the larvae are tiny fat grub-like things. I collected rugosa hips in Maine years ago, and saw ity-bitty pinholes in a bunch of seeds when I finally got around to processing several years later. Discarded the obviously eaten seeds, and had a remarkably decent germination rate from the remainder. Genus Megastigmus - BugGuide.Net

17

Call me a wimp if you must, but this entire thread gave me the heebie-jeebies. :flushed:

1 Like