1/4 inch & white, living in coffee grounds & worm compost sounds like potworms. Google potworm image to see. If I remember correctly, putting a slice of milk-soaked bread will attract them & then you can discard the bread. I don't think they're harmful to the plants, though.

Hi Grace My answer may not help you at all but... I live in Sf and have grown dahlias out in the sunset for years (which is one of the worst environments for growing flowers) and in my opinion, you are causing more work than you need to for yourself. I NEVER have started my dahlias indoors, I never have dug them up for overwintering and I rarely even touch them after they bloom in year one. And I (just being honest) have a yard that is the envy of my friends and neighbors. Even in heavier rain years, I never worry about my tubers and in years like this, I find I have to go out and water in the winter in order for them to get ANY moisture. Do I lose dahlias? Sure do. But not often and usually only when I am lazy and allow the snails to have at em when they start sprouting. But if I lose a few (out of 90+ and counting), it gives me an excuse to buy more tubers the next year! You may well grow beautiful dahlias with all the dedication you are showing but for my money, it is much ado about nothing. Dahlias are hardy and once they get used to their environments, they last forever. And you know well in the sunset we get up to 2-3 months of NO SUN and heavy fog. So if I can grow beauties with little maintenance, I am sure you can also. If you prefer the high maintenance route, go for it. But I think you will find it a full time job because there will ALWAYS be something - mold, rot, lack of water, too much water, snails, too much heat (sun), not enough heat, freezing temps, long foggy months, staking, and maybe , just maybe, the tuber was no good from the get go DESPITE what you do! Good luck. And if you live in the sunset and want to see my yard some time, I have dahlias from May to November but the best month is August. Come on by!

Been a while since I have been able to get back here. So Sorry!! I am down loading that PFD as I am here to see if what we are talking about, could be the same thing. I don't know where they came from but it killed an enormous amount of tubers most of them before they could come up (discusted!!) I have treated the whole yard with Ortho MAX...I hate using pesticides since I have pets. I know I put in this Flower bed about March and it had all new purchased dirt in it, so I thought they might have come from either the tubers (dahlias &/or Hostas) or maybe even the new purchased dirt. ( An unwanted bonus...Yikes!! ) Then in the flower bed that has been established for some years prior to purchasing the house I put in Cyclamen about February, and they were doing wonderful I mean really great, set seed and everything, then 3 of the 4 went what I thought was dormant...so 2 weeks ago I decided to plant other bulbs in there place, as soon as I dig them up they were sitting in these little creepy bugs, the tubers/bulbs were not damaged just the leaves, I washed them off gave them a good inspection sprayed them with a fungiside and replanted the little ones with a good dose of Ortho Max, The leaves are once again starting to come back up slowly but surely. This is why we decided to treat the entire yard...I put in a new flowerbed this weekend with Glads and young strawberry plants, I treated the bed before I put the mulch in, I have never had to put anything other than a bit of dish detergent on my Strawberries but I hope to ward off any creepy crawly root chewing scavengers before flowering season starts, once fowering season starts for my strawberries I won't use any pestisides in that flowerbed ( they better not like dish detergent ) It was a bit amusing though when I showed my husband a handful of dirt with the pesty creepy pests in it, all he said is he would be back in a bit, when he returned and he said with 2-20 pound bags of Ortho Max we will just treat the whole yard, those things are GROSS...Just to give you an idea of the over kill, I live in a Mobile home park my entire lot is 40X70!! He has since calmed down he said he would treat the yard that day ( he did )and then in another 10 days then we would do some digging in a few places to determine if we need to continue treatment or change treatments, but just to let you know my cheep Dahlia tubers that I purchased to replace the exspensive tubers, I planted last week are in fact coming up already and don't seem to be bothered by the Ortho Max or the bugs...the expensive tubers that did survive are not doing well even to this day and are always having to be treated with a fungiside, they weren't a good quality when I recieved them so I shouldn't be surprised. I hope you are doing well in the garden with your Dahlias, for me I am keeping my fingers crossed. Thanks for the information... I'll be back

I stumbled upon a solution to this problem (root maggots or something eating my pea seeds). The first batch of peas I planted last spring got mostly eaten before sprouts appeared above the surface. I replanted and then threw a few extra seeds into another part of the garden that was covered in wood-based compost (which had been used as a mulch over the preceding winter). The ones in the wood compost sprouted and the others mostly got eaten by small white worms (root maggots?) Anyways, then I planted a third time. This time I put about a one-half inch layer of wood-based compost on top of the soil, placed the pea seeds on top, and covered with another half inch of the same compost. Just to test the idea, I also planted some more pea seeds directly in the soil as before. The ones in the wood compost germinated at a very high rate, whereas the others all got eaten again. Even though wood compost is probably not the best for vegetable gardening, the peas were able to extend healthy roots down into the soil and produce a good crop of peas. My wood-based compost is from our local landfill, which collects yard debris, composts it, and then sells it. It is mostly derived from evergreen trees and brush (pine and juniper trees and needles.) It is similar in consistency to bark mulch that has rotted for a year or two in the garden. Note I also cover my pea beds with mesh to keep the birds away from my germinating peas, and have found this to be very important. Once the green shoots are above the ground, the birds lose interest, but they love the sprouts and can find them before my feeble human eyes (or nose) can.