Rootfly - help! Please!

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JohnB
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Hi Folks, Although a gardener for many years, on and off as time, space has permitted, I have recently become an allotment tenant. I have found a problem on my plot and wondered if anyone can suggest a remedy - I'll try to uppload a pic of the problem in a minute. The first time I noticed was a crop of cabbage where some of the cabbages (not all) turned blue and then keeled over. Cabbage rootfly, I thought. Ah well. Next time I'll dunk 'em in Jeyes Fluid before planting - a remedy my grandfather used to use. It worked. However, I then tried growing summer radish, out of a row of radish I got got about 3 to eat while the remaining 200-ish were dumped because they were completely eaten away. Ha! thought I, I'll try winter radish this year. I have China Rose, Blue Moon, Daikon and Black Spanish Round, all doing moderately well, but many of these have been hit by rootfly. I can deal with the rootfly on brassica plants using Jeyes, but can't do anything about direct sown seeds. This really is more than just annoying, it is dreadful because I can't grow any form of brassica without it being completely destroyed by these larvae. I'll now try for an image ... is there any kind of remedy/soil treatment? mesh covers won't work, the eggs seem to be soil-bound, perhaps even over-wintered. I can stop the flying insects, but one crop of radish were covered and still got attacked! To give an idea, 50% of any brassica crop is destroyed by this pest.

Daikon winter radish destroyed by rootfly.
Daikon winter radish destroyed by rootfly.
cabbage-root-fly.jpg (198.71 KiB) Viewed 5151 times
Monika
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John, the actual cabbage root fly lays her eggs in the soil against the plant stem, so do you not use brassica collars round the stem, either bought or home made?
I have never heard of them attacking radishes and the collars wouldn't work there, of course. If the eggs overwinter, as you surmised, turning the soil over several times during the winter might expose them to the the elements or birds.
robo
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If you are going to turn your soil over a few times why not jeyes fluid it each time or go over it with a gas blow torch
Monika
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The other thing you could try is Nemasys nematodes and now would be a good time to apply these.
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Primrose
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Yes, seems a bit drastic but I was wondering whether a diluted watering of Jeyes Fluid Into the drill before sowing would solve the problem

Guess the little creatures are more active in warmer weather but could you treat the whole growing area with a Jeyes Fluidl solution ate autumn/early winter when it's free of plants? A thorough digging as Monika suggests may also disturb them.

Jeyes no longer contains coal tar, hasn't for years, so probably not as efficacious as it used to be.
JohnB
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Joined: Wed May 26, 2021 7:18 pm
Location: Deepest, darkest, Lincolnshire

Hi Folks,
Thanks for the input - I love the idea of BLASTING them with a gas blow torch! Yeaaaahhh! and I'm going to give that a go. I've done a bit more hunting on this and there is a similar fly, same family actually, just a different species called "Turnip Root Fly" which tends to attack radish, turnip and swede. If I could catch a little blighter I'd bung it under a microscope. I think your idea, Monika of nemasys sounds like a cracking idea in the longer term and one to try. I have looked at this and need to find a specific one, I understand they can be a bit specific to a single species of pest, like some slug species, but not all, some root fly species, but not all and so on. Ah well, I'm sure I'll get it sorted one way and get back to you all and let you know what has happened.
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