Topic: Wireworm and Sowing Mustard

[Chantenay]

I was on my way to buy some mustard seeds to sow where I will be planting potatoes next year, as I have had wireworm in spuds (because the ground is newly cultivated) and I heard they hate mustard.
BUT... I checked in the Organic Catalogue and it says: "wireworms are fond of decomposing mustard plants and eat enough to reach adulthood in a single season, then fly away to find grassland in which to lay their eggs".
Oh dear.  Can someone please de-mystify this for me please?

[Hugh_Jones]

The statement made in your organic catalogue is in fact a suggestion made by the founder of HDRA. It has never been scientifically tested, and in fact runs completely counter to insect physiology: insects are cold blooded and rate of development is strictly related to temperature.  Food quality and quantity may affect eventual size, but not the rate of growth.

In support of the theory that sowing mustard controls wireworm:
1. de Bairacli Levy (1966 - Herbal Handbook for Everyone)
2. G. Franck (1983 - Companion Planting)


3. L. D. Hills (1971 - Grow Your Own Fruit and Vegetables)
4. Lichtenstein, Morgan & Mueller (1964 - Naturally Occurring Insecticides in Cruciferous crops (Journal of Agriculture))
5. Parker & Howard  - (2001 - paper on The Biology and Management of Wireworms - ADAS,Woodthorne)
6. J. Soper (1966 - Biodynamic Gardening)

Finally, see the ADAS paper (2001) Wireworm control using Fodder Rape and Mustard by Frost, Clarke & McLean, on field trials of (inter alia) mustard in Pwllpeiran, which indicated quite reduced levels of damage to potatoes from both wireworm and slugs on plots where mustard was sown and rotovated in after a mere 6 weeks, immediately before potato planting, compared with untreated plots.

[john_miller]

If you want to try to 'multi task' your patch you may get similar results by sowing broad beans overwinter. Some control was measured and described in 1944 in the Annals of Applied Biology. You will increase nitrogen levels, due to their being a legume, hopefully get an edible crop and possibly reduce wireworm larvae simultaeneously.
Hugh's reference can be found at:
http://216.239.41.104/search?q=cache:9ahmN8CoOTgJ:www.organic.aber.ac.uk/library/wireworm%2520control%2520and%2520brassica%2520green%2520manures.pdf++wireworm+control&hl=en.
If you go there you will see in their summary that they believe that, within the variability in their experiment, there was no statistical difference (6% improvement) between the control plot and the mustard treated plot. Damage by slugs, however, was more than halved when following mustard.
 

[Hugh_Jones]

I knew you just wouldn`t be able to resist this one, John.

The actual percentages over 6 blocks averaged as follows:-

(a) On mustard treated ground - wireworm damaged tubers 29%, slug damaged 5.5%

(b) On untreated ground - wireworm damaged tubers 35.5%, slug damaged 13.5%

Although a reduction from 35.5% to 29% is a reduction of 6% in the whole crop, it actually represents a reduction of approximately 18.3% i.e. ((35.5 - 29) x 100) /35.5 in the numbers actually affected

The statement in the summary which you mention did not use the words "no statistical difference", but said "no significant difference" (based on the Genstat 5 Analysis of Variance of the data); the summary continues "There was....a trend for lower levels of slug damage on the mustard treatments......This was also noted for wireworm damage.........Further field experiments with longer periods of pre-planting treatment should be undertaken on certified organic land".

I agree that it is clear that on the basis of statistical analysis used the trials were inconclusive, but at the same time it is clear that the authors considered the subject worthy of further experimentation.

On a more practical level I found some 40 years or so ago that a late summer sowing, simply left over winter, resulted in the virtual disappearance of my wireworm, and I don`t believe that they all naturally and co-incidentally pupated, hatched into click beetles and flew away at the same time.

[Chantenay]

I say chaps, steady on. Your erudition is embarassing me. Thank you for such a fascinating answer.  Wireworm and slugs all with a few little seeds - ain't nature, sorry, ain't science wonderful.
Thanks.

[john_miller]

We have both mis-quoted the reference Hugh. The authors actually say no significant statistical difference (pg.2, 1st paragraph, 3rd line) between the two treatments and the control. While I do agree that the interpretation that you give to the statistical differences, when quoted in that fashion, is significant, the way I am looking at it, and, of course, in my opinion, it is equally valid, is that in every 100 tubers, 6 less will be damaged after mustard cultivation. Spread two equal lots of 100 out, one from each regimen, and no-one could discern the difference, I would imagine. I certainly couldn't.  
Speaking from a commercial point of view, as I tend too, I don't think the difference would allow a subsistence farmer to become suddenly become rich either! Hopefully further research will indeed prove more encouraging. Did you ever try beans? The Annals of Applied Biology is a peer reviewed publication so there must be some replicated experiments that stood up to statistical analysis and were considered successful.

[Chantenay]

I don't do statistics - I failed Scunthorpe School Leavers Maths (a true measure of density) (Amazing - the system won't let me say Scun thorpe as one word - it's my birth town and it's not a rude word.)

How about a good old British compromise. I could do half the intended plot with mustard and half with field beans (because I will want to put potatoes in long before any autumn sown broad beans have delivered)?

[john_miller]

You don't necessarily have to wait for the beans to deliver. They will fix N and probably be releasing the toxic or noxious compounds that control the wireworm from sowing. Harvesting a crop would just be a third part of their benefit. Perhaps you could try companion/intercropping with beans (or mustard) and potatoes, the beans could produce a crop and be removed before you need the inter-row space to hill up? Maincrop potatoes(if that is what you are growing) become receptive to the decreasing daylength necessary for tuber formation 5-7 weeks after planting, depending upon the variety. This critical daylength, by my estimate/guess, occurs in late July in the U.K.. By delaying planting and letting the treatment crop grow on may result in an increased yield, depending upon how much damage you suffered this year.

[Hugh_Jones]

Chantenay, according to L.D.Hills (referred to in the ADAS paper) John and I are both right.  The paper mentions his 1971 book (Grow your own vegetables) as advocating sowing mustard, but in his earlier  (1960) book - Down To Earth Fruit & Vegetable Growing - he advocates (for those who can spare the ground for a full season) a spring sowing of Field beans, followed by a late summer sowing of mustard to clear wireworm from the ground.  However, interestingly, he suggests that a minimum of 8 weeks growth of the mustard should be allowed as against the 6 weeks used in the ADAS trial. Perhaps the authors of the paper had this in mind in their final recommendation.  I would add that it was as a result of L.D. Hills earlier book that I used the mustard treatment very effectively on a wireworm ridden patch - sowing in late summer and leaving it to overwinter, and I suspect that the effects of the mustard increase as the crop ages.

Just on the matter of the mathematics, John, if the trials had shown damage to 17.75% of the crop in the treated sections, would you have considered this a reduction of 17.75%, or (as I would) a reduction of 50%?

Anyway, surprisingly enough, a question on wireworm appears to have thrown up quite unexpectedly a highly efficacious treatment for slugs in the potato patch, and I shall now shamelessly quote the report whenever slugs are mentioned.

[teresa]

Can I ask a basic question please .
If you lime the ground do you get better potatoes and no wireworms?
Teresa

[Hugh_Jones]

No.  If you lime the ground you`ll get very scabby potatoes, but it won`t make any difference to the wireworm.

[teresa]

thanks Hugh,
Thats hubby's idea out of the window.
Teresa

[john_miller]

Of, Hugh? 50%. But a reduction by 17.75%. Or is this echoing Bill Clinton too closely with his trying to figure out when "and" means "and", or something else?
At last you have got something practically useful from this (as opposed to some interesting theoretical work)- I hardly ever see slugs, even this year!

[louise stella]

I have newly cleared ground and have read about growing mustard to get rid of some of the wireworm - do I have time to do this before I put my spuds in????  If not what do you reckon about planting them, with mustard and see how it all goes!!!!  Has anyone ever tried that?

Wishful thinkingly....

Louise