Marigolds for root-knot nematode control

weedlady(Central OH 6)February 18, 2013

Does this seem nuts to anyone but me? According to the chart at the NC Dept of Ag Center (link below), in order to achieve results the second year from planting either Tagetes erecta or T. patula marigolds (the only 2 species effective for nematode control), one must plant 300 (yes -- three HUNDRED) marigold seeds in a 100 square foot plot! Three hundred marigold plants in a ten by ten foot area??? In my experience, planting marigolds even one foot apart would result in complete ground cover (and the roots would intertwine below ground), and would certainly take nowhere near 300 plants!!
Comments?
http://www.oisat.org/downloads/nematodemarigold.html

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tsugajunkie z5 SE WI

Yep, that's what I've read as well. Planted cheek by jowl to make nematodes howl. ;-)

tj

    Bookmark   February 18, 2013 at 5:49PM
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ken_adrian Adrian MI cold Z5

first.. you are in OH .... why are you dealing with NC???? that cow palace OSU ought to have info for you ... lol

regardless.. you would NOT buy and plant PLANTS... too much $$$$

you would buy bulk seed.. and germinate a ground cover ...

ken

    Bookmark   February 18, 2013 at 6:12PM
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calliope(6)

We most definitely do have root-knot nematode in Ohio, Ken. LOL at calling OSU a cow palace. I studied Hort there, and I've heard Columbus called a big cow-town before, but when we come up from the sticks to the big city, they think of themselves are cosmopolitan. Yes, it takes a big bunch of marigold to combat them, but the preferred treatment is crop rotation. If you leave the ground fallow for three years or plant species they don't parasitise, you can presume the soil is free of them and return to your normal crop.

    Bookmark   February 18, 2013 at 7:17PM
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calliope(6)

We most definitely do have root-knot nematode in Ohio, Ken. LOL at calling OSU a cow palace. I studied Hort there, and I've heard Columbus called a big cow-town before, but when we come up from the sticks to the big city, they think of themselves are cosmopolitan. Yes, it takes a big bunch of marigold to combat them, but the preferred treatment is crop rotation. If you leave the ground fallow for three years or plant species they don't parasitise, you can presume the soil is free of them and return to your normal crop.

    Bookmark   February 18, 2013 at 7:18PM
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calliope(6)

I always wondered how folks got double postings, and it happened to me. It's those dang ads hanging and timing the page out.

    Bookmark   February 18, 2013 at 7:20PM
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jean001a(Portland OR 7b)

Well, even with years of fallow or tolerant plants, you're still likely to have nematodes in the soil. They'll be at lower than previous numbers but will start rebuilding their populations as soon as you plant a susceptible crop.

When the marigolds are used, the nematodes will infest the roots but won't be able to multiply. The marigold planting must be for an entire season with no other plants in the affected area.

The common notion that one can interplant marigolds to prevent, or limit, RKN infestions is nonsense.

Jean
who gardened for 30-some years in SoCal, all the while dealing with plant damaging RKNs.

    Bookmark   February 18, 2013 at 8:57PM
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weedlady(Central OH 6)

Ken--who said anything about buying marigold plants? I rarely have even bought marigold seeds in my life; they are best snithered from a friend or neighbor or even a street planting. :-) I plant them just for the spots of color and to bring in the odd pollinator among the veggies.

And I am not "dealing with" NC (or RKNs). Happened to Google RKNs (cannot now even recall why; maybe I just happened across the NC website en route to something else). Just was struck by the vision of 300 marigold plants in 100 sq ft... Surely none of them would be very vigorous.

    Bookmark   February 18, 2013 at 10:16PM
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Kimmsr(4a/5b-MI)

Much of what I read in that article I learned back in the 1970's, some cultivars of Marigold can help control some nematodes. Like other things in your garden you may not want total control of nematodes since some are beneficial and some are even predators.

Here is a link that might be useful: About Nematodes

    Bookmark   February 19, 2013 at 6:45AM
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rhizo_1 (North AL) zone 7

The beneficial nematodes will not be affected by marigolds, kimmsr. Only the plant parasitic species.

    Bookmark   February 19, 2013 at 7:53AM
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Kimmsr(4a/5b-MI)

That, Rhizo, implies that the substance in the Marigold roots that controls the nematodes can distinguish between good and bad nematodes just as some people seem to think that certain pesticides can distinguish between insect pests and beneficials. It just does not happen that way.

    Bookmark   February 21, 2013 at 6:51AM
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rhizo_1 (North AL) zone 7

I'm very interested in your theory, kimmsr. Please link some data that supports it....I would sincerely be appreciative. Will look forward to it.

One thing that hasn't been mentioned as yet is that a soil test (nematode assay) should come first. Not all plant parasitic species will be effected by marigolds. Contact your local extension for information on this specialized test. There are several different RK species, for example....not all are susceptible to marigold's chemistry.

Once the inventory has been done, you'll be better prepared to match up the right marigold.

    Bookmark   February 21, 2013 at 6:23PM
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