Discussions regarding Marigold (Tagetes) and Lucerne
in Tobago
(11/9/01 - 11/13/01)

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postings: 8
countries: Canada, Nicaragua, Tobago (West Indies), United States
organizations/institutions/companies: Eco Project Ltd., Clemson University, CATIE- MIP, AAFC, Cornell University

From: Oliver Ruedel
To: MULCH-L@cornell.edu
Subject: Marigold (Tagetes) and Lucerne
Date: Fri, 09 Nov 2001

Hi,

My Name is Oliver Ruedel, working for Eco Project Ltd., Tobago (West Indies). We’re want to implement a Tropical Organic Farming Research Project with a local NGO, called Caribbean Eco Farmers. On our research site, we want to plant Marigold and Alfalfa as cover crops, for that fore we have several questions. And we would be glad, if you can help us with further information.

1. We want to Marigold as cover crop for nematode control. The questions about Marigold are: do you have experience or information about Marigold as nematode control, which breed of Marigold would you plant in the tropes, where could we get the seeds and which amount of seeds per acre would you suggest to plant?

2. We also want to plant a breed of Alfalfa (Lucerne) as cover crop to enrich soil (nitrogen ) and as humus enhancer. Here the same questions as for Marigold, which breed of Alfalfa would you plant with tropical climate and soil, where to get the seeds and which amount of seeds per acre do we need?

3. And the final question is about rhizobium inocculant, bacteria for nitrogen fixing, we’re not sure if there’re some in the soil. If not we have to inject the soil with these bacteria. Do you know which we need for the tropical soil and where to get it?

So, thank you very much in advance for your help. We are thankful for any kind of information about Marigold and Lucerne as cover crops. Bye

Oliver Ruedel

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Date: Fri, 09 Nov 2001
From: Pezo, Danilo
Subject: RE: Marigold (Tagetes) and Lucerne
To: MULCH-L@cornell.edu

Oliver,

Alfalfa in Trinidad? Do you have the conditions to grow it? Why has it to be that species? Don't you think other tropical legumes could do the same? The diversity of legumes in the tropics is quite rich, and I'm sure you will be able to find more than one candidate to do what you are looking after in your project.

Danilo

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To: MULCH-L@cornell.edu
Date: Sat, 10 Nov 2001
Subject: Re: Marigold (Tagetes) and Lucerne
From: Roland Bunch

Dear Oliver,

My reaction would be the same as Danilo's. Alfalfa is a cold-weather crop which would very likely not grow well at all anywhere in the Caribbean, except perhaps the upper reaches of the Cordillera Central in the DR. Nor is marigold probably the best way of controlling nematodes.

First the nematode issue. Both in Brazil and Honduras, we have gotten very good nematode control with both velvetbean (Mucuna spp) and lablab bean (Dolichos lablab). In fact, all decaying organic matter produces small quantities of chemicals which kill nematodes. Although we are not sure of it at all, we suspect that ANY legume which produces large enough amounts of organic matter (velvetbean and lablab are among those which produce the largest quantities of organic matter among the 15 or so species of green manure/cover crop we use here) will do a good job of controlling nematodes. If that is right, there are five or six species you might try, most of which might have additional benefits that the marygold will not provide. If not, you still have lablab and velvetbean, which would be worth looking into.

As for providing organic matter and nitrogen, once again, there are a whole series of tropical legumes that would produce much more biomass, and fix much more nitrogen, than would lucerne. Would you like to try some of them? If you let us know what crops you are growing and under what conditions (eg what would the farmers most like to receive from their green manure crop--firewood, human food, animal feed, weed control,etc.?), CIDICCO or someone else on the mulch-L list should be able to recommend several promising species to try.

Sincerely, Roland Bunch
COSECHA, Honduras

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Date: 12 Nov 01
From: Bill Rhodes
Subject: RE: Marigold (Tagetes) and Lucerne
To: MULCH-L@cornell.edu

Yes, I agree.

Bill Rhodes

Pezo, Danilo wrote:
>Oliver,
>Alfalfa in Trinidad? Do you have the conditions to grow it? Why has to be
>that species? Don't you think other tropical legumes could do the same? The
>diversity of legumes in the tropics is quite rich, and I'm sure you will be
>able to find more than one candidate to do what you are looking after in
>your project.

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From: Oliver Ruedel
To: MULCH-L@cornell.edu
Subject: RE: Marigold (Tagetes) and Lucerne
Date: Mon, 12 Nov 2001

Dear Danilo,

Thanks for your mail. Do you have any idea what kind of fast growing cover crop, we could use for nitrogen fixation and at same time increase soil humus content. What do you think about Kudzu? Thanks

Oliver

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Date: Tue, 13 Nov 2001
To: MULCH-L@cornell.edu
From: Charles Staver

Mulchers,

Probably the issue of nematode control is worth more discussion. There are different mechanisms for nematode interaction with plants - trapping, repellents, effects on nematode predators. Simply suggesting that any legume is good does not make full use of the available information. we tried to sort out the experimental results of green manure use in plantains and bananas. Mucuna, canavalia, crotalaria - not all were equally effective, but there are several major nematode pests in musaceas and part of the difference may be that different experiments were directed at different nematodes.

In my own case, I had fairly severe problems with nematodes in cowpeas. Based on this experience I would recommend some caution in simply saying that any legume green manure will give nematode control.

Who are the nematologists on line who might give us some references? Or perhaps a simple explanation of how to interpret potential effects?

Charles Staver
Nicaragua

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Date: Tue, 13 Nov 2001
From: John W. Potter
To: MULCH-L@cornell.edu

Hello, Mulchers,

Charles is correct - there are indeed different mechanisms of nematode suppression by plants, and the term 'nematodes' should not be misconstrued to imply that all nematodes behave similarly to all suppressive plants.

For example, marigolds are fairly effective against some of the root-lesion nematodes (Pratylenchus spp.) and root-knot nematodes (Meloidogyne spp.) which invade the roots and burrow deeper into the root than the root cortex. However, a large number of nematode genera are ectoparasites, do not invade the cortex, and are completely uninhibited by marigolds.

Within the legume family, some are susceptible to various root-knot species while others are not. In Canada, we find that alfalfa (lucerne) is not much of a host for the northern root-knot nematode Meloidogyne hapla, whereas clovers (Trifolium spp.) are severely affected by this nematode. Likewise, M. hapla does not invade or survive in grasses, whereas most other Meloidogyne species do.

In general, tropical legumes such as mucuna, crotolaria, dolichos and canavalia are hosts of one or more species of root-knot nematode, and tropical root-knot nematodes are much more devastating to their hosts than are the northern temperate zone species.

The distinction must be made between what the nematode does while the plant is growing, and what happens when the plant is incorporated into the soil. True, leguminous host plants when incorporated often produce nematode suppression, which is related to their nitrogen content. What appears to happen is that the incorporated nitrogenous matter is degraded to release ammonia (which is nematicidal), and also stimulates microorganisms including actinomycetes, many of which release antibiotics which are also nematicidal.

Similarly, many brassicaceous species of plants (mustards, cruciferous vegetables) are host of various nematodes, but when chopped into the soil the residues of these plants release volatile chemicals called isothiocyanates which are nematicidal. Part of the trick of making these work properly is to seal the soil surface so the vapours released from the decaying crucifer tissue do not release into the air before killing the nematodes in the soil.

I would strongly advise anyone who is considering a cover-crop as a nematode control host to first attempt to identify the genus and species of nematode involved. A good general source of information on nematodes is CABI International (www.cabi.org) who publish Nematological Abstracts.

CABI also published (years ago) a catalog of nematode genera and species catalogued under their hosts (authors: Goodey, J.B., M.T.Franklin and D.J. Hooper: "T.Goodey's The Nematode parasites of plants catalogued under their Hosts", 3rd edn. CABI, 1965) which is still an excellent reference if you can find a copy.

I am willing to answer other questions along this line, within the scope of my knowledge. If contacting me, please use the botanical name of the plant species if known, since common names of many tropical plants often are not identifiable to those unfamiliar with them, like myself.

Cheers,

John Potter
(Canada)

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Date: Tue, 13 Nov 2001
To: MULCH-L@cornell.edu
From: H. David Thurston
Subject: Re: Marigold (Tagetes)

Here is a book (132 pp) on nematode control with marigold:

Suatmadjii, R. W. (1969). Studies on the Effect of Tagetes Species on Plant Parasitic Nematodes. Wageningen, Netherlands., H. Veenman & Zonen N. V.

It is difficult to generalize about the use of marigold for nematode control.

Dave Thurston
Dept. of Plant Pathology
Cornell University