Just curious, but have marigolds lost their effectiveness against nematodes?
Shouldn't it still be useful to plant smelly French marigolds around the base of any of the worst affected plants (at least in smaller-sized plots) and later till under the old, bloomed-out marigolds once they've passed their prime, to incorporate some further residual protection into the soil?
Bulk marigold seed should not be all that expensive.
Just pondering marigolds as an alternative option for the smaller fruit grower of whom there are many here on TFF . . .
Paul M.
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I have not researched marigolds much, but I believe they do have an effect. Unfortunately, I think that (like jack bean) they would need to be incorporated into the soil to be effective. This reduces the effectiveness for already established tree crops. I think these types of plants work best as cover crops and prior to planting an orchard.
There are several reasons I have been focusing on jack bean. 1). It has proven highly effective at reducing nematode populations (you will notice that plants in the study varied in effectiveness). 2). It fixes nitrogen in large quantities. Actually, it had the highest reported level of nitrogen fixation of any of the plants that I looked at (3-4 times the level of cowpeas in a year's time). 3). It can be grown without irrigation durring our summer "off season" for vegetable crops. This allows the same space to be used for my garden in the fall. 4). There are some other studies out there showing that jack bean can also reduce other soil pathogens and that it may even be possible to create an organic herbicide form seed extract.
I guess I am just really excited about this particular plant. Lol!