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Nematodes

When you can’t rotate your crops to avoid nematodes

( You probably have nematodes and don’t know it )

My test beds had an unusually high number of Root Knot Nematodes last summer that were evidenced by smaller fruit and lumpy and bumpy roots on my tomato plants, peppers, eggplants, etc.  And altho’ I don’t grow carrots and other root crops these will also appear as misshapen and lumpy if you have nematodes.  You may not know this but, , , you probably have nematodes in your soil.

This nematode population increase is caused when crops are not rotated, as is recommended in farming.  Which is a problem for we who garden in small yards and can never rotate crops.  Most of the advice we receive for nematode control is directed to farmers, after all, their harvest is much more important than our small backyard harvests, they feed the nation.  Right ! Tell that to my husband who has been waiting for one of my big juicy tomatoes for his sandwich.

For those who don’t know what a nematode is I will tell you . . . then I’ll tell you what I have done to control them.  Then I’ll tell you why I did this.

Nematodes are very small worms, a microscope would help to see them.  But don’t bother looking for them, it is easier to find them by the damage they do.  Nematodes spend most of their life inside the roots of many veggie plants and lay up to 1000 eggs in the soil near the roots.  These eggs are in an egg sac or egg mass to keep them moist.  When the eggs hatch the babies move to establish a home in the vascular tissues of roots.  Usually entering near the tender tip of roots to eat.   This invasion interrupts the plant from getting nutrients.

Their life cycle may be completed in 17 to 57 days and the eggs and larvae can be spread from bed to bed when we use the same gardening tool without washing it off before going to the next bed. Including our garden gloves, hands, shoes, etc., and those of landscapers and from transplants taken from another garden or from dirty pots.

Nematodes, larvae and eggs, will over-winter in moist soil and in and on the roots left in the soil and in the roots of weeds.   When the weather warms in spring we come along and feed them our new veggie plants we have carefully purchased or grown from seed.  We are so good to the nematodes to do this year after year, so they thrive and populate our beds.

Damage that occurs can be viewed by looking at the growth of the plant.  It is a plant that is not doing very well.  The fruit is smallish or the plant may be stunted, have yellow leaves, and no amount of fertilizer seems to do any good.   Sometimes it just keels over and dies.  Pull up one sick plant and look at the roots, after all, you planted several and you need to know what’s going on in the soil.  If it’s nematodes the roots are lumpy and bumpy.  If there are no nematodes in the roots and you pulled the plant out carefully, you can stick it back in . . . you have another problem to diagnose.

The interesting thing about Root Knot Nematodes is that they are aquatic creatures, which means to me they need a moist environment to survive.  When I found this tidbit of information it seemed obvious to me that we desert gardeners have a natural control.

So, how CAN we get them under Control? Here’s what I did to kill off the nematode population in my test beds.  The Water District is going to love me for what I’m about to tell you to do.

1. I pulled up the veggie plants right after I was done harvesting in the fall, I pulled out the roots especially and put them in the trash to be hauled off to the dump. . . . after all, the roots were full of nematodes. ( I don’t have weeds, but if you do pull the weeds too. )

2. I completely shut off the irrigation to the test beds so the soil would be dry for weeks. . . . powder dry.  I only had one season to go through without my cool season veggies like spinach and lettuce. . . . small sacrifice since Trader Joe’s has good prices on these.

3. In the late winter and early spring I began to add to the soil a mixture of 50% leaf compost and worm castings so that I ended up with 1/2 original soil and 1/2 a mixture of compost and worm castings.  Then I turned on the irrigation to the beds.  Boy ! Do I have some rich and fluffy soil ? ?  I can reach down into it up to my armpit . . the roots of my plants love this stuff.

The reason I pulled the veggies up as soon as I picked my last veggie was because, I knew the nematodes were mostly still in the roots and it seemed like a good way to get rid of a bunch of them all at once.

The reason I turned off the water until the rains came, was to dry out any nematodes, larvae and eggs that didn’t come out with the roots of the summer veggies.

The reason for adding the fresh compost and fresh and moist worm castings is because I want the microbial activity to kill the nematodes, larvae and eggs that were in the soil when I pulled up the plants, those nematodes that may not have experienced a crispy death in the powdery dry soil last fall and winter (this was a test and I wasn’t sure).  Certain microbes in fresh compost will kill nematodes.

These microbes also make the nutrients in this new soil available to the roots.  The fresh compost and worm castings have added more ’tilth’ to the soil and made it loose and fluffy so the roots can happily go here and there and wherever to get lots of good food.

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