Q. I was going through my garden notes and I
found pictures I took a few months ago of my tomato plants. A few of them came up with real gnarly roots,
I have never seen anything like it.
A. This is definitely root knot nematode judging
from your photos. There really is no way to totally rid the soil of nematodes.
In the past, soil fumigants were used on a regular basis to knock these
critters back. Soil fumigants are being eliminated from the pest control
arsenal due to environmental concerns.
Your options are to move your growing area to a
new location that is not infested, grow in raised beds or containers and use
resistant varieties. There are some vegetable varieties more resistant to
nematodes than others.
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| Roots of tomato plant from reader |
Use varieties that have a capital “N” after
their name. This stands for “nematode resistant”. An example would be the
tomato, Better Boy VFN which is resistant to Verticillium and Fusarium diseases
as well as nematodes.
Build up your organic matter content with lots
of compost. Nematodes don’t like soils with high organic matter.
Be very careful of transferring soils
contaminated with nematodes to new beds or containers. This includes using contaminated
gardening utensils. Make sure utensils are sanitized between locations.
It is possible for this pest to migrate from your
existing soil to a new raised bed constructed on top of contaminated soil. You
might to consider laying thick plastic underneath the raised bed. Make sure the
plastic is sloping slightly for drainage and make the bed at least 12 inches
deep.
Here are some links back to my blog where I have
written about nematode in the past.
Ann Edmonds who heads up the Master Gardeners program for So. Nevada discovered nematodes in her yard. She has put a lot of time into attempting to find out the best ways to deal with them. Since nematodes are super tiny worms who enjoy moist soil like most worms do, she has decided to dedicate the area of the yard to desert plants since a dry soil will not support nematodes. Solarizing the soil by placing clear plastic sheeting over the soil for an entire summer will sterilize the soil and may rid the soil of most of the nematodes but it is very hard to guarantee complete eradication.
ReplyDeleteThree years ago, we placed a raised bed about 6 feet from the palm, it is about a foot deep and a foot above ground level. For the 2013 season, all the indigenous soil was replaced with Viragrow and vegetables were planted in it, including an Early Girl tomato. It grew well but did not thrive. At the end of the season I removed all the plants and identified nematode damage on the tomato roots.
ReplyDeleteSeveral weeks ago, I was cultivating the raised bed, when the cultivator encountered significant roots, leading to the direction of the date palm. The roots show damage of nematode knots, similar to the damage seen on the tomatoes of last year.
On the internet, I found that nematode infection is known in date palms, and that the only treatment for the home gardener is to add organic matter to the soil which I thought Viragrow had. Pesticides are not available to the home gardener. I plan to grow plants resistant to nematodes in the raised bed. In your experience are there other alternatives?
I was reading between the lines of your email and it sounds like you may be suspicious that the nematodes were brought in on the date Palm.
DeleteRegardless of how they got there, it appears you have them. There is nothing you can do to eradicate them from the soil. Instead, we focus on nematode management. There are several strategies you can attempt.
Grow vegetables more tolerant of nematodes. This includes sweet corn, asparagus and cool season crops in the cabbage family such as broccoli, kale, collards and mustards.
Compost. High organic matter percentages make the soil less desirable for nematodes. It will not kill or stop nematodes but it helps manage their populations. This is because there are several soil microorganisms that feed on nematodes which are stimulated by the addition of organic matter such as compost. These soil microorganism populations are encouraged with additions of compost. Viragrow has several products ranging from straight compost to soil mixes that contain compost. Make sure that you use the 100% compost product and not a soil mix which may only contain about 35% compost, the rest is sand and other ingredients.
Clandosan is a soil amendment that discourages nematodes and has been around for over 20 years. It works in a similar way to additions of compost. Clandosan is a byproduct from the fishing industry made of crushed lobster and oyster shells. This soil additive encourages several soil microorganisms that feed on nematodes.
Use resistant varieties. You already know about these but make sure varieties of vegetables that you select have the letter “N” after their name which designates they are nematode resistant. This does not mean they will not get nematodes but they are less likely to be severely damaged by nematodes than those vegetables which are not designated with an “N”.
Plant trap crops. Some crops like squash are nematode magnets. Putting a few of these in the garden area act as preferred feeding sites for nematodes. Planting of trap crops is believed to be a good strategy in nematode management.
Plant French marigolds. There is a residue produced by the roots of French marigolds that discourage nematode development. Planting these throughout your production area may help to discourage their populations from developing.
Soil solarization. Digging and loosening the soil during the summer between crops and covering this loose, moist soil with clear plastic can help generate temperatures close to 200° F. These high temperatures will kill nematodes. After three or four days of clear skies and high temperatures, remove the plastic and redig the area with sanitized gardening tools. Moisten the soil lightly and reapply the plastic for another 3 to 4 days. The nematodes will come back but this will reduce their numbers at the time of planting.
Sanitation. Make sure all of your garden tools are cleaned and sanitized when working in this area. Nematodes can be distributed by humans on dirty garden tools.
General plant health. Keeping plants fertilized and irrigated so that they are vigorous helps you get some production even though plants are infected. This strategy focuses on making plants vigorous long enough to produce even though they are infected. I would stay away from perennial crops unless you know that they are nematode resistant.
Even though this is focused more on the commercial producer, you might find this interesting reading
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7489.html
good luck!