Ask the Master Gardeners: December 2013
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December 1, 2013 | 753 views | Post a comment
Q: I've been cleaning my vegetable garden and pulled up my okra plants. Their roots were just covered with root knot nematodes. I am really surprised because I planted that bed with Elbon rye (cereal rye) two years ago. I thought that was supposed to take care of nematodes. What now?
A: Sadly enough, when I started reading up on the problem, management is difficult. According to the University of California at Davis, you should prevent nematode infestation in the first place by buying resistant plants, making sure the imported soil is not infested, and keeping weeds pulled and your ground sanitary. Once you get nematodes, infestation can be reduced by fallowing, crop rotation, and soil solarization. Each is effective only for about a year. Your garden should have sufficient water and soil amendments to help the afflicted plants. Fallowing means to leave the soil bare for a period of time like one year. For solarization, moisten the soil, cover with clear plastic tarp, and leave for 4 to 6 weeks during the hot summer. Root knot nematodes die when soil temperature gets above 125 degrees for 30 minutes. (The problem, I would think, is how far down that temperature goes.)
There are other nematode suppressive plants besides Elbon rye. French marigolds (Tagetes species) suppress root knot nematodes. Ones that work include Nemagold, Petite Blanc, Queen Sophia, Tangerine, and Single Gold (or Nema-gone). They must be planted solidly--no more than seven inches apart according to Clemson University.
Your best bet is to divide your garden into thirds, and set up a rotation going from fallow, to a summer susceptible crop, to a winter spring crop, to a summer solarizing, and so on. Remember that when you solarize, you kill all of your bugs, both good and bad.
I am now growing all of my tomatoes in their own pot and not in the garden. Luckily, there are some nematode resistant plants. Check the labels on your tomatoes to make sure there is an "N" on the package (Better Boy, Celebrity, etc.) and ask your nursery person about other nematode resistant vegetable plants (leeks, for instance).
Your winter garden will probably do best because most nematode species are active during warm summer months. Remember to remove annual vegetables including their roots just as soon as harvest is over.
Q: As soon as my perennials freeze back can I cut them back to the ground so everything looks neat?
A: Doug Welsh, in his Texas Garden Almanac, says you may cut off dead portions of perennials killed by freezing weather, but if you leave the dead stuff on, it provides some insulation for healthy plant tissue. This pruning is actually best done in February or March.
FYI: Now is the time to collect bags of leaves from your neighbors for your compost bin.
Clara Mae Marcotte is a Texas Master Gardener with Texas A&M AgriLife Extension. If you have a question to be answered, call the Master Gardeners at 830-379-1972 or leave a message to be answered. The website is guadalupecountymastergardeners.org. The Master Gardener research library is open Mondays from 8:30 to noon, at the Mary B. Erskine School in Seguin at the corner of E. Krezdorn and N. River.