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Time to Plant Warm Season Cover
Crops for Nematode Control
Now that the soil and air are both warm, it's time to plant cover crops
for nematode suppression. Cover crops like pearl millet, marigold and
sorghum sudan (make sure you have the right variety though for the sorghum
eg. Sordan 79 or Trudan 8) can reduce nematode numbers in the pre-plant
year for strawberries or in preparation for orchard replanting . When
cover crops are used to reduce nematodes, the goal is to establish actively
growing, pure stands of these cover crops. Planting and establishment
must be focused on getting a dense stand and achieving the most top growth
possible.
- Seedbed - should be worked to give a fine, level seedbed in
good condition - all of these seeds will have problems getting through
a crust.
- Seed - seeding rates are
- Pearl millet - 12 kg/ha (10 lbs/A)
- Sorghum sudan - 12-40 kg/ha (10-36 lbs/A)
- Marigold - 1.3 kg/ha (1.1 lbs/A)
- Planting
- Drilling in the seed would be the best option for planting, as
both depth and distribution are more controlled with a drill which
is critical under dry soil conditions.
- If broadcasting the seed - use a slightly higher seeding rate
to compensate. To improve distribution you may want to halve the
rate but spread twice. Not every seed will fall into good conditions
with a broadcast application. Nematode suppression from cover crops
is dependent upon a consistent, dense, weed free, actively growing
cover crop.
- Marigold is particularly difficult to seed - the feathery tails
get a static charge and stick together and to everything. In Ontario
projects with marigolds, rice helped the seed flow considerably.
- Incorporate and firm the seedbed - The key is to have good
seed to soil contact without burying the seed too deeply. Millet and
sorghum-sudan can take being ½ inch deep or a bit more as long
as the soil does not crust.
- Host range for root lesion nematode - Root lesion nematodes
feed on over 500 host worldwide including many vegetable, berry and
fruit tree crops as well as several weed hosts such as nightshade, burdock,
dandelion and plantain. They will also survive and reproduce in some
weed hosts such as ragweed, lamb's quarter and pigweed, however, these
plant species are not preferred host for this pest. Weed management
is very important in fields planted with nematode suppressive cover
crops since the nematodes will migrate to weed hosts on which they feed
upon and reproduce, thus negating the suppressive effects of the cover
crops.
- Weed management - Obviously controlling weeds is very important
to achieve maximum nematode suppression. Where possible, using the stale
seedbed technique will greatly reduce weed pressure. This means that
the sites should be worked as soon as possible, and weeds allowed to
germinate over several weeks. Just before planting, weeds can be killed
down by Roundup, Ignite or Gramoxone (or flaming if available). Seed
can be direct drilled or spread on top. Harrowing may be necessary to
get seed-soil contact, but this tillage will bring new weeds to the
surface. Where drilling is used, and if weeds emerge before the crop,
Gramoxone or Ignite could be used to kill off existing weeds (Note:
using a plate of glass on the soil surface will give you a couple of
days notice on when the cover crop will emerge.
- Herbicides - for Sudan-sorghum and pearl millet, postemergent
herbicides could be used.
- See Publication 75, Guide to Weed Control under Forage crops. Pardner
@ 1 L/ha or 2,4-D Amine 600 @ 0.5 to 1 L/ha can be applied after the
crop has reached 4 leaves.
-
See Table 10-1 to see what weeds will be controlled by each herbicide.
For example, Pardner is stronger on lady's-thumb and ragweed.
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Basagran or Peakplus can be used at an earlier stage of growth.
There may be some recropping issues with Peakplus - it has a 22
month interval for alfalfa, but no information on apples.
Learn more:
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For more information:
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Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca
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