Nematode management starts a year before planting a susceptible crop like fruit trees. Try to reduce nematode populations so that clean stock can establish well before the nematodes rebound to damaging levels. Young plants tolerate much less nematode feeding than established plants. Use a combination of the following methods to manage nematodes:
- Start new fields with transplants free from nematodes and grown by an accredited plant propagator.
- Rotate susceptible crops with non-host crops for several years.
- Grow nematode-suppressing cover crops in the years prior to establishing fruit crops.
- Destroy residual crop roots.
- Plant resistant fruit cultivars where available.
- Control weeds, as they are good hosts of nematodes.
- Use soil fumigation before planting when nematode populations in soil reach or exceed thresholds. For a list of registered preplant fumigants, see the fruit crop protection search.
Cover Crops for Nematode Suppression
Cover crops may reduce populations of plant parasitic nematodes when properly managed in the year before planting. In Ontario, these nematode-suppressing cover crops have been successful:
- oilseed radish
- certain white and oriental mustard cultivars like White Gold, Pacific Gold, Caliente, Cutlass or Forge • specific sorghum × sudan-grass hybrids
- African marigold cultivars like Crackerjack or Creole
- Canadian Forage Pearl Millet 101 (root-lesion nematode suppression)
Not all cultivars of the above cover crops reduce nematode populations. Choose the right variety. One or more years of nematode-suppressing cover crops may be required to reduce nematodes below economic thresholds.
Cover crops suppress nematodes in different ways:
- Canadian Forage Pearl Millet 101 is a poor host and inhibits the ability of root-lesion nematodes to reproduce in its root-system.
- Certain cultivars of African marigolds produce a root exudate that is toxic to nematodes in the soil.
- Nematode-suppressing cover crop cultivars of brassica plants (e.g. oilseed radish, certain white and oriental mustards) produce glucosinolates and an enzyme in their leaves, stems and petioles. When the cover crop is cut and immediately incorporated into the soil, the glucosinolates are converted into isothiocyanates, which are toxic to nematodes.
Exclude cover crops such as clovers and buckwheat from orchard rotations. These are excellent hosts for root-lesion nematodes. Wheat or barley are the best cereal crops to grow before planting.
For more information, visit ontario.ca/crops and search the Soil Management, Fertilizer Use, Crop Nutrition and Cover Crops for Fruit Production webpage.
Other Cultural Practices to Reduce Nematodes
Nematode populations can build on many weed species. A good weed control program is essential the year before planting fruit crops. Plan an intensive weed management strategy for the cover crop where nematode-suppressing cover crops are grown.
Keep land fallow the year before planting to reduce nematode numbers. A disadvantage to fallow land is increased susceptibility to soil erosion.
In orchards, choose ground covers for planting between the rows that do not support nematodes, such as annual or perennial ryegrass, or creeping red fescue.
Nematode Suppression After Planting
Velum Prime is a broad-spectrum nematicide/fungicide (Fungicide Group 7) with preventative, systemic, and curative properties for the suppression of certain soil plant pathogenic nematodes and control of certain crop diseases. Velum Prime is best suited for use in a preventative treatment program. For best results, this product should be applied in the root zone through drip irrigation equipment only beginning at planting. As the roots take up the product, it suppresses root feeding nematodes and moves up into the foliar plant tissue to control certain fungal diseases such as powdery mildew.
- To limit the potential for disease resistance developing to Group 7 fungicides, do not make more than 2 sequential applications of Velum Prime or any other Group 7 product before rotating to a different fungicide group registered for the same use.
- Fungicides other than Group 7 with a different mode of action should be applied for the first foliar fungicide application.
- Do not apply more than 1 litre of Velum Prime/ha per year, regardless of formulation or method of application.
- Maintain a minimum 30-day interval between soil applications.
- Velum Prime can be applied up to 7 days preharvest.
Vydate will suppress nematodes after planting non-bearing apples. Vydate is less effective than pre-plant soil fumigation and does not control soil-borne disease. Refer to the product label for application methods, mixing instructions, rates and precautions.
- Vydate is highly toxic to bees. Do not apply during the pink or bloom period.
- Vydate is very toxic to humans. Follow application instructions closely.
- Treat young whips and non-bearing fruit trees with 1 application of Vydate as a soil drench around the base of each tree when roots are actively growing and leaf growth begins in the spring. Follow this with a foliar application of Vydate.
- An alternative method is to make 3 foliar applications on a 2–3-week schedule for a total of 3 applications.
- Do not allow spray to drift onto trees in bloom.
- Do not apply to trees under water stress or not actively growing.
- Do not re-enter treated fields for 24 hours after application.