Publication 360, Guide
to Fruit Production: Nematodes
Excerpt from Publication 360, Guide to Fruit
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Other topics in Other Pests and Disorders
Chapter 9 - Other
Pests and Disorders - (PDF
Introduction & Symptoms
Plant parasitic nematodes can cause significant yield losses to
many horticultural crops. The extent of loss depends on the crop,
nematode species and soil populations.
The most destructive and common nematodes in Ontario fruit crops
are root-lesion (Pratylenchus penetrans) and northern root-knot
(Meloidogyne hapla). The northern root-knot nematode is becoming
more prevalent. The pin (Paratylenchus sp.) and dagger (Xiphinema
sp.) nematodes occasionally cause yield losses to some fruit crops
in isolated fields. The dagger nematode is mainly a virus vector
on grape, raspberry and apple.
Symptoms of nematode injury include:
- uneven plant growth
- poor plant establishment
- weakened plants over time
- poor root growth
- knots or galls on roots
- excessive branching of roots, hairy root symptoms
- Root-lesion nematodes cause discolouration of the fine feeder
roots and tiny, brown, scratch-like lesions on the young white
roots. These lesions merge to form large brown areas. Root-lesion
nematodes are involved in black root rot and aggravate verticillium
wilt of strawberries and other host plants. Severely infected
plants appear stunted and unthrifty.
- Root-knot nematode feeding stimulates root cells to enlarge.
Enlarged cells look like small galls or beads (1 mm). As more
and more nematodes establish feeding sites, they join together
to become one larger root-knot.
- Root-lesion nematode feeding causes scratch-like lesions on
roots, similar to the symptoms on strawberry roots. Severely infested
plants have thinner and fewer canes per crown. Up to 25% of first
year canes may be killed by severe infestations of these nematodes.
- Dagger nematodes spread tomato ringspot virus, which causes
crumbly berries, mottled leaves and cane dieback.
On tree fruits:
- Root-lesion nematodes can be a major cause of orchard replant
failures. They can cause a decline in vigour of existing peach
and cherry orchards. These nematodes cause small brown lesions
on the white lateral roots and kill the fine feeder roots. When
lesions merge, the entire root system appears discoloured. Root
lesions are frequently invaded by other pathogens which can cause
root rot. Severely affected trees may lose all feeder roots; young
replant trees may die. Existing trees lack uniformity.
Nematode populations above economic thresholds can significantly
reduce yields. The economic threshold for nematode populations
refers to the population at planting. Planting a susceptible crop
in soils with a population of nematodes near or above the population
threshold will result in crop losses over time. For economic thresholds
see Table 9-1. Thresholds for Nematodes on Fruit
Type of nematode
Control with levels reach
| Root-lesion nematode
1,000/kg soil - (exception: 500/kg soil
|Bulb and stem
For more information, see OMAFRA
Factsheet, Sampling Soil and Roots for Plant Parasitic Nematodes,
Order No. 06-099.
Information on how to sample soil for nematodes and
where to send the samples is found in Appendix
D. Diagnostic Services.
For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047