Onion biotic stress control

1. Biology and Management of
Stubby-Root Nematodes on
Onion
Review

3. Introduction
• Soil-borne pathogens can cause huge losses to onions resulting in lower
yield in growing season from October to May. In this season soil is usually
moist which can be very favorable for nematode.
• Stubby root nematode(Paratichodorus spp.) is on of the most affective soil
borne pathogen
• It is very critical to Newly emerged seedlings.
• This nematode grow more on sand, sandy loam(coarse textured soil) and
moist soil.
• Optimal temperature for the growth of stubby root nematode is 20 to
30C.
• It is a very devastating nematode and has a wide range from cereals to
vegetables especially during Rabi season. Onion, sugar beet, potatoes and
wheat are major suspect of this pathogen.

4. Introduction
Stubby Root
Nematodes
Female Root knot
Nematode

5. Symptoms
Healthy vs Effected Roots
Left ones show stunted growth
Root Swelling
Yellow, necrotic non-uniform
onion plants

6. Symptoms
• The stunted growth of roots result in poor seedlings.
• Necrotic tips and yellowing in leaves is because stunted and swelled
root are not able to properly uptake the water and necessary
nutrients from the soils, so it indicates the sign of these deficiencies.
• Root prefers more lateral branches.

7. Life Cycle
Female
laying eggs
in soil
Four Stages
of Larvae
Adult
Larva
Attack on
young roots,
root tips stop
growing
Discoloration
of effected
roots
Stunted,
outward and
swelled roots
Poor
seedlings,
yellowing of
leaves
Stirling, Graham & Nicol, Julie. (2020).

8. Management
• Sampling of the soil before sowing the onion is an excellent strategy
for monitoring the population. They are found in upper 6-10 inches of
soils, but not on the top layer of soil.
• Total eradication is not possible.
• During transplantation of onion plant most of the mass is left in the
seed beds due to pulling. After transplantation seed generate new
roots and the old remaining root mass dies, heavily effecting the
nematode population because the only survive in not roots.
• Seedlings damages from transplantation should be avoided for
transplantation.

9. Management
• Heavily infested field should be left fallow.
• Use of resistant cultivars as cover crop in the field. They can also be
used for green manuring.
• Sorghum-sudangrass and hairy vetch should be avoided because the
can increase the population of nematode.
• Soil fumigation before planting onions and non-fumigant nematicides
can help in reducing nematode population.

10. Comments
• As discussed earlier the effects of stunted root nematodes on the
onion and other crops, author has put the light of symptoms, biology
and control techniques of this pathogen, but not much light was shed
on the life cycle of the pathogen, important for controlling a
pathogen.

11. References
• Hajihassani, A., Tyson, C., & Shirley, A. C. of Stubby-Root Nematodes
on Onion.
• Stirling, Graham & Nicol, Julie. (2020). Advisory Services for
Nematode Pests.