Close this search box.

Root-knot Nematode | Symptoms & How to eliminate

With the continuous development of facility agriculture, root-knot nematode disease has become one of the diseases that seriously threaten food production.

Root-knot nematodes are parasitic nematodes in the root system and belong to animals without vertebrae. They have strong resistance, adaptability, and reproduction ability. It multiplies on the roots and spreads germs, which is difficult to control. In addition to leeks, garlic, and green onions, other vegetables such as melons, solanaceous fruits, beans, and leafy vegetables are all affected.

Moreover, it will generally reduce the yield of vegetables by 20% to 30% and severely lead to no harvest.


The life cycle of nematodes is divided into three main stages: egg, larva, and adult.

1. Eggs

Root-knot nematode eggs are cocoon-like, relatively transparent, they have a tough outer shell, about 0.1 mm long and 0.05 mm wide.

2. Larva

The 1st instar larva curls into the egg after hatching.

The 2nd-instar larvae enter the infection stage. After invading the host, their body gradually expands and changes from linear to pod-like.

The 3rd instar larvae resemble eggplants and begin to differentiate between male and female.

The 4th instar larvae have completed the male-female differentiation, the females are eggplant-shaped or pear-shaped, and the males are curly-curved.

3. Adult

The male adult is linear, with a slightly rounded tail, transparent in color, and small in size.

Adult females are pear-shaped or lemon-shaped, milky white, and are mostly buried in root tissues.

Symptoms of Root-knot Nematodes

Under the Ground

symptoms of root-knot nematode

Root-knot nematode symptoms on plant roots are dramatic. However, most diagnostic root-knot nematode damage occurs underground. By identifying these underground symptoms, we can know whether root-knot nematodes have already threat your crops.

The most distinctive symptoms of root-knot nematodes infestation is the appearance of galls on primary and secondary roots, which become swollen and distorted with heavy infestations.

On the Ground

Besides the symptoms of underground, root-knot nematodes infestation also have other above-ground symptoms. Root-knot nematode damage results in weak growth, a decline in quality and yield of the crop, and reduced resistance to different stresses. Seriously may lead to direct death.

  1. Stunted, yellowed, or wilted, and can lead to the premature death of the plant. (Symptoms on tomato)
  1. A sharp drop in output  (Symptoms on potatoes)
root-knot-nematodes on leaf
root knot nematodes drop in output

What Causes Root-knot Nematodes

1. Excessive fertilization will reduce the beneficial bacteria in the soil, increase the harmful bacteria, and acidify the soil.

2. Apply uncomposted manure.

3. With the change of temperature and humidity and the application of pesticides, nematodes move repellent in the soil.

4. Root-knot nematodes can be transmitted through natural mobility such as diseased soil, diseased roots, wind, rain, and irrigation. They can also be transmitted through agricultural operations and personnel walking.


1. Nematodes absorb nutrients in plants and affect their normal growth. As a result, plant growth is weak, leaves are yellow, fruit trees grow poorly, roots are not developed, and nutrient absorption is further affected.

2. The secretions from the metabolic process of nematode infestation directly stimulate plant cells and tissues, which further leads to poor plant growth, plant deformities, and affects the yield and quality of agricultural products.

3. Due to poor plant growth and poor resistance, the incidence of other diseases and insect pests have risen sharply, and the ability to resist natural disasters also decreases.

4. In addition to the diseases caused by nematodes, nematodes can also spread other diseases, such as bacterial diseases, viral diseases, and fungal diseases. There are many other pathogens in the soil after the roots are infected by nematodes, they are susceptible to other pathogens, which aggravates the occurrence of diseases.

How to Eliminate

Before the extensive use of chemical fertilizers and pesticides, nematodes also existed, but they did not harm crops.

However, in recent years, due to the extensive use of chemical fertilizers and pesticides, the soil ecological balance has been severely damaged.

For example, the extensive use of fungicides reduces the food source of nematodes (a considerable number of nematodes feed on bacteria), acaricides eliminate the mites that prey on nematodes, and so on.

There are many ways to control nematodes, but in fact, the effect of preventing nematodes is getting worse and worse, which makes nematodes more and more evolved. The fundamental reason is that the soil balance is destroyed. To restore the soil to a healthy state, you need to properly improve the soil pH, add beneficial microorganisms, apply decomposed organic fertilizers, and improve the soil’s water vapor cycle.

On the defense of nematodes, we can also try:

1. Strengthen inspection and quarantine, and try to reduce or even eliminate the transmission of root-knot nematodes through seedlings, machinery, tools, and other human factors.

2. Reasonable rotation can reduce the number of soil nematodes and reduce the occurrence of diseases.

3. Treat sick strains thoroughly and fertilize and water rationally.

4. Select anti-root knot nematode varieties or choose root-knot nematode rootstock for grafting.

Leave a Comment

Scroll to Top
WhatsApp Us