Meloidogyne incognita

Meloidogyne incognita It is known as root-knot nematode due to the deformations it causes in the roots of host plants. In some cultures, it is also called root nematode.

Crops attacked

Meloidogyne incognita affects several agricultural crops in Brazil, including soybeans, cotton, tomatoes, melons, pumpkins and other cucurbits.

It is widely distributed and can seriously compromise crop productivity.

Biology

Meloidogyne incognita It has a relatively short life cycle, varying between 21 and 28 days, depending on the soil temperature.

Its cycle includes the following stages:

• Egg: development begins inside the egg, where embryogenesis occurs. Each female can produce 200 to 500 eggs grouped together in a gelatinous mass on the surface of the root. This number may vary depending on the host plant, the nematode population density and soil conditions.

• First stage juvenile (J1): while still inside the egg, the first moult occurs.

• Second instar juvenile (J2): This is the infective stage. After hatching, J2 moves through the soil and penetrates the roots of the host plant. It moves through the cortex until it reaches the vascular cylinder, where it attaches itself and induces the formation of nurse cells called giant cells.

• Third and fourth stage juveniles (J3 and J4): during these stages, the nematode undergoes new molts and increases in size. It becomes sedentary, feeding on the flow of nutrients that circulate in the giant cells.

• Adult: can become male or female. Females are responsible for parthenogenetic reproduction (without the need for fertilization), forming new egg masses in the root of the plant. Males, for the most part, do not feed and have a short life span.

Rapid reproduction and high survival capacity in the soil mean that the infestation can increase considerably from one year to the next, especially if the following crop is susceptible to the nematode.

Ecology and characteristics

Meloidogyne incognita It has a wide geographical distribution and is highly adaptable to different climatic conditions and soil types.

Some environmental factors favor its spread and reproduction:

• Soil temperature: the ideal temperature range for its development is between 25°C and 30°C. At temperatures below 15°C, nematode activity decreases significantly, and above 35°C, its survival is reduced.

• Soil moisture: needs moisture to move and penetrate the roots. Excessively dry soils hinder their mobility, while very moist soils can favor the dispersal of natural enemies.

• Soil type: Root-knot nematodes are more prevalent in sandy or sandy loam soils, where J2 movement is easier. In clay soils, their movement is more limited.

• Survival in the soil: Under adverse conditions, Meloidogyne incognita eggs can remain viable in the soil for long periods, waiting for favorable conditions to hatch. This makes control difficult and reinforces the need for integrated management strategies.

• Alternative hosts: in addition to commercial crops, many weed species act as secondary hosts, allowing the pathogen to remain in the area and making its eradication difficult.

The combination of factors such as high reproduction rate, adaptation to different environments and prolonged survival capacity makes Meloidogyne incognita one of the most destructive plant parasitic nematodes in agriculture.

Damage

Symptoms of a heart attack Meloidogyne incognita include:

• Reduced plant growth;

• Yellowish spots on the ridges in crops;

• Interveinal necrosis in leaves (carijó);

• Pod abortion and early ripening in soybeans;

• Formation of galls on the roots, impairing the absorption of water and nutrients.

In severe cases, productivity losses can reach 100%.

Control

the management of Meloidogyne incognita requires integrated strategies:

• Biological control: Natural enemies, such as nematophagous fungi and bacteria, can be used to reduce populations in the soil.

• Chemical control: specific nematicides can be applied.

• Elimination of host weeds: some weeds also serve as hosts for Meloidogyne incognita, favoring their persistence in the area.

• Crop rotation: alternating with non-host species, such as peanuts and resistant genotypes of corn and sorghum, can reduce the nematode population.

• Use of green manures: species like Crotalaria spectabilis and black mucuna contribute to reducing the pathogen populations.

• Use of resistant cultivars: Genetic improvement has made resistant cultivars available for crops such as soybeans, cotton and melons.

The combination of these strategies is essential to minimize the impacts of this phytonematode on agricultural production.

To learn more about Meloidogyne incognita, click on:

• Reaction of weed species to the nematode "Meloidogyne incognita"

• Nematode promotes reprogramming in tomato plants

• Alternative control of root-knot nematode in soybean crops

• Managing nematodes in cotton

• Integrated management of nematodes in melon trees

• How to combat nematodes that affect soybean crops

To find out which pesticides are registered for control, click on nematicides against Meloidogyne incognita