Nematode Threatens Crops (By: Dr. Prashant B. Kale)

Nematode Threatens Crops

Author: Prashant B. Kale (Ph.D.)

On our farm, as a farmer, we grow oranges. We have chosen to cultivate brinjal plants in between orange plants to generate additional income. However, we have observed that brinjal plants are showing signs of a root-knot nematode attack. This is being observed in images.

Table of contents:

• Background case
• Nature of loss
• Integrated management activities:

A. Crop rotation practice

B. Soil solarization technique

C. Biological control by beneficial bacteria and fungi

D. Predatory insects and nematodes

E. Cover croping & green manures 

F. Soil amendments

G. Soil management practices

H. Nematicidal chemicals

• Note

Root-knot nematodes invade the roots of the plants, causing the formation of small, swollen knots or knots. These galls disrupt the normal functioning of the root system, leading to poor nutrient and water uptake by the plant. As a result, the affected brinjal plants exhibit stunted growth, yellowing of leaves, wilting, and a general decline in health.

Root-knot nematodes (Meloidogyne spp.) are microscopic roundworms that commonly attack a wide range of plants, including brinjal (eggplant). These nematodes can cause significant damage to the roots of plants, leading to stunted growth, wilting, and reduced yields.

The presence of root-knot nematodes in brinjal plants is a cause for concern, as it can severely affect the yield and profitability of your short-term brinjal crop. If left unmanaged, these nematodes can persist in the soil and continue to infest subsequent crops, including your orange plants, potentially leading to further economic losses.

When the nematodes infest the roots of the orange plants, they can lead to the formation of galls or knots, similar to what happens in brinjal plants. These galls disrupt the normal functioning of the roots, impairing nutrient and water uptake by the orange tree. As a result, the orange tree may exhibit stunted growth, reduced vigor, yellowing of leaves, and decreased fruit production.

To address the root-knot nematode infestation, there are several management strategies. Integrated nematodes management practices are much more helpful therefore one can consider the following activities:

1. Crop rotation practice: 

By avoiding plantation of brinjal or other susceptible crops in the same area for consecutive seasons. Rotation with non-host crops can help break the the life cycle of nematodes and reduce their population in the field. 

Soil solarization technique: this involves covering the soil with transparent plastic during the hot summer. This activity will raise the soil temperature and kill nematodes and other soil born pests.

C. Biological control by beneficial bacteria and fungi: certain bacteria and fungi have been observed to have antagonistic effects against nematodes. For instance, Bacillus subtilis and Pseudomonas fluorescens (beneficial bacteria) produce some toxic compounds to nematicides. Some compete for resources, ultimately suppressing the population of plant pathogenic nematodes. Fungal species, Trichoderma and Paecilomyces have shown potential in reducing nematode populations.  nematode-trapping fungi can be used to suppress nematode populations. One can consider the introduction of these organisms into the soil to combat the root-knot nematodes. 

D. Predatory insects and nematodes: Some species of insects and even nematodes are known as predatory nematodes. These are known to feed on plant-parasitic nematodes. Example: members of Steinernema and Heterorhabditis are predatory nematodes, infecting plant-parasitic nematodes and effectively reducing their numbers.

E. Cover cropping & green manures: Planting specific cover crops or incorporating green manures can help manage nematodes. Some plants, such as marigolds (Tagetes spp.), produce compounds that can repel or inhibit nematode activity. Other plants, like mustard (Brassica spp.), can release chemicals that are toxic to nematodes. Planting these crops in rotation or as cover crops can help reduce nematode populations.

F. Soil amendments: Certain organic amendments, such as compost, biochar, and neem cake, can improve soil health and create an environment less favorable for nematode survival and reproduction. These amendments can enhance beneficial microbial activity and nutrient availability while suppressing nematode populations.

G. Soil management practices: maintaining proper drainage, improving organic matter, and avoiding excessive soil compaction can help create a healthier soil environment that is less conducive to nematode infestations.

H. Nematicidal chemicals: nematicides can be used as a last option when other management options will not work. Handling chemicals should be done with caution and following instructions.  Uncontrolled use of agrochemicals are have adverse effects on the farmer's health, environment, and other beneficial organisms.

Note:

It is essential to regularly monitor or observe field crops for signs of nematode infestations. Based on this, appropriate measures should be used to manage them promptly.

Consulting with local agricultural extension services or university experts in your region can provide you with tailored advice and specific recommendations based on your farming conditions. Referring to authentic literature from reputed agencies is always recommended.