Nematodes are tiny invertebrate animals, their length ranges between 0.4-4 mm and width between 20-250 microns, and they are filamentous in shape.
They are also called snake worms or nematodes, and they live in the soil.
The females take different shapes and the shape of the females differs from that of the males, as the males take the filamentous form, while the females take a lemon or pear, as in the root knot nematode or the vesicle nematode, or they take a kidney form such as the renal nematode and citrus nematode.
Nematodes also infect many important economic crops, whether they are horticultural crops, field crops or ornamental plants.
Nematode infections in horticultural crops:
Nematodes infect the following fruit crops:
Citrus, grapes, peaches, almonds, olives, bananas, apples, figs and plums.
Nematoda infect the following vegetable crops.
It infects tomatoes, peppers, cucumbers, potatoes, eggplant, beans, cantaloupes, melons, strawberries, cabbage, okra, potatoes, zucchini and carrots.
Nematode infections in field crops:
Nematodes infect the following field crops:
Peanuts, alfalfa, peas, soybeans, sugar cane, cowpeas, onions, corn, wheat, cotton, sugar beet, sunflower (sunflower) also infect rice.
Nematode infections in ornamental plants are as follows:
Nematodes from ornamental plants infect carnations, jasmine, gladiolas and roses, as well as many different weeds.
Parasitic nematodes also spread in many types of soil and at different temperatures and cause great damage to crops, sometimes reaching complete loss of the crop.
And some types of nematodes have a large number of (non-specialized) hosts such as root-knot nematodes and renal nematodes.
Some types of nematodes have a limited family specialization to a large extent, which are specialized nematodes such as vesicles nematodes and bulbs nematodes.
There are also some types of nematodes, in addition to their direct harmful effect on plants, they help infect plants with other diseases, such as the relationship of nematodes and wilt fungus in tomatoes.
As well as the relationship of root knot nematodes with root rot fungi in fig varieties, there is also a strong relationship between nematodes with fusarium wilt on different banana varieties.
As well as the relationship between some types of nematodes and some viral diseases such as scaly nematodes and TRV virus (corky spot) in potatoes, as well as xiphoid nematodes and some viral diseases, which is a biological relationship.
Some types of nematodes spread in light lands or sandy lands, such as root-knot nematodes and citrus nematodes – ulcer nematodes – and some types of nematodes spread in heavy lands such as renal nematodes.
How Nematoda spread and different methods of spread.
1- Through infected seeds, as in grapes, citrus fruits, bananas and tomatoes.
2- Through contaminated soil attached to seedlings, agricultural machinery or farm animals.
3- Through contaminated soil and transferred from infected places, or by adding organic fertilizer (country) contaminated with nematodes.
4- Through irrigation water contaminated with nematodes or through weeds spread in different crops.
Symptoms of Nematoda infection.
Nematode diseases are like viral, bacterial and fungal diseases in that they cause harmful physiological activity resulting from a reason that pushes the infected plant to a state of abnormal cellular activity that appears in the form of specific symptoms called nematode pathological symptoms.
Symptoms of nematode infection appear in the following cases.
First the external symptoms.
External symptoms are symptoms that appear to the eye, such as root knots, spotting, stunting, wilting, ulceration, rotting or death of the limbs, and all of these symptoms are symptoms that appear and are seen on infected plants.
Second: internal symptoms.
Internal symptoms appear after dissecting infected plants and examining them under a microscope, such as cell enlargement and an increase in the number of cells that result in swellings or knots or tissue death that results in ulcers or mold.
Symptoms of nematodes according to the nature of their nutrition in plants.
1- Nematodes are parasitic on the vegetative system (leaves, stems, buds and flowers) as in:
* Nematoda market and bulbs.
* Nematoda seeds and leaves.
* Nematoda buds and leaves.
2- Nematoda are parasitic on the root system, as in:
* Ectoparasitizing nematodes: they externally parasitize the root system without entering the host plant tissue, such as dwarf nematodes, xiphoid nematodes, root-shelled nematodes, spiral nematodes, and needle nematodes.
* Endoparasitic nematodes:
Where nematodes parasitize inside the roots and different parts of the host after penetration, and examples are root knot nematodes, vesicles nematodes, ulcer nematodes, and borer nematodes.
* Semi-internal parasitizing nematodes:
It is a nematode that feeds on the roots of the host after a large part of the nematode introduction penetrates the tissue of the host, such as citrus nematodes and renal nematodes.
Classification of nematodes according to the host range.
1- Specialized nematodes: This type of nematode includes a limited number of hosts such as seed nematodes, leaf-knot nematodes, cyst nematodes, market nematodes, and bulbs.
2- Non-specialized nematodes: This type of parasitic nematodes includes an unlimited number of hosts such as root-knot nematodes, renal nematodes, ulcer nematodes, xiphoid nematodes, and spiral nematodes.
Methods of chemical control of nematodes:
Chemical control is the use of pesticides to control and eliminate nematodes, as follows:
First, for the fruit:
1 – For citrus nematodes (
slow decline disease of citrus fruits):
* Modern planting of infected citrus seedlings uses 10% nemacor pesticide at a rate of 35 kg / feddan, using scattering on the surface of the soil around the affected trees.
Or Vidite pesticide 10% at a rate of 25 kg / feddan, used scattered around the affected trees.
* Citrus fruit trees infected with nematodes:
Timec pesticide 15% is used at a rate of 17 kg / feddan, using scattering around trees.
Or Fordan pesticide 10% at a rate of 40 kg / acre spread around the affected trees.
Or Vidite pesticide 24% at a rate of 8 liters / acre (4 + 4) / feddan, and it is repeated after 3 weeks.
2- For bananas to resist root canker nematodes, as well as spiral nematodes, the following pesticides are used:
* 10% granular Nimacor pesticide at a rate of 30 kg / acre or the use of a 10% granular Mocap pesticide at a rate of 30 kg / acre.
3- Grapes to resist root knot nematodes and deterioration by using the following pesticides:
* Vidite liquid 24% pesticide at a rate of 10 liters / acre
(5 + 5) and repeat a month after the previous spray.
4 – Peaches, plums, apricots, almonds and olives to combat root-sitting nematodes. The following pesticides are used:
* Vidite liquid 24% pesticide at a rate of 4 liters / acre twice, to be repeated after 3 weeks.
5- Vegetable crops infected with nematodes are controlled using the following pesticides:
* In tomatoes in the nursery, Nimacor 10% pesticide is used at a rate of 20 kg / acre or Vidate 10% at a rate of 20 kg / acre
* In potatoes infected with root-knot nematodes, 10% mocap pesticide is used at a rate of 30 kg / feddan, or 10% carbofuran is used at a rate of 13 kg / feddan.
* In eggplant to resist root knot disease and ulceration, Fordan 10% pesticide is used at a rate of 13 kg / feddan.
* In strawberries to combat root-knot nematodes, canker nematodes and leaf nematodes, Fidet liquid 24% is used at a rate of 3 liters/acre spray/600 liters of water.