Dr. Hamood M. Saleh

Plant protection

    Nematodes are cylindrical, worm-shaped worms that live in salt and fresh water, or at least their body is covered by a thin membrane of water in the soil in order to be alive and active. The plant parasitic nematodes are no more than 5 mm long and no more than 100 microns in width . They constitute about 10% of the general total of nematode species, but no plant may survive the possibility of being infected with one or more species of this group. Plant nematodes live in multiple geographical regions of the world and in different plant environments. All types of these nematodes are considered obligate parasites, and they either parasitize the root tissues externally or internally, or internally parasitize the vegetative system. Plant nematodes represent one of the most important agricultural pests that share our food and greatly affect our agricultural economy, as the cultivation of economic crops on large areas in many countries of the world, being infected with nematodes, constitute heavy losses in terms of the amount of production and the national income of these countries. Sometimes farmers notice in their fields that plants have green leaves that tend to yellow, plants that are stunted, and small fruits, and the plants do not have any signs of fungal or insect infections, knowing that it follows a very orderly and accurate irrigation and fertilization program. Farmers think about several reasons, and they do not know that this lies in infecting the roots of plant with nematodes (the hidden enemy). Usually, all types of plant pathogenic nematodes spend a large part of their life in the soil and feed on roots and stems growing under the surface of the soil due to the presence of their preferred food, which they are attracted to by the attractive substances secreted by the host in the soil, especially in the root area. The feeding process damages the plant's root system and reduces the plant's ability to absorb water and nutrients. The nematode feeding process causes the plant cells to react either by forming swelling, tumors, root lessions , seed galls , root galls or yellowing of the plant. The effect of nematodes on their different hosts is not limited to a direct pathogenic effect, but to a large extent exceeds the harmful and important effect that occurs as a result of the cooperation and interaction of nematodes with other microorganisms, especially those that live in the soil. Therefore, such interaction results in disease complexes that cause heavy losses. It was also found that infection with nematodes  leads to loss of resistance to other diseases, as the infection leads to anatomical and physiological changes in the affected plant, and it is believed that physiological changes are responsible for the loss of resistance in many varieties to some diseases. It was observed that Infection of leguminous plants with root-knot nematodes led to inhibition of the formation of beneficial bacterial nodules, thus inhibiting atmospheric nitrogen fixation. Infection with root nematodes may also cause damage to the mycorrhizal fungi that are beneficial to the roots and disruption of their work in protecting the roots from other diseases. Based on the foregoing, farmers must be assisted in taking the necessary decisions and measures for the control process by one of the used methods, which is either by using nematode pesticides or agricultural methods such as resistant varieties or fallowing or using solar energy to sterilize agricultural soil or using biological control, in order to limit the spread of nematodes and not to waste the agricultural producer provides additional money, which reduces the profit margin or increases the cost of agricultural production.