Nematodes are multicellular organisms that are elongated cylindrical “worms” with reduced diameters at both ends, generally microscopic (about 0.5 mm long), and they possess most of the physiological systems of higher organisms, with the exception of the respiratory and circulatory systems. These organisms invade the stems, leaves and seeds, roots, bulbs, tubers and corms of plants.The genus Meloidogynespp, known as the most economically important genus in tomatoes, these nematodes cause severe damage and yield losses to a large number of cultivated plants, especially vegetable crops in tropical and subtropical regions. This paper presents the results of a work carried out from March to June 2015 in a tomato greenhouse located in San Pedro Nopala, Oaxaca, where excellent results were achieved in controlling nematodes using nematicides based on plant extracts, fertilizers, biostimulants and the addition of microorganisms to the soil.
Biological Cycle of Nematodes
Nematodes have six developmental stages: eggs, four juvenile stages, and adults. Eggs are generally deposited in the soil or within plant tissues at different developmental stages. In some species, they are protected by a gelatinous layer. When an egg is fertilized, it undergoes a series of division stages until it reaches the juvenile stage. In most species that affect the second juvenile stage of the plant, it emerges from the egg, moves through the soil, and penetrates and invades plant tissues. This stage, which is usually infectious, is, in most species, the stage of resistance to environmental conditions (Roman and Acosta, 1984).
Symptoms
It spears as wilting, shriveling, dwarfing, lack of vigor in the aerial parts of the plant due to lack of water and nutrients, as the nematodes impede their passage; in the roots of the plant, there are nodules with roots like potatoes, peeling, deformation and necrosis of the root cortex, overgrowth of the roots (witches’ broom), shrinkage of the root tips or the ends of the roots and, in some cases, stunting of the root system. The severity of the damage depends on the variety (some tomato varieties are resistant or highly tolerant to nematodes), the nematode species, the age of the plant and the prevailing environmental conditions.
How Can We Treat Nematodes?
There are a good number of nematicides at your disposal. Among them there are many for organic cultivation, such as the spores, which in addition to preventing can help eliminate an infection. There are also specific products, based on chemical substances capable of eradicating the plague. Within these we find the active ingredient
paecilomyces lilacinus, which serve to prevent the pest from continuing to grow, and the purely nematicides.
This classification also depends on the type of nematode that is attacking the citrus. Endoparasitic nematodes, that is, nematodes that parasitize inside plant tissues, are much more difficult to treat, and a nematicide may only have nematostatic properties since it cannot kill all the animals.
Sometimes, despite treatments, the crop will not react well, or in time, to stop the further damage of nematode infection due to their various life cycles: it is always easier to treat nematodes at the top of the crop. plant than those that act on the root and, in both cases, external parasites are always easier than internal parasites. Therefore, it is better to try to prevent than to treat.
Results and Conclusions
The results were excellent and very satisfactory since after having used many highly toxic agrochemicals and in an excessive way, without obtaining good results, the treatment based on plant extracts, biostimulants and beneficial microorganisms allowed the development of the tomato crop in a normal way without decrease yield, making it an excellent option for nematode control.
