Gall nematode: methods of struggle

Gall nematode: methods of struggle

According to Taylor and Sasser (4), nematode reproduction can be used to measure root-knot nematode resistance, since reproductive ability on a given host is directly related to resistance. Oostenbrink’s (2) reproduction factor (R = final nematode population/initial nematode population) is used to measure the reproductive capacity of nematodes. Ab R-factor , 1 indicates an inefficient host (poor host); R-factor . 1 indicates an efficient host (good host). Gall index measures plant damage (host response), whereas reproduction factor measure nematode reproduction (nematode response). Sasser et al. (3) proposed using a resistance rating system based on gall index (GI) and reproduction factor (R). We used a modification of this system for slightly resistant (R > 1) and GI , 40), and resistant R 3 volume) pot. Pots contained sterilized sand and soil in a 1:1 ratio. Plants were grown from seed, each pot having one plant. Each plant was inoculated two weeks after planting with 5000 root-knot nematode eggs using the technique developed by Hussey and Barker (1). Plants were rated 8 weeks after inoculation (10 weeks after planting) first evaluating root-knot nematode damage using a gall index (0 to 100% of roots galled) and then measuring the numbers of eggs on roots. The number of eggs on the roots of each plant was determined using the technique for obtaining root-knot nematode eggs as described by Hussey and Barker (1).

Results. The number of juvenile nematodes in stage two (J2s) was not determined but R-factor and gall index should be sufficient to determine resistance to these nematodes. Meloidogyne incognita race 1 was the most pathogenic species used, with an R-factor and gall index mean of 5.3 and 73, respectively (Table 1). Furthermore, all but one cultigen had a susceptible rating when infected with M. incognita race 1 (Table 2). Five of six cultigens tested had R-factors greater than four (an efficient host has an R-factor > 1). Meloidogyne arenaria race 1 and M. javanica produced R-factors over all cultigens of 2.6 and 3.3 respectively (Table 1), indicating that most cultigens evaluated were efficient hosts for those nematodes.

All cultigens evaluated were resistant to M. hapla based on R-factor and Gall Index (Table 2). Resistance of C. sativus and C. metuliferus to M. hapla has previously been reported (5). Cucumis sativus ‘Sumter’ was the most susceptible cultigen tested with a mean R-factor of 10.4, indicating that ‘Sumter’ was a good host for root-knot nematode reproduction. Of the C. metuliferus accessions, only PI 482452 had an R-factor below one, indicating it was a poor host for root-knot nematode reproduction.

Of all root-knot nematodes evaluated, all plants were susceptible except PI 482452 (Table 2). Also, that accession was the only cultigen tested that was an inefficient host for M. incognita race 1. However, with respect to the root-knot nematodes evaluated, all C. metuliferus accessions tested were significantly different from C. sativus ‘Sumter’ except for M. hapla (Table 1). In this study, we found that R-factor can be used to determine degree of resistance in species of Cucumis, since gall indies and R-factors were somewhat comparable for each cultigen-nematode combination, which can be seen by the positive correlation (R = 0.68) between gall index and R-factor.

Table 1. Reproduction factors (Rf) and gall indices (Gall) for 6 cultigens of Cucumis spp. infected with 4 species of root-knot nematode z

Potato nematode and other types of parasite: characteristic features and photos

Cultivated plants grown as decorative or food in country houses and kitchen gardensare constantly being attacked by pests.

These are numerous animals, birds, insects and . parasites.

Nematodes — extensive group of parasites, causing significant damage to growing plants, settling on their leaves, stems and even roots.

In this article we will look at some types of nematodes capable of harm crop plants in your garden or garden.

What parasites look like what threat do they carry to plants and man, and most importantly — how to recognize this or that type of pest? Let’s try to deal with the characteristic features of each nematode, so that the fight against them will be the most successful.

Golden Potato Nematode

This type of parasite exclusively on plants from family solanaceous, able to affect the roots of tomatoes and potatoes. Potato nematode — what is it?

Golden Potato Nematode — Photo:

Sizes of Golden Nematode on Potatoes incredibly small and indistinguishable to the human eye. When viewed through a microscope, you can find that it is a worm up to 2 mm in length, having a rounded shape and a golden or brown color.

Infection of the plant roots occurs after the parasite is attached to it, which injects it into the root cells. special secretsplitting the entire contents of living cells. Then, the cells, thus softened, are absorbed by the nematode.

Potato nematode signs: the main signs of infection are, above all, bottom leaves — they turn yellow and dry. Almost immediately, the number of stalks near the bushes on potatoes is noticeably reduced — some of them wither, the rest do not grow to normal sizedying in the early stages. Tubers and flowers are also not formed, or are formed too small. All this is due to the violation of the flow of water and minerals through affected roots.

They can accidentally carried together with the remains of diseased plants, as well as with lumps of earth, tools, rainwater and wind. Golden potato nematode — is there a danger to humans?

To eradicate the nematode quite difficult, when grown in contaminated soil, it can cause serious damage to the crop, for example, to cause such diseases of potatoes as globoderosis (short stature of plants, deformed leaves, deformed root system with growths). However, for a man she absolutely harmless.

You will learn about the danger to the harvest of the golden potato nematode from the video:

There are several varieties of stem nematode, each species is able to parasitize only on one type of plant. Such nematodes are dangerous for onions, garlic and potatoes, as well as flower plants such as tulips, phloxes, carnations, begonias and some other plants.

The dimensions of the stem nematodes do not exceed 1.7 mm, the shape of the body is filiform. Stem nematode — photo:

Most often, infection occurs. through damaged root sites plants, less often through the skin. Once inside, nematodes begin to multiply rapidly, laying eggs.

Most faithful sign of infection in onions or garlic, is the condition of the cover. If the bulbs suddenly formed a bright white spot on the scales, which then swelled and became loose, then this is the site of active reproduction of the parasites.

If we consider the stems, we can notice characteristic thickenings and swellings, leaves and flowers are also crooked. In the most severe cases of infection, the plant dries and dies.

Understand that the reason is in the stem nematode, you can also on the color of the affected areas: they become pale in color, which eventually turns brown. This indicates destruction and dying off of stem cells.

Nematode stem cysts are less resistant than root cysts — they remain in the soil up to 5 years and are sensitive to high temperatures, so to prevent spread, infected plants are better to burn, although there are more benign methods.

Stem nematode causes ditilenhoz, which is manifested in the deformation of the leaves, as well as damage to the tubers, on which characteristic gray spots are formed. Despite the devastating effect of this parasite on plants, cases human infection has not been established. However, chemicals used in the fight against this pest are more dangerous.


it the smallest representatives among all plant nematodes. Sheet nematode has no color, and body length does not exceed 1 mm.

Sheet nematode — photo:

These parasites have the ability to very fast moving inside the plant and can tolerate viral diseases, such as the virus kurshavosti and the virus ring spot of tomato.

Nematodes parasitize on the leaves of many plants, but chrysanthemum, strawberries and tomatoes are particularly common.

The disease process is immediately reflected on the leaves in the form dry spots of irregular shapedisarrayed. Sometimes these spots have a yellow or brown color. Next comes the thinning and wilting of the leaves.

Unlike other species of nematodes, leaf chooses dry leaves as a shelter, less often soil. It can spread first of all due to careless contact with an infected plant, because up to 15 thousand microscopic specimens can live and develop on it. Nematode cysts are also found in the soil in winter, therefore important to work the land before landing.

Leaf nematode very dangerous for greenhouse and garden plants. It is capable of parasitizing not only in the leaves, but also affects the stems and even flowers, leading to the death of the plant organism. Unfortunately, to cure such a plant without harming oneself is almost impossible.

What is the harm to humans? AT human body leaf nematodes do not survive, however inadvertent use in large quantities can lead to easy poisoning due to the toxic metabolic products secreted by the parasite into the plant tissue.

Gallic root

Parasite on plant roots vegetable crops. Interestingly, the females of these nematodes lead an immovable lifestyle, whereas the males are larger and have activity to move.

The root nematode is a parasite. The length of the body of these parasites does not exceed 2 mm, in the early stages of development they have a whitish color, which with age grows pale and becomes transparent. That is why the fight against the gall nematode is considered one of the most difficult: independently, without the aid of a microscope, nematodes are difficult to distinguish from other root cells.

Gallic root nematode — photo:

The big danger is parasite penetration: the gall nematode does not need open wounds on the plant, it pierces with a sharp needle located in the oral opening, the cells, after which it penetrates into the tissues and settles into them. Plant exposed destructive toxins the parasite.

Shoots of plants are experiencing lack of water, and therefore begin to lag in growth and die.

When inspecting the root system, it is not necessary at the sight of blisters to immediately destroy the plant. Sometimes galls can appear from quite harmless symbiotic organisms, for example, nodule bacteria. It is best to give part of the root for examination.

Gallic nematode spreads first with soil, soil and sandIt is also possible direct infection through contact of root systems during transplantation.

Most plants die from the action of this parasite, but cabbage, garlic and cereals resistant to nematode. The gall nematode is capable of causing melodogenesis, accompanied by yellowing and wilting of the leaves, by slow growth of the plant.

There are some safe methods of struggle with the nematode, moreover, due to the narrow specialization of parasitism, the gall nematode does not penetrate higher than the roots, and therefore the probability of getting into the human body is minimal.

How to recognize the root nematode, you will learn by watching this video:

As you can see, even the smallest pest is able to inflict more damage to the plantthan ordinary birds and rodents, attacking the plant imperceptibly and slowly bringing it closer to death. Fight him very difficultHowever, based on the above symptoms and characteristics, you can try to limit its spread to other healthy plants.

Root-Knot Nematode

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Miscellaneous Pests

Root-knot nematodes ( 1147 )

Root-knot nematodes (Meloidogyne spp.) attack the roots of various trees, shrubs and herbaceous plants. Infested roots become distorted and develop rounded or irregular galls. These galls measure anything from 1 to 20 mm across and often coalesce, causing considerable distortion. The nematodes also exacerbate the deleterious effects of pathogenic bacteria and fungi. Root-knot nematodes are associated mainly with light soils but most damage is caused under glass, particularly in hot conditions where certain tropical and subtropical species, e.g. the Javanese root-knot nematode (Meloidogyne javanica), have become established. Pot plants such as Begonia, Coleus, Cyclamen, Gloxinia and various cacti may suffer considerable damage, severely affected plants appearing discoloured, lacking vigour and wilting under stress. Northern root-knot nematode (Meloidogyne hapla) is a widely distributed, polyphagous pest in northern Europe; it attacks many different kinds of plant, including various ornamentals. Root-knot nematodes invade host plants as second-stage juveniles; these settle down to feed in the young roots and usually reach maturity about 1–2 months later. Adult females are translucent-whitish, pear-shaped and about 0.5-1.0 mm long. They may be found within the galled tissue, often attached to a gelatinous sac that contains masses of eggs. In some cases development of the pest is parthenogenetic; in others, minute worm-like males mate with the females before eggs are laid. First-stage juveniles develop within the eggs, second-stage individuals eventually breaking free and either migrating inside the root or escaping into the soil to commence feeding elsewhere. These infective nematodes are capable of surviving in moist soil for about three months. In dry conditions they persist for no more than a few weeks.

1147 . Galls of northern root-knot nematode (Meloidogyne hapla).


Disease Cycle

Root knot nematodes may overwinter in the soil as eggs or juveniles. The juveniles can infect roots, and the eggs will hatch whenever soil becomes warm regardless of season. Both male and female larvae enter a small root of a susceptible plant and begin to feed on the vascular system. Root knot nematodes do not kill the tissue but cause the developing vascular tissue around the feeding area to enlarge and produce large, unvacuolated “giant cells.” The formation of giant cells is solely to benefit the nematode and provide the necessary nutrition for the nematode growth and subsequent production of large numbers of eggs. The root begins to swell in this area and continues to enlarge as the nematodes complete their larval stages and become adults. Mating occurs shortly after they reach the adult stage and the males then leave the root. After fertilization the female’s body becomes progressively enlarged with developing eggs, causing the further enlargement of the root. Large amounts of the water and nutrients absorbed by the feeder roots and moving in the vascular system toward the aboveground parts of the plants are being channeled into the root knot nematodes throughout their development. When the eggs are mature the female causes a rupture in the side of the root next to her body and releases the eggs outside the root into the soil to begin a new disease cycle.

A few root knot nematodes will have little effect on a healthy plant, especially a woody plant with a large root system, but large numbers of galled roots can affect the health of a plant regardless of size. However, owing to their developing root systems young plants are more susceptible to serious injury by root knot nematodes than older plants.

The mobility of root knot and other nematodes is small. On their own they can infect only plants very close to the location of their birth. They can, however, be moved great distances in soil and in infected plants, and can also be transported locally in surface water especially used for irrigation. Once established in a field, nursery, or around a shade tree they are usually able to persist and often to increase their population size. In the absence of a susceptible woody plant they may remain established on weeds or crop plants for an indefinite period.

Vegetable Production Root-Knot Nematodes

Root-knot nematodes are among major pests of economic importance in tomato production in Southern Africa. They induce galls swellings of about 1–2.5 cm in diameter on plant roots and can cause yield losses of about 30% by direct infestation, and indirect losses due to predisposition or breakdown of resistance to other root diseases, such as bacterial wilt can be significant. Damage in the field usually appears as irregular patches and is frequently associated with light-textured soils. Nematode infestation is observed when an area in the cultivated field has part of the crop clearly lagging behind in growth, the plants are lighter in color, and their leaves abnormally shaped without signs of a mosaic pattern. It usually begins in a small, limited part of the cultivated area, and spreads slowly throughout the field.

Three common types of root-knot nematodes affect tomato, including Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne arenaria. The root system of the affected plants is stunted leading to a poorly growing crop, and such plants are often prone to soilborne fungal and bacterial diseases. Their infestation and transmission occur via infected plant material, agricultural tools, rain and irrigation water, strong winds (which carry infested soil particles), and contaminated soil carried on shoes or animal feet. Nematodes will survive in soil as long as it stays moist.

Tomato roots infested by Meloidogyne incognita root-knot nematodes.

Courtesy Scot Nelson at University of Hawaii.

Introduction to Nematode Control

There are thousands of varieties of nematodes, some beneficial and some harmful. Nematodes have adapted to just about every ecosystem on the planet—they live at high and low elevations, in polar and tropical regions, in fresh water, seawater and on land. In the world of soil-based agriculture, most harmful nematodes fall into the sting, lance or gall types. According to the APS (American Phytopathological Society), nematodes account for an estimated 14% of all worldwide plant losses or nearly $100 billion dollars annually!

Root-knot or gall nematodes are the worst culprits of the group. These nematodes form a gall or bump on the root of the plant and live inside it. Although nematodes are microscopic, the galls they form are often quite large. They damage roots so much that they can no longer provide proper nourishment to the plants. It’s really easy to see the damage that’s caused by the root-knot nematode, and it costs global agriculture a lot of money because it’s very difficult to control.

Nematode Control Methods

Methods of nematode control fall into three broad categories: Cultural practices, chemical control and biological control.

Cultural Methods of Nematode Control

Rotating crops is a good way to control nematodes. You may have a crop that’s highly susceptible to nematodes, and then you rotate that field to other crops that are not susceptible. For example, if you have a field that you’ve been growing tomatoes in for 2-3 years and you rotate that to pasture grasses for 2-3 years, you will systematically and culturally control the nematodes.

The type of root-knot nematodes that damage tomatoes does not colonize the roots of grasses. When you transfer the field to grasses, you’re basically creating an environment where the root-knot nematode no longer has a host. If you remove the host, the population will decrease in the field. This is the opposite of monocropping, where you grow the same crop over and over again, allowing the population of nematodes to become progressively more problematic year after year. Crop rotation is a cultural way of controlling nematodes, and it can work quite well. There are even cover crops which produce chemicals that are toxic to nematodes. However, if you have several types of nematodes in your soil, finding a crop rotation that will starve out all of them can be a bit tricky.

Mechanical methods, such as repeated tilling of fallow soil, may also be useful, but may be difficult to implement on a large scale.

Chemical Control of Nematodes

Chemical controls include fumigants and nervous system toxins. Fumigants have to penetrate a large volume of soil to be effective, and some of them volatize quickly. Large amounts of chemicals are often used, leading to increased risk and expense. Methyl bromide, a broad-spectrum pesticide often used for nematode control, is being phased out under the Clean Air Act. This has led to a search for alternatives.

Nervous system toxins can also provide effective nematode control. Because they are not toxic to plants, these chemicals (carbamates and organophosphates) can be applied after plants are growing and nematode damage is visible. However, since human beings also have nervous systems, any chemical treatments that target the nematode nervous system are a potential danger to humans. These chemicals are extremely toxic to humans and other nontarget organisms, but there are alternatives.

Biochemical and Biological Nematode Control

Biochemical and biological controls can be used in conjunction with other controls or on their own. By naturally repelling nematodes and improving plant health, these methods may decrease dependence on chemical controls.

SoilTech Corp has two products that can be used for nematode control: Armorex and Nemastop.

Armorex is a full spectrum soil treatment that can help control soil borne fungi and insects in the soil as well as parasitic nematodes. Made from natural oils, it kills on contact and maintains a repellent action against many soil insects, nematodes and fungi. Armorex is exempt from EPA residue tolerance requirements and there are no re-entry restrictions. Sometimes used in place of methyl bromide, Armorex can be used as a soil pretreatment or during the growing season.

Nemastop is used post-planting to control nematodes and fungi. Composed of organic extracts blended with fatty acids, Nemastop can be used on turfgrass, ornamentals and food crops. It’s non-phytotoxic and also carries no residue tolerance.

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