Brodie: Golden Nematode Control

Golden potato nematode, stem — causes and methods of control

Golden Nematode:
A Success Story for Biological Control

Bill Burl Brodie
Nematology & Plant Pathology
Cornell University
Ithaca, NY 14853

(prepared from the videotaped presentation*)

For the purpose of this conference and this presentation, I hope that you biological control specialists will allow me to include in your definition of biocontrol the use of host plant resistance. In any case, this strategy is a biologically-based means of control.

We have used host plant resistance to control a very important disease of potato, the golden nematode. This is a quarantined pest that occurs in the U.S. only in the state of New York. So, when we talk about the goal of golden nematode control, it’s not about yields, it’s not about growing healthy plants, it’s about reducing the population of a plant pest to a level where it can’t spread.

Dr. Bob Plaisted, a plant breeder at Cornell, Dr. Steve Slack, a plant pathologist at Cornell, Dr. Don Halseth who is a Cornell potato specialist, and I developed and promoted the use of the resistant potato varieties used in this program.

For many years, golden nematode was controlled with the soil fumigants, D-D or Telone, which were applied at 90 gallons/acre. Any chemical applied to the soil at that rate will eventually get into the groundwater, and this occurred in New York.

To prevent this contamination, an effort was made to find a biologically based method to control the golden nematode. To accomplish this type of control, the following aspects of the biology of the potato cyst nematodes (PCN) were considered:

  • The PCN is an obligate parasite.
  • The PCN ‘s host range is limited to the Solanaceae.
  • PCN can survive 20-30 years in soil without its host.
  • PCN hatches primarily in response to potato root exudates.
  • PCN requires males for reproduction.
  • One generation is produced per year.

A cyst contains 300-400 eggs, each capable of hatching when stimulated to do so by potato root exudates. If no food is present when the nematode hatches, it will die within a couple of weeks. Thus, what we once thought was the nematode’s strength can also be its weakness, because the nematode cannot distinguish between resistant and susceptible plants: they hatch equally in the presence of both types of potatoes.

The nematodes hatch and penetrate the roots of the potato plant. If it’s a susceptible plant, the nematode will penetrate the root and establish a feeding site (syncitium) involving giant cells and will feed on those giant cells until it produces another generation.

However, with a resistant plant, the nematode hatches and, once inside the plant, a reaction which we haven’t yet identified occurs and juveniles are stimulated to exit the roots.

We also found that if nematodes emerge from a susceptible plant they will readily repenetrate either a susceptible or a resistant plant. But if they emerge from a resistant plant, they seem to have lost their taste for potatoes and very few will repenetrate another potato plant, either susceptible or resistant. (Table 1) This is one characteristic of reducing the nematode population.

Table 1 — Assessment of Repenetration
Emerged from Katahdin Rose
Katahdin (susceptible) 10.714a 15.567a
Rose (resistant) 2.561b 2.730b

Another characteristic of resistant plants is that those nematodes that decide to stay and establish a feeding site find that the cells exhibit a hypersensitive reaction: the cells die that immediately surround the nematode in the plant root and because the nematodes cannot feed on dead cells, they die from lack of food.

Finally, those that do survive, and they are few — not more than 5 per plant — have a diminished capacity for reproduction. On a susceptible plant, there are over 200 eggs produced per cyst, while cysts that are produced on a resistant plant have about 40 (Table 2) . In addition, the juveniles from eggs produced on a resistant plant have a very low infectivity.

Table 2 — Cyst Size Comparison
cyst size
Host #45 #60
Katahdin (susceptible) 229.7 76.2
Rose (resistant) 39.7* 0.0**
*Significantly different at P = 0.0001
**All data values zero; no analysis performed

This scenario for controlling golden nematode with host-resistant plants worked well in the laboratory and in greenhouse pots, but would it work in the fields?

In potato fields, there are hills, where the plants are, and furrows between the plants, where there are no roots. The hills contain about 70% of the soil volume and the furrows contain about 30%. We believed that we could control the nematodes in the hills, but could we control them in the furrows? We need to control all the nematodes because this is a quarantined pest, and in order to effectively manage the population we cannot allow any nematodes to survive.

What we found is this: In the hills where the susceptible variety had grown, there was an increase in the nematode population, and when the resistant variety was grown, there was a population decrease. In the furrows, there was a population decrease when either a susceptible or resistant variety was grown.

We discovered that the hatch-inducing chemical produced by potato roots moves through the soil to the eggs in the furrows, but because the nematodes don’t move far enough through the soil, they can’t get to the roots and they die. Thus, even with the susceptible plants, there is poor reproduction and the population declines in the furrows. In lab tests, we found that the chemical responsible for hatch stimulation moves 70 cm laterally and 50 cm deep from it point source of production through the soil in sufficient strength to stimulate nematodes to hatch.

From previous research we knew we needed to reduce the number of eggs to less than 0.2 eggs/cc of soil so that the nematodes would be at such a low density they would not spread. We developed a cropping system that alternated yearly plantings of resistant and susceptible potato varieties and nonhost crops that would keep the nematode population low.

Note that the initial density is

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Nematodes in Agriculture; Control Methods

Nematodes in Agriculture

Today, we learn about plant nematodes in agriculture and their control methods.

Plant Parasitic Nematodes in Agriculture:

Many Farmers are nowadays facing heavy crop losses in Fruit Crops and Vegetable crops due to various unpredictable diseases caused by Nematodes. A typical example is Guava wilt caused by a nematode Guava wilt Nematode Meloidogyneenterlobii which is infested from foreign countries and it is infested into south India due to poor domestic as well as international plant quarantine measures. The Guava Wilt Nematode has caused heavy crop losses due to an infestation of the Nematode. There are also some examples like Golden Nematode on Potato etc. Therefore, we have come with this information on Nematodes and How to control Nematodes in Fruit and Vegetable Crops.

What are Nematodes:

Nematodes are triploblastic, bilaterally symmetrical, unsegmented, with 4 hypodermal chords, triradiate oesophagus, pseudoceolomicinvertebrates, with nerve ring circum oesophageal, however lacking respiratory and circulatory systems. Simply Nematodes are Worms that are a thread like or resembles thread. They are also known as eelworms or roundworms denoting their shape. The word Nematodes is derived from the Greek language. Nematodes are known as Nema as their nickname in the US.

How Nematodes cause disease to Plants:

Nematodes that cause diseases to plants are known as Plant-parasitic Nematodes. However, there also exist free-living nematodes that are not at all harmful to plants. In this post, we will let you know how to identify plant-parasitic nematodes from free-living nematodes. Plant parasitic nematodes are provided with special organs known as stylets that help in piercing the plant cells and penetrating into the plant cells. There are also Nematodes that cause diseases to humans and animals like intestinal roundworm in human intestine that causes anemia. The scientific name of this human parasitic nematode is Ascarislumbricoides. There also exist more human and animal pathogenic nematodes.

Where do Nematodes live at: Most of the plant parasitic Nematodes live in the Rhizosphere of agriculture crops. However, there also exists foliar nematodes that feed on the foliage of agricultural economic important crops.

Economic Importance of Nematodes in Agriculture:

  • Being obligate and plant parasitic, there has been a record of 1800 species of Plant Parasitic Nematodes.
  • Annually, Nematodes cause 12% to 13% of agriculture losses in the world. Prof. J.N. Sasser has led the first way to authenticate and estimate the economic losses caused by plant parasitic nematodes.
  • Nematodes had caused 11% annual losses in vegetable crops in the US which is estimated to an economic loss of $267 mil/year.
  • In India, Rajasthan has faced an annual loss of Rs. 32 mil and Rs. 25 mil in wheat and Barley crops due to the infestation of Cereal Cyst Nematode, Heteroderaavenae.
  • In Northern regions, Seed Gall Nematode Anguinatritici in combination with bacteria caused heavy losses up to Rs. 70 mil in the Wheat crop.
  • In Karnataka, Lesion Nematodes, Pratylenchus coffee had infested around 1k ha of coffee estates.
  • Besides, these there are numerous crops infested with this plant-parasitic nematodes. Among which, vegetables are nowadays highly susceptible to plant parasitic nematodes.
  • Most of the farmers are unable to diagnose the disease caused by the Nematodes as they live in the rhizosphere and typical symptoms are only visible on the hosts. However, fewer symptoms are seen on the foliage of agriculture crops.

Favorable conditions for Nematodes in Agriculture crops:

  • The growth and development of Plant-parasitic Nematodes are favored by various environmental conditions especially the rhizosphere ecosystem play an important role.
  • Plant Parasitic Nematodes as they feed on the roots their presence depends on the deeper root system. However, most of them are confined up to a depth of 25 to 30 cm below the soil.
  • Soil temperature: 15 – 30°C. Also survive at 5 and 40°C.
  • Soil humidity or soil moisture: 40% to 60%.
  • Soil texture: Light soils are most favorable.
  • Osmotic pressure: 10 atm.
  • Soil pH: Between 4 – 8 pH.
  • Soil microbes: Sometimes, Nematode infestation may lead to the incidence of various plant pathogens as plant are susceptible to diseases after infestation by plant parasitic nematodes.

Classification of Plant Parasitic Nematodes:

Plant Parasitic Nematodes are mainly classified into two type’s viz., phytonematodes above ground parts and PhtoNematodes below ground parts

Plant Parasitic Nematodes above ground parts:

These are the Plant pArasitic Nematodes that parasites on above ground level parts that is a foliar region or foliage i.e., leaves, stems and flowers, and seeds.

Gall-forming Nematodes: Wheat Seed Gall Nematode – Anguinatritici

Leaf gall Nematode – Anguinabalsamophila

Non – gall forming Nematodes: Stem Nematode – Ditylnechusdipsaci and Ditylenchusangustus

Foliar Nematode – Aphelenchoidesritzemabozi and Aphelenchoidesfragariae

Plant Parasitic Nematodes below ground parts:

These rhizosphere Nematodes constitute the Nematodes that causes major economic losses in agriculture and horticultural crops.


Migratory Ectoparasites:

Sting Nematode – Belonolaimus sp.

Dagger Nematode – Xiphenema sp.

Needle Nematode – Longidorus sp.

Stubby Root Nematodes – Trichodorus sp.

Sedentary Ectoparasites:

Sheath Nematode – Hemicycliophoraareneria

Sessile Nematode – Cacoparuspestis

Semi Endoparasites

Migratory Semi Endoparasites:

Spiral Nematode – Helicotylenchussp.

Lance Nematode – Haplolaimus sp.

Stunt Nematodes – Tylenchorynchus sp.

Sedentary Semi Endoparasites:

Citrus Nematode – Tylenchulussemipenetrans

Reniform Nematode – Rotylenchusreniformis


Migratory Endoparasites:

Lesion Nematodes – Pratylenchus sp.

Rice root Nematode – Hirschmaniella sp.

Burrowing Nematode – Radopholussimilis


Root knot Nematode –Medoidogyne sp.

Cyst Nematode – Globodera sp. and Heterdera sp.

How to control Plant Parasitic Nematodes in Fruits and Vegetable Crops:

Management of Plant Parasitic Nematodes is difficult but easy if we go for some mandate precautions or Good Agriculture Practices(GAP) in our farm. As Plant Parasitic Nematodes can survive and adapt to vast environmental conditions, they are somehow difficult to control them.

Cultural Methods for Nematode control
  • Crop Rotation
  • Fallowing
  • Flooding
  • Healthy plant material propagation in fruit crops and whenever necessary
  • Rogueing
  • Proper application of organic amendments in the field
  • Cultivation of Trap crops or antagonistic crops
  • Sowing time (either early or late)
  • Soil solarisation
Physical Methods of Nematode Management

Nematodes cant thrive temperature above 40°C. Therefore, the seedling material is done with Hot water treatment at the rate of seed or seedling dip in 54 to 55°C water for about 10 to 15 min. However, there also exist some other methods like irradiation, osmotic pressure and ultrasonic treatments which are rarely used in Nematode management.

Chemical management of Phyto Nematodes

Fumigants spray:

  • DD mixture
  • EDB ( Ethylene DiBromide)
  • MBr (Methyl Bromide)
  • Toluene 1,3 dichloro propene
  • Nemadgon or DBCP – DibromoDichloro Propane (Banned)

Non Fumigants spraying:

  • Fensulfothion
  • Phenamiphos
  • Phorate
  • Aldicarb
  • Carbofuran
  • Metham sodium
  • Oxamyl

Biological control of Plant Parasitic Nematodes:

There are some pathogenic fungi like Paecelomyceslilacinus and a bacteria Pastureiapenetrans that kills or arrests the growth of plant parasitic Nematodes.

Root Knot Nematode: How To Wipe Out These Plant Parasites

I talk a lot about the root knot nematode in some of the pieces I do, and that’s because this microscopic parasite can do a lot of damage to your plants. It’s not easy to determine if you’re battling against them, and yet your plant will suffer its effects.

So let’s discuss what these itty bitty parasites are, and what they actually do. We’ll go over methods to try to eliminate them from your yard, and talk about the differences between good nematodes and bad ones.

By the time we’re done, you should know the basics of how to deal with this particular batch of parasites to the best of your ability, and how to keep them away from your prized plants!

Listen to this post on the Epic Gardening Podcast

Good Products To Fight Root Knot Nematodes:

Root Knot Nematode Overview

Wheat showing signs of root knot nematode galls. Source: CIMMYT

Common Name(s) root knot nematode, root-knot nematode, northern root-knot nematode, southern root-knot nematode, cotton root-knot nematode, peanut root knot nematode, British root-knot nematode, tea root-knot nematode, mature tea nematode, Indian root-knot nematode, coffee root-knot nematode, barley root-knot nematode, cereal root-knot nematode, African cotton root-knot nematode, African cotton root nematode, Thames’ root-knot nematode and other names
Scientific Name(s) Meloidogyne spp. including Meloidogyne javanica, Meloidogyne arenaria, Meloidogyne incognita, Meloidogyne hapla, Meloidogyne enterolobii, Meloidogyne acronea, Meloidogyne artiellia, Meloidogyne brevicauda, Meloidogyne chitwoodi, Meloidogyne exigua, Meloidogyne fruglia, Meloidogyne gajuscus, Meloidogyne naasi, Meloidogyne partityla, Meloidogyne thamesi
Family Meloidogynidae
Origin Worldwide
Plants Affected Alfalfa, African daisies, African violet, almond, apricot, avocado, azalea, banana, barley, bean, blackberry, butterfly flower, cantaloupe, carrot, capsicum, chickpea, cineraria, citrus, coffee, corn, cotton, cucumber, date palm, eggplant, grapes, hemp, hibiscus, hops, hydrangea, Jerusalem cherry, lentil, lettuce, lilac, nectarine, okra, olive, onion, papaya, pea, peach, peanut, pear, pecan, pepper, pigeonpea, pineapple, plantain, plum, potato, primula, pumpkin, raspberry, red clover, rose, soybean, squash, strawberry, sunflower, sweet potato, tea, tobacco, tomato, walnut, watermelon, many wild grasses/shrubs/trees/weeds. Thousands of species of plants may be impacted by root knot nematodes.
Common Remedies Geraniol or quillaja saponaria compounds, azdirachtin, neem seed meal, crab meal, oyster shell flour, juglone (from black walnut leaves/hulls), soil solarization, addition of beneficial nematodes, planting of marigolds or sudangrass as cover crops.

All About Root Knot Nematodes

From their name, it’s pretty easy to guess that these affect the roots of plants. But where do they come from, and what exactly are they?

What Are Nematodes?

A nematode is actually a form of roundworm. The category of roundworms is incredibly wide, covering at least 25,000 different species. Some of these species are beneficial to us, some are harmful.

From an agricultural perspective, there’s really two forms of nematode which are important to be aware of: predatory or parasitic.

Predatory nematodes are types which seek out and attack an assortment of other garden pests like cutworms or squash vine borers. I often refer to these as beneficial nematodes, as they help keep our gardens pest-free. These are great to have around!

Parasitic nematodes, on the other hand, are not so great. Often invisible to the naked eye, these will attack living plant matter and consume it. They can cause the plant to focus its attention on healing that damage rather than healthy growth.

Root knot nematodes, the Meloidogyne species, fall into the parasitic category. They can cause our plants to inexplicably yellow, develop stunted growth, or look weak. Their chewing on the root systems of plants can allow other plant diseases to take hold as well.

Root Knot Nematode Life Cycle

The life cycle of these particular nematodes can be quite complex, but it breaks down into a few phases. There is an embryonic stage, four juvenile stages, and an adult form.

An adult root knot nematode will create a gelatinous mass on the root system of a plant and lay its eggs into it. Up to a thousand eggs can be laid by one adult. During this embryonic stage, the nematode will go from embryo completely through the first juvenile phase.

Once the embryo has become a first-stage juvenile, it will begin to eat the egg it is encapsulated in. By the time it has consumed its egg and some of the gelatin around it to encounter soil, it has become a second stage juvenile.

This is when the root knot nematode begins to pose a danger to the plants. Second-stage juveniles will eat their way into the root. Their chewing and migration through the root causes root galls, which are bulbous masses that the plant forms while trying to heal its root system.

In time, the second stage juvenile will take up residence inside one of these galls. It will undergo its third and fourth juvenile stages inside the root knot or gall, moulting and developing until it emerges as an adult and begins the cycle anew.

Common Habitats Of Root Knot Nematodes

Soil-dwellers, root knot nematodes can be difficult to identify. After all, you usually cannot see them with the naked eye, and they aren’t above ground. In fact, they can often do so little damage to larger plants such as trees that they are not recognized as being there at all.

However, they do in fact attack thousands of plant species ranging from food crops to trees, shrubs, and ornamental plants. There are estimated to be more than 90 different species, and while some are preferential to particular plant types, many are opportunistic.

They can be found around plant/tree roots in the soil, or inside the roots themselves. Depending on the phase of the life cycle, they may have caused the plant to create galls which they may inhabit.

What Do Root Knot Nematodes Eat?

It’s estimated that most nematode damage to food crops is done by the Meloidogyne species.

They only eat living plant material, and tend to only attack plant roots rather than to go after any above-ground plant matter. The range is very wide, comprising thousands upon thousands of plant species worldwide.

Four particular species of root knot nematode are at extremely high levels internationally and cause the majority of agricultural damage. Another seven species cause significant crop damage in their particular regions of the world, but have not reached global proportions.

The remainder of the root knot nematodes tend to feed mostly on the roots of grass, weeds, and wild plants or trees. These are still damaging to their targets, but are considered less significant as they do not directly attack human food supplies.

The following list is some (but not all) of the plants which can be impacted by root knot nematodes:

Alfalfa, African daisies, African violet, almond, apricot, avocado, azalea, banana, barley, bean, blackberry, butterfly flower, cantaloupe, carrot, capsicum, chickpea, cineraria, citrus, coffee, corn, cotton, cucumber, date palm, eggplant, grapes, hemp, hibiscus, hops, hydrangea, Jerusalem cherry, lentil, lettuce, lilac, nectarine, okra, olive, onion, papaya, pea, peach, peanut, pear, pecan, pepper, pigeonpea, pineapple, plantain, plum, potato, primula, pumpkin, raspberry, red clover, rose, soybean, squash, strawberry, sunflower, sweet potato, tea, tobacco, tomato, walnut, and watermelon.

There is a bright side to all of this. A number of nematode-resistant crops are available. Check your seed packets to see if the varieties you plan on planting are nematode-resistant, as these can hold up better to the damage which the tiny parasites inflict.

How To Get Rid Of Root Knot Nematodes

There are few organic solutions for root knot nematodes. Sure, there are nematicides available, but they’re usually only for commercial agriculture and aren’t widely available for home gardening use. So what can you do to eradicate these little parasites?

Organic Root Knot Nematode Control

There are two organic nematicide variants available: ones based on geraniol (the oil of geraniums), and ones based on quillaja saponaria, the soap bark root. Remember, though, that nematicides will kill off both beneficial and parasitic nematodes.

A geraniol compound such as Growers Trust Nematode Control or EcoClear Stop Bugging Me! Nematode Control may be useful for organic gardeners. Growers Trust features geraniol and beneficial bacteria, where EcoClear is geraniol and cinnamon oils.

Quillaja saponaria compounds such as Monterey Nematode Control use the saponins from the soap bark tree to help reduce nematode populations.

You can also use an azdirachtin product such as AzaMax, which is a pure azdirachtin extracted from neem oil. This may work as a light nematicide, but tends to be better against other pests such as spider mites, thrips, aphids, and more.

Add neem seed meal, crab meal, or oyster shell flour to your soil. All three are fertilizers, but they’re great soil builders in the war against root knot nematodes.

Neem seed meal is a gentle fertilizer which is made from the leftover material after making neem oil. It helps reduce a number of pests naturally, plus it breaks down to add low levels of nitrogen to the soil. It also can help strengthen the roots of plants to make them resistant.

Crab meal encourages beneficial soil microorganisms which reduce nematode population. It also helps plants to increase the strength of their cell walls, making them more naturally resistant to many conditions.

Oyster shell flour is in essence a form of diatomaceous earth. While it has less effect when it’s wet, it can help make the soil less hospitable to nematode populations and reduce other pests as well.

Black walnut leaves and hulls have a natural compound in them which is called juglone. This compound is an extremely effective killer of root knot nematodes, but can have an adverse effect on some plants. That’s why there’s few weeds around walnut trees!

If you want to put an organic source of juglone to work in your garden, use fresh walnut leaves or smashed hulls as a thick layer of compost on your bed, or just build a tall pile there. Regularly turn it to keep it composting. I use leaves, as they’re quick to break down.

The juglone compounds will seep into the soil when you wet down the pile, and after three to six months should have broken down enough that they will no longer be toxic to other plants. This also helps wipe out weeds or other pests that may be in your beds during composting.

Environmental Root Knot Nematode Control

Soil solarization is a common environmental method of wiping out nematodes and some species of fungi. However, soil solarization will kill all beneficial nematodes, fungi, or bacteria which are in your beds as well, so this is an option which you should not take lightly.

To solarize your soil, till the soil and flatten it out. Dampen the soil evenly, and then place a thick sheet of clear plastic overtop the soil surface, securing it tightly down so it doesn’t move. Leave the plastic on top of the soil during the hottest months of the year for at least 2-3 months.

After you’ve solarized your soil, it’s important to add back in beneficial mycorrhizal fungi, bacteria, and nematodes. These will help prevent future pest and disease outbreaks.

For beneficial nematodes, I recommend Nature’s Good Guys Live Beneficial Nematodes, which contains three different forms to kill off a wide variety of pests. The Steinernema feltiae species is especially vital for pest control including root knot nematodes.

Marigolds release a natural compound into the soil which is toxic to root knot nematodes. If you plant marigolds as a cover crop between plantings of food crops, you may see a slow and gradual reduction in root knot nematode activity. This works cumulatively in the soil.

Growing marigolds as a cover crop means you will need to till them back into the soil at the end of their growing season. However, this adds more plant matter to the soil, which improves the soil over time. In addition, marigolds are a great companion plant for tomatoes!

Another plant which produces a similar natural compound as a cover crop is sudangrass. Related to sorghum, this grass can reach heights of up to 7 feet tall, so it will need to be mowed regularly to keep it in check.

Leave the grass clippings to break down into the soil, as it will release its nematode protection as it decays. It also adds valuable nitrogen back into the soil. If you’re growing in raised beds, you can use grass shears to keep it trimmed down, and till it under at the end of the season.

Preventing Root Knot Nematodes

Prevention is always the best cure for a pest problem, and root knot nematodes are no exception. So let’s talk about prevention.

First off, plant nematode-resistant varieties. There are a wide variety of different seed suppliers who carry nematode-resistant seed stock, usually notated as an N in the resistance charts.

If you cannot plant nematode-resistant strains, practice good crop rotation. Some species of root knot nematodes are more selective than others. Planting cover crops like marigolds or sudangrass between at-risk crops will also bring down the nematode population.

Remove the roots of old plants when clearing the bed. As root knot nematode juveniles can live in the galls they form on the roots, they will continue to multiply even as the roots are dying out. Removing the remaining root mass can extract those juveniles.

Till the soil 2-3 times in the fall. This breaks up the soil, turning the nematodes up to the surface where they will die off from exposure to the sunlight. This will impact both beneficial and parasitic nematodes, so you may need to re-add beneficial nematodes again in the spring.

Plant overwintering grass cover crops like wheatgrass, ryegrass, or rye. Sudangrass is also good and offers some nematicide properties. Keep these mowed down to a manageable level, and till them under in the spring to add more plant matter to the soil.

Regularly add more organic material to your soil. Adding more composted leaves, grass clippings, and manure to your beds will help naturally control the population of nematodes in the soil, since nematodes prefer living material to decaying plant matter.

Frequently Asked Questions

Q: What are the symptoms of root knot nematodes in plants?

A: That’s difficult to determine, because a very healthy, vigorous plant may show no symptoms at all!

As a general rule, common symptoms of a bad root knot nematode infestation can include chlorosis (yellowing of the leaves/stems), stunted growth, wilting, and a lack of production of fruit.

However, these may be nonexistent to severe depending on the population of nematodes, the health of the plant, the natural resistance of the plant, and any number of other factors in the soil makeup. It can also be hard to separate the symptoms from other pest/disease issues.

The only real way to be sure that it is in fact root knot nematodes is to carefully remove a plant from the soil and examine its roots. If there are a lot of galls growing along the root system, it’s likely root knot nematodes at work.

While these microscopic nematode parasites can be problematic, root knot nematodes are not uncontrollable. They may be tricky, but with good garden management, you won’t have negative consequences! Have you ever battled garden nematodes? Let me know down below!

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