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Garlic Pathogens, Viruses, Nematodes and Arthropods

Introduction

In most commercial and home gardens, softneck and hardneck garlic cultivars are propagated vegetatively. Garlic is propagated vegetatively by planting individual garlic cloves. The cloves are separated from the bulb and planted in the fall, about six weeks before the first frost. Garlic viruses are commonly carried over from one generation of vegetative propagules to the other, while nematodes and arthropods further transmit the pathogens from infected to healthy plants.





What are Pathogens

Pathogens in plants are organisms that can cause disease in plants. A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence. Pathogens are taxonomically widely diverse and comprise viruses and bacteria as well as unicellular and multicellular eukaryotes. They can be divided into four main groups: bacteria, fungi, viruses, and nematodes.

  • Bacteria are single-celled organisms that can cause a variety of diseases in plants, including wilts, blights, and rots.

  • Fungi are multicellular organisms that can cause a variety of diseases in plants, including rusts, smuts, and mildews.

  • Viruses are tiny, non-cellular organisms that can cause a variety of diseases in plants, including mosaics, yellows, and wilts.

  • Nematodes are small, worm-like organisms that can cause a variety of diseases in plants, including galls, knots, and root rots.

Pathogens can enter plants through wounds, natural openings, or by being carried on the wind or by insects. Once inside the plant, they can cause a variety of symptoms, including wilting, yellowing, spotting, and death.


What are Garlic Bacteria

Garlic bacteria are a group of bacteria that can cause disease in garlic plants. They can be divided into two main groups: pathogenic bacteria and beneficial bacteria.

  • Pathogenic bacteria are bacteria that can cause disease in garlic plants. Some common pathogenic bacteria of garlic include:

    • Pseudomonas syringae pv. allii, which causes garlic wilt

    • Erwinia carotovora subsp. carotovora, which causes soft rot

    • Xanthomonas campestris pv. allii, which causes black rot


  • Beneficial bacteria are bacteria that can help to protect garlic plants from disease. Some common beneficial bacteria of garlic include:

    • Bacillus subtilis, which produces antibiotics that can kill pathogenic bacteria

    • Lactobacillus plantarum, which produces lactic acid that can inhibit the growth of pathogenic bacteria

    • Trichoderma harzianum, which is a fungus that can kill pathogenic bacteria


Garlic bacteria can enter plants through wounds, natural openings, or by being carried on the wind or by insects. Once inside the plant, they can cause a variety of symptoms, including wilting, yellowing, spotting, and death.

There are a number of ways to control garlic bacteria. Some common methods include:

  • Using resistant varieties: Some varieties of garlic are resistant to certain bacteria. Planting resistant varieties can help to reduce the risk of bacterial disease.

  • Practicing good sanitation: Good sanitation practices can help to reduce the spread of bacteria. These practices include:

    • Planting garlic in a clean area

    • Using clean tools when planting and harvesting garlic

    • Removing diseased plants from the garden

  • Using pesticides: Pesticides can be used to kill bacteria. However, they should be used with caution, as they can also harm beneficial bacteria.

  • Biological control: Biological control involves using natural enemies, such as predatory insects, to control bacteria.

  • Host plant resistance: Host plant resistance involves planting varieties of garlic that are resistant to bacteria.

If you take steps to control garlic bacteria, you can help to ensure a healthy garlic crop.


What are Garlic Fungi

Garlic fungi are a group of fungi that can cause disease in garlic plants. They can be divided into two main groups: pathogenic fungi and beneficial fungi.

  • Pathogenic fungi are fungi that can cause disease in garlic plants. Some common pathogenic fungi of garlic include:

    • Sclerotium cepivorum, which causes white rot

    • Botrytis cinerea, which causes gray mold

    • Fusarium oxysporum f.sp. cepae, which causes Fusarium basal rot


  • Beneficial fungi are fungi that can help to protect garlic plants from disease. Some common beneficial fungi of garlic include:

    • Trichoderma harzianum, which produces antibiotics that can kill pathogenic fungi

    • Pseudomonas putida, which produces enzymes that can break down the cell walls of pathogenic fungi

    • Gliocladium roseum, which is a fungus that can compete with pathogenic fungi for nutrients


Garlic fungi can enter plants through wounds, natural openings, or by being carried on the wind or by insects. Once inside the plant, they can cause a variety of symptoms, including wilting, yellowing, spotting, and death.

There are a number of ways to control garlic fungi. Some common methods include:

  • Using resistant varieties: Some varieties of garlic are resistant to certain fungi. Planting resistant varieties can help to reduce the risk of fungal disease.

  • Practicing good sanitation: Good sanitation practices can help to reduce the spread of fungi. These practices include:

    • Planting garlic in a clean area

    • Using clean tools when planting and harvesting garlic

    • Removing diseased plants from the garden


  • Using pesticides: Pesticides can be used to kill fungi. However, they should be used with caution, as they can also harm beneficial fungi.

  • Biological control: Biological control involves using natural enemies, such as predatory insects, to control fungi.

  • Host plant resistance: Host plant resistance involves planting varieties of garlic that are resistant to fungi.

If you take steps to control garlic fungi, you can help to ensure a healthy garlic crop.


What are Garlic Viruses

Plant viruses are tiny, non-cellular organisms that can cause a variety of diseases in plants. They are made up of a single strand of RNA or DNA, surrounded by a protein coat. Viruses cannot replicate on their own, and they must infect a living cell in order to reproduce. Plant viruses are spread in a variety of ways, including:

  • Contact with infected plants

  • Insects that feed on plants

  • The wind

  • Water

  • Tools that have been used on infected plants

Once a plant is infected with a virus, the virus can spread throughout the plant through the vascular system. Viruses can also be transmitted to seeds, which can then infect new plants.

There are a number of different types of plant viruses, each of which can cause different symptoms. Some common symptoms of plant virus infection include:

  • Mosaic patterns on leaves

  • Yellowing or spotting of leaves

  • Stunted growth

  • Wilting

  • Death of the plant

There is no cure for plant viruses, and infected plants must be destroyed to prevent the spread of the virus. However, there are a number of ways to control plant viruses, including:

  • Using resistant varieties of plants

  • Practicing good sanitation

  • Using pesticides

  • Quarantining infected plants

Plant viruses can have a devastating impact on crops, and they can also cause problems for ornamental plants. It is important to be aware of the risks of plant viruses and to take steps to prevent their spread.


Garlic viruses are a group of viruses that can infect garlic plants. They are tiny, non-cellular organisms that can cause a variety of diseases in plants, including mosaics, yellows, and wilts.

Some common viral diseases of garlic include:

  • Garlic common latent virus (GarCLV): This virus causes a yellowing of the leaves and a stunting of the plant.

  • Garlic yellows virus (GYV): This virus causes a yellowing of the leaves and a wilting of the plant.

  • Onion yellow dwarf virus (OYDV): This virus causes a yellowing of the leaves and a stunting of the plant.

Garlic viruses are spread through infected plant material, such as bulbs, cloves, and leaves. They can also be spread by insects, such as aphids and leafhoppers.

There are no commercial garlic varieties that are resistant to all garlic viruses. However, some varieties are resistant to certain viruses. Planting resistant varieties can help to reduce the risk of viral disease.

There are no chemical controls for garlic viruses. However, there are a number of cultural practices that can help to reduce the risk of viral disease, such as:

  • Planting garlic in a clean area: This will help to reduce the risk of infection from infected plant material.

  • Using clean tools when planting and harvesting garlic: This will help to reduce the risk of infection from infected tools.

  • Removing diseased plants from the garden: This will help to reduce the spread of infection.

  • Practicing good sanitation: This will help to reduce the risk of infection from infected insects.

Garlic potyvirus is a plant virus that infects garlic plants. It is a member of the potyvirus family, which includes a number of other plant viruses that can cause diseases in a variety of crops. Garlic potyvirus is spread by aphids, which are small, sucking insects.


Potyviruses are the largest group of plant infecting RNA viruses that cause significant losses in a wide range of crops across the globe. The majority of viruses in the genus Potyvirus are transmitted by aphids in a non-persistent, non-circulative manner and have been extensively studied vis-à-vis their structure, taxonomy, evolution, diagnosis, transmission, and molecular interactions with hosts. This comprehensive review exclusively discusses potyviruses and their transmission by aphid vectors, specifically in the light of several virus, aphid and plant factors, and how their interplay influences potyviral binding in aphids, aphid behavior and fitness, host plant biochemistry, virus epidemics, and transmission bottlenecks. We present the heatmap of the global distribution of potyvirus species, variation in the potyviral coat protein gene, and top aphid vectors of potyviruses. Lastly, we examine how the fundamental understanding of these multi-partite interactions through multi-omics approaches is already contributing to, and can have future implications for, devising effective and sustainable management strategies against aphid-transmitted potyviruses to global agriculture.


The virus can also be spread by contact with infected plant material.

Symptoms of garlic potyvirus include:

  • Yellowing of the leaves

  • Stunted growth

  • Reduced yield

  • In some cases, death of the plant

There is no cure for garlic potyvirus. Control measures include:

  • Planting resistant varieties of garlic

  • Using insecticidal soaps or oils to control aphids

  • Removing infected plants from the garden

  • Practicing good sanitation


What are Nematodes

Garlic nematodes are a type of plant nematode that can cause damage to garlic plants. They are microscopic, worm-like organisms that feed on the roots of garlic plants. This can cause the roots to become stunted and distorted, and the plant to become yellow and wilted. In severe cases, the plant may die.


There are several different types of garlic nematodes, but the most common is the stem and bulb nematode. This nematode is found in many parts of the world, and it is a major pest of garlic crops.


Garlic nematodes are spread through infested soil and plant material. They can also be spread by water and by insects. Once they are established in a garden, they can be difficult to control.


There are a number of ways to prevent garlic nematodes from damaging your garlic plants. One way is to rotate your crops. This means planting garlic in a different part of the garden each year. This will help to break the life cycle of the nematodes.

You can also plant resistant varieties of garlic. These varieties are less susceptible to damage from nematodes.


If you think your garlic plants may be infected with nematodes, you can take a sample of the soil to your local Cooperative Extension office for testing. If the test results are positive, you can take steps to control the nematodes. There are a number of nematicides available, but they should be used with caution. They can be harmful to the environment and to beneficial insects.


You can also try biological control. This involves using natural enemies, such as nematode-eating fungi, to control nematode populations.


If you take steps to prevent and control garlic nematodes, you can help to ensure a healthy garlic crop.


What are Arthropods

Garlic arthropods are a group of insects and other invertebrates that feed on garlic plants. They can cause damage to the plants, making them less productive. Some of the most common garlic arthropods include:

  • Aphids: Aphids are small, soft-bodied insects that feed on the sap of plants. They can cause the leaves of garlic plants to yellow and wilt.

  • Flea beetles: Flea beetles are small, jumping beetles that feed on the leaves of garlic plants. They can cause the leaves to look shredded.

  • Slugs and snails: Slugs and snails are mollusks that feed on the leaves and bulbs of garlic plants. They can cause the leaves to look ragged and the bulbs to rot.

  • Garlic bulb mites: Garlic bulb mites are tiny mites that feed on the bulbs of garlic plants. They can cause the bulbs to rot. There are several types of bulb mites that plague garlic and other Alliums, and dry bulb mites are one of the most significant and widespread garlic pests.

  • Garlic / onion thrips: Garlic thrips are small, slender insects that feed on the leaves and flowers of garlic plants. They can cause the leaves to look stippled and the flowers to drop off.

There are a number of ways to control garlic arthropods. Some of the most common methods include:

  • Insecticides: Insecticides can be used to kill arthropods. However, they should be used with caution, as they can also harm beneficial insects.

  • Biological control: Biological control involves using natural enemies, such as predatory mites, to control arthropods.

  • Cultural control: Cultural control involves practices such as crop rotation and sanitation to reduce the population of arthropods.

  • Host plant resistance: Host plant resistance involves planting varieties of garlic that are resistant to arthropods.


Identifying Garlic Pests

Garlic is a delicious and versatile vegetable that is easy to grow in the home garden. However, like all plants, garlic is susceptible to pests. Knowing how to identify and control garlic pests can help you to keep your garlic plants healthy and productive.


Common Garlic Pests

There are a number of pests that can attack garlic plants. Some of the most common include:

  • Aphids: Aphids are small, soft-bodied insects that feed on the sap of plants. They can cause damage to garlic plants by sucking the sap from the leaves and stems. Aphids can also transmit plant viruses.

  • Flea beetles: Flea beetles are small, jumping beetles that feed on the leaves of plants. They can cause damage to garlic plants by eating small holes in the leaves. Flea beetles can also transmit plant viruses.

  • Slugs and snails: Slugs and snails are mollusks that feed on the leaves and stems of plants. They can cause damage to garlic plants by eating large holes in the leaves and stems. Slugs and snails can also transmit plant diseases.

  • Nematodes: Nematodes are tiny, worm-like organisms that feed on the roots of plants. They can cause damage to garlic plants by feeding on the roots and by transmitting plant diseases.

How to Identify Garlic Pests

The first step to controlling garlic pests is to identify the pest. This can be done by inspecting the plants for signs of damage. Some common signs of pest damage include:

  • Yellowing or wilting leaves: This can be caused by a number of pests, including aphids, flea beetles, and nematodes.

  • Small holes in the leaves: This can be caused by flea beetles, slugs, and snails.

  • Large holes in the leaves: This can be caused by slugs and snails.

  • Webbing on the leaves: This can be caused by spider mites.

  • Thick, sticky substance on the leaves: This can be caused by aphids.

Once you have identified the pest, you can take steps to control it.

How to Control Garlic Pests

There are a number of ways to control garlic pests. Some of the most common methods include:

  • Cultural controls: Cultural controls are methods that involve changing the growing environment to make it less favorable for pests. Some common cultural controls for garlic pests include:

    • Planting resistant varieties of garlic

    • Rotating crops

    • Keeping the garden clean

    • Watering the plants at the base of the plant

    • Mulching around the plants


  • Biological controls: Biological controls are methods that use natural enemies to control pests. Some common biological controls for garlic pests include:

    • Beneficial insects, such as ladybugs and lacewings, that prey on aphids

    • Nematodes that prey on slugs and snails


  • Chemical controls: Chemical controls are methods that use pesticides to control pests. Pesticides should be used as a last resort, as they can harm beneficial insects and the environment.



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Growing Garlic from Bulbils

Garlic can also be propagated by planting bulbils. Bulbils are small, bulb-like structures that form on the flower stalks of garlic plants. The bulbils can be planted in the fall or spring. They will usually take two years to mature into full-sized bulbs.


Garlic can be propagated from bulbils, which are small, bulb-like structures that form on the flower stalks of garlic plants. To propagate garlic from bulbils, you will need to:

  • Gather the bulbils from the flower stalks of your garlic plants.

  • Allow the bulbils to dry for a few days.

  • Plant the bulbils in a well-drained soil in the fall or spring.

  • Water the bulbils regularly.

  • Thin the bulbils so that they are spaced 2-4 inches apart.

  • Harvest the garlic bulbs in the spring or summer.

Here are some more details on each step:

  1. Gather the bulbils from the flower stalks of your garlic plants. The bulbils will form on the flower stalks of your garlic plants in the summer. Once the flower stalks have died back, you can cut them off and harvest the bulbils.

  2. Allow the bulbils to dry for a few days. After you have harvested the bulbils, allow them to dry for a few days in a cool, dry place. This will help to prevent them from rotting.

  3. Plant the bulbils in a well-drained soil in the fall or spring. You can plant the bulbils in the fall or spring. If you plant them in the fall, they will overwinter and start growing in the spring. If you plant them in the spring, they will start growing immediately.

  4. Water the bulbils regularly. The bulbils will need to be watered regularly, especially during dry periods.

  5. Thin the bulbils so that they are spaced 2-4 inches apart. Once the bulbils start growing, you will need to thin them so that they are spaced 2-4 inches apart. This will help to ensure that they have enough space to grow.

  6. Harvest the garlic bulbs in the spring or summer. The garlic bulbs will be ready to harvest in the spring or summer. When they are ready to harvest, the leaves will have turned yellow and the tops of the bulbs will have begun to dry out.

A recent breakthrough in the production of true (botanical) garlic seeds resulted in rapid scientific progress, according to an article published at the National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/36298648/


The question of whether viruses are transmitted via seeds remains open and is important for the further development of commercial seed production. They combined morpho-physiological analysis, fluorescence in situ hybridization (FISH), and PCR analysis to follow potyvirus localization and translocation within garlic fertile plants and seeds. Spatial distribution was recorded in both vegetative and reproductive organs. They conclude that garlic potyviruses are translocated to the seeds from the infected mother plant during flower development and post-fertilization, while pollen remains virus-free and does not contribute to seed infection. Therefore, the main practical goal for virus-clean seed production in garlic is the careful maintenance of virus-free mother plants. Although garlic pollen is free of potyviral infection, the male parents' plants also need to be protected from contamination, since viral infection weakens plants, reducing flowering ability and pollen production.


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Mr. Jere Folgert is the owner of GroEat Garlic Farm in Bozeman, Montana. GroEat Farm is a small, sustainable family farm located in the beautiful Hyalite Foothills, in the shadows of the Gallatin Mountain Range. The hardneck varieties that they grow on their farm flourish, due to the combination of the very cold winters, heavy snowpack, moist spring, temperate summers, and the nutrient-rich and dynamic alluvial soils, washed down from the Gallatin Mountain Range.



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