Why Do Your Herbs Have Holes in Their Leaves?


Herbs are a great addition to any dish, providing flavor and potential health benefits, including preventing and managing heart disease, cancer, and diabetes. However, there’s nothing quite as frustrating as finding holes in your perfectly lush and green herbs. Luckily, getting to the root of the problem isn’t as challenging as you might think.

Your herbs have holes in their leaves due to pest damage, fungal diseases, or environmental stressors. Pests such as snails, slugs, and Japanese beetles nibble on leaves, perforating holes. Cercospora and anthracnose are two common fungal diseases that cause hole-y leaves.

Luckily, most of these problems are easily remedied. In this comprehensive guide, I will take a closer look at each potential issue and offer solutions to get your herbs back to their former glory. Buckle up, and let’s get started!

1. Pest Damage

With their lush leaves and inviting aroma, it’s no surprise that pests love herbs as much as we do. Snails, slugs, caterpillars, and Japanese beetles are all common culprits of herb leaf damage. Each of these pests leaves behind a telltale trail of holes in the leaves.

Snails and Slugs

These are the most common culprits of herb leaf damage. Snails and slugs are nocturnal creatures that come out to feast on your herbs under the cover of darkness. They leave behind a slimy trail as they travel and feast on your plants.

Slugs and snails love tender, young leaves and are especially fond of basil, cilantro, and parsley. They perforate holes towards the center of the leaf, starting from the edge. Due to their feeding nature, they leave large, irregular holes behind.

How to Control

Left unchecked, snails and slugs can wreak havoc on your herb garden. The good news is, there are a few simple ways to control these pests.

  • Regularly check your herb plants for signs of snail and slug damage. Look for their telltale slime trails and perforated leaves. Check the underside of the leaves, as this is where they like to hide.
  • Clear away debris from your herb garden, as snails and slugs love to hide in dark, moist places. Staking and trellising your plants can also help as it allows for better airflow and makes it harder for pests to access the leaves.
  • Pick snails and slugs off by hand and drop them into a bucket of soapy water. This is the most effective way to get rid of these pests.
  • Create a barrier around your plants with crushed eggshells, Repels-All, or diatomaceous earth. Repels-All has irritating oils that will deter pests from entering your garden. Diatomaceous earth is a fine powder made from fossilized algae. It works by puncturing the exoskeleton of pests, causing them to dehydrate and die. 
  • Set out traps for snails and slugs, such as beer traps or boards. Beer traps attract pests with the yeast in the beer and then trap them in the container. Boards can be placed around your plants and will trap the pests underneath. Be sure to check the traps regularly and dispose of the pests.

Caterpillars

These voracious eaters can severely damage your herbs, especially if you’re dealing with a large infestation. Caterpillars are the larvae of moths and butterflies, and they love to feast on leaves. They are especially fond of basil, oregano, sage, and thyme. 

Unlike snails and slugs that feed towards the center of the leaf, caterpillars eat throughout the leaf, often starting along the edge. They will leave small, clean-cut holes in the leaves as they feed and lots of dark fecal droppings on the ground.

How to Control

You can control caterpillars by following a few simple methods:

  • Handpick and drop them in soapy water
  • Set out traps such as pheromone traps or barriers
  • Spray plants with Bacillus thuringiensis (BT) or neem oil
  • Encourage beneficial insects such as ladybugs, lacewings, and parasitic wasps. Plant nectar and pollen-rich flowers such as dandelion, cosmos, and marigold to attract these helpful predators to your garden.

Japanese Beetles

These shiny, metallic-looking pests are a destructive force in many gardens. Japanese beetles love to feast on the leaves of herb plants, leaving behind telltale skeletonized leaves. They congregate in large numbers when feeding and completely defoliate plants in a short amount of time. Japanese beetles feed on almost all herbs.

How to Control

You can control Japanese beetles by:

  • Spraying plants with pyrethrin or neem oil
  • Encouraging beneficial insects and parasitic nematodes
  • Handpicking beetles and dropping them in soapy water
  • Spraying a home-made water and soap solution
  • Covering the plants with row covers

Sap Sucking Pests

Aphids, whiteflies, and mealybugs are common sap-sucking pests that can damage herb plants. They have specialized mouthparts that pierce the plant and suck out the sap. This disrupts the plant’s ability to absorb nutrients and water, causing stunted growth and yellowing leaves. Thrips scrape the surface of the leaves, sucking plant juices and causing silver-colored streaks on the leaves.

Common clues of sap-sucking pests are:

  • Honeydew
  • Yellowing or wilting leaves
  • Stunted growth
  • Black sooty mold

How to Control

You can control sap-sucking pests by:

  • Encouraging beneficial insects such as ladybugs, green lacewings, and parasitic wasps.
  • Spraying plants with water at high pressure to knock the pests off
  • Spraying plants with insecticidal soap or neem oil
  • Sprinkling diatomaceous earth around the base of the plant
  • Removing and disposing of heavily infested leaves. Avoid composting as this can spread the pests to other plants.

Animals

Deer, rabbits, groundhogs, and other animals can be a significant problem in the garden, especially if you live in an area with a high population of these creatures. Animals love to eat the leaves of herb plants and can quickly decimate a garden.

How to Control

You can keep animals out of your herb garden by following a few simple methods:

  • Fencing: A tall fence (at least 6 feet or 1.8m) will deter most animals from entering the garden.
  • Netting: Put netting over the plants to keep animals from being able to reach the leaves.
  • Repellents: There are a variety of commercial repellents available like Repels-All, Bobbex, and Hinder that will deter animals from entering the garden.. You can also make your own repellent with ingredients like garlic, hot pepper, or vinegar.
  • Tracking: Check the garden regularly for animal tracks and droppings. This will help you determine what type of animal is visiting your garden so you can take the necessary steps to deter them.
  • Traps: You can set traps for animals like rabbits and groundhogs. Place them strategically around the garden and check them regularly.

2. Fungal Diseases

While most herbs are relatively resistant to disease, they can be susceptible to fungal problems, especially if grown in overly wet or humid conditions. Overhead watering, poor air circulation, and crowded planting can all contribute to fungal issues

Holes from fungal diseases start out as small spots on the leaves that turn into larger lesions. The edges of the holes may be ragged or have a yellow halo. As the disease progresses, the leaves may turn yellow or brown and drop off the plant. Common fungal diseases that affect herbs include:

Cercospora Leaf Spot

Characterized by small, dark brown spots with a yellow halo, Cercospora leaf spot is a common fungal disease that affects herbs. It starts out as small spots on the leaf and then gradually increases as they multiply, enlarge, and merge together. 

The spots eventually turn brown, and the leaves may drop off the plant. Cercospora fungal spores spread through splashing water, wind, and rain and can quickly infect an entire herb plant.

Anthracnose

Anthracnose is a group of fungal diseases that cause small, dark brown or black spots on the leaves of plants. The spots may have a yellow or tan halo, and their edges may be ragged. This condition is usually fuelled by excess water on the leaves, stems, and wet weather. On severe infestation, the leaf tissue dies, and the leaves turn papery and drop off the plant.

How to Control

There are several preventive measures you can take to control fungal diseases:

  • Plant in well-drained soil. Wet, soggy soil is the perfect environment for fungal diseases to take hold. This can lead to root rot, which can kill your plant. To improve drainage, amend the soil with organic matter such as compost or perlite. You can also plant your herbs in raised beds or containers.
  • Avoid overhead watering. Moisture on the leaves provides an ideal environment for fungal spores to germinate and grow. Water your plants early in the day, so the leaves have time to dry before nightfall. You can install drip irrigation or soaker hoses to water your plants at the base to minimize moisture on the leaves.
  • Increase air circulation. Good air circulation helps to dry the leaves and prevent fungal spores from germinating. Improve air circulation around your plants by spacing them adequately apart and pruning any dead or dying leaves. You can also install a fan to blow air across the plants.
  • Remove and destroy infected plants. Fungal diseases spread quickly from plant to plant. Remove and destroy any plants that show fungal infection to nip the problem in the bud. Throw them in the trash and avoid composting, as this can spread the disease to other plants.
  • Practice crop rotation. Crop rotation is the practice of growing different crops in the same space at different times. This helps to break the life cycle of fungal diseases and can also help to improve the quality of your soil.
  • Use fungicides. Fungicides are chemicals that can kill or prevent the growth of fungi. They come in different formulations, including liquids, powders, and granules. Look for fungicides that contain the active ingredient copper for the best results. However, this should be used as a last resort due to the potential adverse environmental impacts.

3. Environmental Stressors

Another common cause of holes in herb leaves is environmental stress. This can include extreme temperatures, drought, or poor growing conditions. Environmental stressors can cause the leaves to dry out, become brittle, and eventually break or tear. They can also make the plant more susceptible to fungal diseases and pests.

Extreme Temperatures

Herbs are generally quite hardy and can tolerate a wide range of temperatures. However, they may still suffer from leaf damage if exposed to extreme temperatures for extended periods. Hot, dry conditions can cause the leaves to wilt, turn brown, and eventually drop off the plant. Cold temperatures can cause water in the leaves to freeze and expand, causing the leaves to rupture.

Drought

Drought is another common environmental stressor that can cause leaf damage. During drought, the soil dries out, and the plants cannot get the water they need to survive. This deprives the leaves of moisture and nutrients, causing them to wilt and die.

Poor Growing Conditions

Herbs can also be damaged by poor growing conditions, such as overcrowding, inadequate lighting, or poor drainage. These stressors manifest as stunted growth, hole-y leaves, and eventually death.

How to Prevent

While you may have less control over the weather, there are several things you can do to prevent or minimize leaf damage caused by environmental stressors.

  • Water deeply and infrequently: Watering deeply and infrequently encourages plants to develop deep roots that can access water even during periods of drought. Avoid getting water on the leaves to prevent fungal diseases.
  • Mulch: Mulching helps to conserve moisture, deter weeds, and regulate soil temperature. Use organic mulches, such as straw, wood chips, or leaves, to provide the best results. Over time, organic mulches will also improve the quality of your soil as they decompose.
  • Amend the soil: Improve the quality of your soil by adding organic matter, such as compost or manure. This will help improve drainage and aeration while also providing plant nutrients.
  • Use row covers: Row covers can provide protection from extreme temperatures and pests. They form a protective barrier around the plants and can be made from various materials, such as fabric or plastic.
  • Grow herbs in a terrarium: A terrarium is an enclosed garden that can provide the perfect growing environment for delicate herbs. By controlling the temperature, humidity, and light, you can create a microclimate ideal for your plants.

Can You Eat Herbs with Holes? 

You can eat herbs with holes, as long as you wash them thoroughly first. While the herbs will appear unattractive, the holes will not affect the flavor or nutritional value of the plants. If you’re concerned about aesthetics, you can cut off any damaged leaves before cooking or serving.

Washing your herbs is essential to remove any dirt, debris, or pests that may be present. Fill a dish with cold water and gently swish the herbs to rinse them. Allow the herbs to drain in a colander or on a clean towel before using.

If you’re looking for a way to use damaged herbs, you can always make pesto or herb-infused oil. These recipes will allow you to use the entire herb, including the leaves, stems, and flowers. You can also dry or freeze herbs for future use.

How to Grow Healthy, Vigorous, and Attractive Herbs

Proper care of your herbs is the best way to prevent leaf damage. By growing healthy, vigorous plants, you can minimize the impact of environmental stressors and pests.

Here are a few tips to help you grow healthy herbs:

  • Choose the right location. Herbs need full sun to thrive, so choose a spot in your yard or garden that gets at least 6 hours of sunlight per day.
  • Prepare the soil. Herbs prefer well-drained, sandy soil. If your soil is heavy or clay-like, you can improve drainage by adding organic matter, such as compost or manure. Remove debris and rocks from the planting area to ensure good aeration.
  • Start with healthy plants. When buying herbs, look for green and vibrant plants. Avoid any that are wilted, discolored, or have yellowed leaves.
  • Plant herbs in the spring. Spring is the best time to plant herbs, as they will have the entire growing season to establish themselves before winter.
  • Space adequately. Overcrowding can stress the plants and make them more susceptible to disease. Adequate spacing improves air circulation and allows the plants to grow to their full potential.
  • Water regularly. Herbs need 1-2 inches (2.54 – 5 cm) of water per week, depending on the weather and soil type. Water early in the day to give the plants time to dry off before nightfall. Inspect the moisture level of the soil before watering to avoid overwatering.

Conclusion

Herbs are a versatile and flavorful addition to any dish. However, sometimes your herbs can have holes in their leaves. Pests, fungal diseases, and environmental stressors can all cause leaf damage. 

To prevent holes in your herbs, control pests promptly, water regularly, and choose the right location for your plants. If you do find that your herbs have holes, don’t worry! They’re still safe to eat as long as you wash them thoroughly. You can also use damaged leaves in pesto or herb-infused oils. With proper care, you can grow healthy, vigorous, and hole-free herbs.

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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