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Common Insects Affecting Herbaceous Perennials

Herbaceous perennials are susceptible to a wide range of insect pests. Here is a breakdown of some of the most common culprits:

Chewing Insects

Caterpillars: These voracious feeders can defoliate plants quickly. They come in various colors and sizes. Look for holes in leaves or chewed edges.

Examples: Cabbageworms, cutworms, armyworms.

Sawflies: The larvae of sawflies resemble caterpillars but have more prolegs (unjointed legs). They can skeletonize leaves or cause extensive defoliation.
Beetles: Many beetles, both adults and larvae, feed on perennials.

Japanese Beetles: These metallic green beetles are notorious for skeletonizing leaves.
Flea Beetles: Tiny beetles that jump when disturbed. They create small holes in leaves.
Cucumber Beetles: (Spotted and striped) Feed on leaves, flowers, and fruits. Can also transmit diseases.
Weevils: Adults feed on foliage, while larvae attack roots. (e.g., Black Vine Weevil)

Grasshoppers: These hopping insects can cause significant damage to foliage.
Earwigs: Primarily nocturnal, they chew on leaves and flowers.

Sucking Insects

Aphids: Small, soft-bodied insects that cluster on stems and leaves. They suck plant sap, causing distorted growth and weakening the plant. They can also transmit viruses.
Spider Mites: Tiny, almost invisible pests that cause stippling on leaves. Severe infestations can lead to webbing and leaf drop.
Thrips: Slender insects that rasp plant tissue and suck sap. They cause distorted growth, silvering of leaves, and can transmit viruses.
Whiteflies: Tiny, white, moth-like insects that fly up when disturbed. They suck sap and excrete honeydew, which can lead to sooty mold growth.
Scale: These insects appear as bumps on stems and leaves. They are immobile and protected by a hard shell. They suck sap, weakening the plant.
Mealybugs: Soft-bodied insects covered in a white, waxy coating. They suck sap and excrete honeydew.
Leafhoppers: Small, wedge-shaped insects that jump when disturbed. They suck sap, causing stippling and leaf curling.

Boring Insects

Borers: These insects tunnel into stems, trunks, or roots, disrupting the plant's vascular system and weakening its structure.

Examples: Iris borers, squash vine borers.

Other Insects

Leafminers: The larvae of these insects tunnel within leaves, creating winding trails.
Slugs and Snails: Not insects, but these gastropods can cause significant damage by chewing on leaves and flowers.

Signs of Insect Damage:

Holes in leaves
Chewed edges on leaves
Stippling (small spots) on leaves
Distorted growth
Wilting
Leaf drop
Webbing
Honeydew (sticky substance) on leaves
Sooty mold (black fungus) on leaves

Managing Insect Pests:

Identify the pest: Accurate identification is crucial for effective control.
Monitor regularly: Check plants frequently for signs of insect activity.
Cultural controls:

Choose healthy plants.
Provide proper growing conditions (light, water, fertilizer).
Keep the garden clean and free of debris.
Practice crop rotation.

Biological controls: Encourage natural predators like ladybugs, lacewings, and parasitic wasps.
Insecticides: Use insecticides judiciously and only when necessary. Choose the least toxic option that is effective against the target pest.
Integrated Pest Management (IPM): Combine different control methods for a more sustainable and effective approach.

If you are having trouble identifying a pest or determining the best control method, consult with your local extension office or a gardening professional. They can provide specific recommendations for your situation.

Herbaceous perennials are a popular choice for gardeners because they come in a wide variety of colors, shapes, and sizes. They can also provide years of enjoyment with minimal care. However, herbaceous perennials are susceptible to a variety of insect pests. Knowing how to identify and control these pests is essential for maintaining healthy and beautiful plants.

Common Insects Affecting Herbaceous Perennials

There are many different types of insects that can affect herbaceous perennials. Some of the most common include:

Insect	Host Plants	Damage	Time of Year Most Active
Aphids	Sweet pea, other legumes; snowball viburnum; spirea; many flowering plants	These small, soft-bodied insects suck sap from plants, causing distorted growth, yellowing leaves, and stunted growth. They also excrete a sticky substance called honeydew, which can attract ants and lead to the growth of sooty mold. Ants may protect aphids from natural enemies.	Most active in spring.
Scales	Ferns, orchids, schefflera, crossandra, zebra plant, weeping fig, citrus, ivy, and holly	These insects appear as bumps on stems and leaves. They are immobile and protected by a hard shell. Scales suck sap from plants, causing wilting, yellowing, and stunted growth. Ants may protect scales from natural enemies.	Many active in spring.
Mealybugs	Fruit trees (especially citrus), grapes, woody ornamentals, herbaceous perennials (including cactus, coral bells, figs, flax grasses, fuchsia, gardenia, hibiscus, jasmine, Miscanthus grasses, and oleander)	These soft-bodied insects are covered in a white, waxy coating. They suck sap from plants, causing similar damage as scales. Mealybugs also excrete honeydew. Ants are likely to be found feeding on the honeydew. Ants may protect mealybugs from natural enemies.	Peak populations in spring and autumn.
Leafhoppers	Members of the aster family (Aster, Coreopsis, and Echinacea)	These small, wedge-shaped insects are often green or brown. They suck sap from plants, causing stippling, discoloration, and leaf curling. Leafhoppers can also transmit plant diseases.	Present from late May through early October.
Whiteflies	Cannas, bearded iris, petunia, coleus, and lantana	These tiny, white, moth-like insects fly up when disturbed. They suck sap from plants, causing yellowing, wilting, and stunted growth. Whiteflies also excrete honeydew.	Most active in mid-to-late summer.
Spider mites	Roses, geraniums, petunias, and chrysanthemums	These tiny pests are difficult to see with the naked eye. They cause stippling on leaves, and severe infestations can lead to webbing and leaf drop. In addition to direct feeding damage, spider mites can also transmit plant viruses.	Become numerous in June through September.
Thrips	Chrysanthemums, daisies, daylilies, irises, peonies, roses, and strawberries	These slender insects rasp plant tissue and suck sap. They cause distorted growth, silvering of leaves, and can transmit viruses.	Most active April–September.
Caterpillars	Ferns	These voracious feeders can defoliate plants quickly. They come in various colors and sizes. Look for holes in leaves or chewed edges.	Most active in the early morning or late evening.
Beetles	Tansy	Many beetles, both adults and larvae, feed on perennials. Japanese beetles are a common pest that skeletonizes leaves.	Start watching out in May or June into August.
Wasps	Horseradish, fennel, lovage, orpine, tansy, lemon balm, pennyroyal, garlic chives, blackberry, wine grape, lemon basil, and sweet marjoram	Most wasps are beneficial insects that prey on other pests. However, some wasps can cause damage to plants by stripping bark or gnawing on stems.	Most active during the summer months, June to September.
Leafminers	Columbines, goldenrod, perennial sunflowers, daisies, and Veronica	The larvae of these insects tunnel within leaves, creating winding trails. This can reduce the plant's photosynthetic capacity and make it more susceptible to other pests and diseases.	Peak activity periods in mid-late May, late June, and mid-August.
Borers	Annual aster, chrysanthemum, columbine, cosmos, dahlia, delphinium, hollyhock, iris, lily, marigold, rose, salvia, snapdragon, and zinnia	These insects tunnel into stems, trunks, or roots, disrupting the plant's vascular system and weakening its structure.	Emerge in spring or summer.

Preventative Measures There are a number of preventative measures that gardeners can take to protect their herbaceous perennials from insect infestations. These measures include:

Choosing resistant varieties: Some plant varieties are more resistant to insect pests than others. For example, when planting birch trees, consider selecting varieties that are less susceptible to aphids.
Maintaining healthy plants: Healthy plants are less susceptible to insect infestations. This includes providing adequate water, fertilizer, and sunlight. Healthy plants have a better ability to withstand and recover from insect attacks.
Sanitation: Removing plant debris and weeds can help to reduce insect habitat. Cleaning up fallen leaves and other debris can eliminate overwintering sites for many pests.
Monitoring: Regularly inspecting plants for signs of insects can help to catch infestations early. Early detection is key for effective pest control. Many species of aphids cause the greatest damage in late spring when temperatures are warm but not hot.
Crop rotation: Rotating crops can help to disrupt insect life cycles. For example, avoid planting vegetables that leafminers like to eat in the same place each year.

Early detection and monitoring are crucial for effective pest control. Regularly inspecting plants for signs of insects can help to catch infestations early when they are easier to manage.

Damage Caused by Insects The damage caused by insects can vary depending on the type of insect and the plant being affected. Some common signs of insect damage include:

Damage to Leaves

Stippling: Tiny white or yellow spots on leaves caused by insects sucking sap. For example, leafhoppers can cause stippling on a variety of herbaceous plants.
Discoloration: Yellowing, browning, or bronzing of leaves. Aphids can cause discoloration on a variety of plants.
Distortion: Curling, twisting, or stunting of leaves. Thrips can cause distortion on many plants.
Holes in leaves: Chewing insects, such as caterpillars and beetles, can create holes in leaves. For example, caterpillars can cause holes in the leaves of a variety of plants.
Webbing: Spider mites produce fine webbing on leaves. This webbing can be a sign of a severe infestation.
Skeletonizing: Caterpillars can eat the tissue between the veins of leaves, leaving a skeleton-like appearance.
Windowpane feeding: Caterpillars can feed on one layer of leaf tissue between the veins, creating translucent spots that eventually turn brown.

Damage to Stems and Roots

Honeydew: A sticky substance excreted by some insects, such as aphids, scales, mealybugs, and whiteflies. Honeydew can attract ants and lead to the growth of sooty mold.
Sooty mold: A black fungus that grows on honeydew. Sooty mold can reduce the plant's ability to photosynthesize.
Wilting: Caused by insects disrupting the plant's vascular system or reducing its ability to absorb water. Whiteflies can cause wilting on a variety of plants.
Dieback: Death of plant parts, such as stems or branches. Scales can cause dieback on a variety of plants.
Girdling: Wasps can damage the stems of plants like dahlias by stripping bark, potentially girdling the stem, and causing it to die.

Damage to Fruits

Wasps can damage a variety of fruits, including strawberries, grapes, plums, and nectarines. They may attack the fruit directly or feed on it after birds have created an opening.

Insect Control Methods There are a variety of methods that can be used to control insect pests on herbaceous perennials. These methods can be broadly classified as organic or chemical.

Organic Control Methods Organic control methods are those that do not involve the use of synthetic pesticides. Some common organic control methods include:

Handpicking: This involves physically removing insects from plants. Handpicking can be used to remove Japanese beetles from rose bushes.
Washing: Spraying plants with a strong stream of water can dislodge insects. Washing can be used to remove aphids from delicate plants like ferns.
Pruning: Removing infested plant parts can help to control the spread of insects. Pruning can be used to remove leaves infested with leafminers.
Beneficial insects: Introducing or attracting beneficial insects, such as ladybugs, lacewings, and parasitic wasps, can help to control pest populations. Ladybugs can be used to control aphids on a variety of plants.
Insecticidal soap: This is a soap-based insecticide that can be effective against soft-bodied insects. Insecticidal soap can be used to control aphids on plants like roses.
Horticultural oil: This is an oil-based insecticide that can be effective against a variety of insects. Horticultural oil can be used to control scales on plants like hollies.
Neem oil: This is a natural oil that can be effective against a variety of insects. Neem oil can be used to control spider mites on plants like tomatoes.
Diatomaceous earth: This is a powder made from the fossilized remains of diatoms. It can be effective against insects with soft bodies. Diatomaceous earth can be used to control slugs and snails on a variety of plants.
Companion planting: Planting certain plants together can help to repel insects. For example, planting marigolds near tomatoes can help to repel whiteflies.
Barriers: Using row covers or other barriers can prevent insects from reaching plants. Row covers can be used to protect young plants from leafhoppers.

Chemical Control Methods Chemical control methods involve the use of synthetic pesticides. These methods should be used as a last resort, as they can harm beneficial insects and have negative impacts on the environment. Some common chemical control methods include:

Insecticides: There are a variety of insecticides available that can be effective against different types of insects. For example, carbaryl can be used to control aphids on a variety of plants.
Miticides: These are pesticides that are specifically designed to kill mites. For example, insecticidal/miticidal soaps can be used to control spider mites on a variety of plants.
Systemic insecticides: These are insecticides that are absorbed by the plant and can provide longer-lasting protection. For example, neonicotinoids can be used to control scales on a variety of plants.

When using chemical control methods, it is important to be aware of the potential for pesticide resistance. Rotating insecticides can help to delay the development of resistance.

Resources for Identifying Insects There are a number of resources available to help gardeners identify insects on their herbaceous perennials. These resources include:

Online resources: Websites such as BugGuide and Discover Life provide information and images to help identify insects. These websites often have search functions that allow you to filter by plant host, insect type, or damage symptoms.
Extension offices: Local extension offices can provide information and assistance with insect identification. Extension offices often have experts on staff who can help you identify insects and recommend control methods.
Books and field guides: There are a number of books and field guides available that provide information about insects. These resources can help you learn about the life cycles, habits, and damage caused by different types of insects.

Herbaceous perennials can add beauty and enjoyment to any garden, but they are susceptible to a variety of insect pests. By understanding the common types of insects, the damage they cause, and the control methods available, gardeners can take steps to protect their plants. Organic control methods should be the first line of defense, with chemical control methods used only as a last resort. Preventative measures, such as choosing resistant varieties, maintaining healthy plants, and practicing good sanitation, can help to reduce the risk of infestations. Resources such as online databases, extension offices, and books can help with insect identification. By taking a proactive and integrated approach to pest management, gardeners can ensure the health and beauty of their herbaceous perennials for years to come.

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Common Insects Affecting Herbaceous Perennials

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