Dahlias are stunningly beautiful, relatively easy plants that produce clusters of luscious blooms from early summer through late fall, but discovering dahlia insect pests on your prized plants is a frustrating, disheartening experience. Read on to learn about insects that like dahlias, and about treating pests that affect dahlias.
Bugs Eating My Dahlias!
Below are the most common insect pests affecting dahlia plants in the garden:
- Thrips – Slender pests with fringed wings, Thrips damage plants by puncturing the leaves and sucking out the juices. Although thrips rarely kill dahlias, they can affect the appearance by causing stippled leaves, leaf drop and stunted growth. Pesticides aren’t usually helpful because the pests move from plant to plant so quickly.
- Spider mites – About the size of a tiny speck of sand, tiny spider mites are difficult to see with the naked eye. You can locate the pests with a magnifying glass, but a magnifying glass usually isn’t necessary because you will notice telltale strands of thin webbing on the leaves. Spider mites are often more apparent during dry, dusty weather.
- Snails and Slugs – Slugs and snails are capable of doing tremendous damage to dahlias and other plants. However, they are easy to spot; they chew large holes in leaves, and they leave slimy, mucous tracks wherever they go.
- Caterpillars – (the larval stages of moths and butterflies) Caterpillars leave no slime, but like slugs, they chew holes in the leaves. They often roll themselves up in leaves, and rolled, curled foliage is a dead giveaway that caterpillars have been feasting on your dahlias.
- Earwigs – Small, brown bugs with evil-looking pincers, earwigs aren’t as intimidating as they look. These dahlia insect pests are active during the nighttime hours and tend to remain hidden during the day. Keep in mind that pesticides are ill-advised. Although earwigs aren’t pretty, they do a good job at keeping aphids and other more harmful pests under control. Trap them with a rolled up newspaper or a short length of old garden hose.
- Grasshoppers - While not a major pest of dahlia, grasshoppers do occasionally feed on the plant's leaves. Using nosema locustae is a safe way to get rid of these insects.
Treating Pests that Affect Dahlias
Proper plant care is the best line of defense against dahlia insect pests, as healthy dahlia plants are more pest-resistant. Water properly and apply fertilizer carefully according to label directions. Keep dahlia beds clear of leaves and other plant debris, which provide hiding places for slugs, snails, earwigs, and other pests. Similarly, limit mulch depth to no more than 3 inches (8 cm.), especially if you notice silvery slug and snail trails. Keep weeds pulled in the area around your dahlias. Prune any damaged plant parts. Large pests like slugs and caterpillars are easy to remove by hand. Remove the pests and drop them in a bucket of soapy water. Evenings or early mornings are the best times for this task, when slugs and caterpillars are more active. Grab a flashlight and be sure to wear gloves to protect your hands. In some cases, wood ashes and diatomaceous earth create scratchy barriers that keep slugs at bay. If caterpillars remain a major problem, consider using Bacillius thuringenesis (Bt), a natural bacteria. When caterpillars eat the bacteria, the toxins give the pests a deadly tummy ache. (Keep in mind that although caterpillars and slugs have similarities, they are very different pests. Bt won’t help alleviate a slug problem, and wood ashes and diatomaceous earth are unlikely to discourage caterpillars.) Avoid pesticides, which are dangerous for bees and other beneficial insects. Many pests, including spider mites, aphids, and thrips are easily treated with an insecticidal soap spray. Reapply every week to ten days if you continue to notice pests on your dahlias. Seek out safe alternatives, such as chemical-free slug pellets. Consider ways to attract birds, frogs, and toads to your yard. They’ll do a great job at keeping caterpillars, slugs, and other pests in check.
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FAQs
Many pests, including spider mites, aphids, and thrips are easily treated with an insecticidal soap spray. Reapply every week to ten days if you continue to notice pests on your dahlias. Seek out safe alternatives, such as chemical-free slug pellets. Consider ways to attract birds, frogs, and toads to your yard.
How to get rid of bugs on dahlias? ›
Keeping your dahlias consistently watered can help discourage them. Insecticidal soaps can temporarily reduce an outbreak. Get more information about this pest and how to control it in this article from the Missouri Botanical Garden: Controlling Thrips Outdoors.
What spray to use on dahlias? ›
Commercial organic sprays or home-made ones using soap, garlic, chilli or botanical oils are effective and generally kind to non-pests.
What does spider mite damage look like on dahlias? ›
The typical sign of 2-spotted red spider mites is yellowing of the most mature leaves, lowest on the plant. The back of the leaves shows a red webbing. While other conditions can turn old leaves yellow, normally the leaves turn yellow all over.
What is a homemade pesticide for dahlias? ›
Oil Spray
Mix 1 cup of vegetable oil with 1 tablespoon of mild liquid soap. Add 2-8 teaspoons of this mixture to 1 quart of water and spray your plants as above. The oil in this spray smothers the insects, so it is effective on aphids, thrips, mites, and scale.
What does Epsom salt do for dahlias? ›
Additional Mid Summer Dahlia Care
Epsom salt, magnesium sulphate, is a useful tonic that enables plants to use nitrogen more effectively. Add up to one tablespoon per gallon either as a drench or in spray. Use regularly in a low dose rather than occasionally at a higher dose to avoid jumps in the health of the dahlias.
Do coffee grounds help dahlias? ›
Yes! Dahlias like coffee grounds and the coffee grounds make for a wonderful fertilizer. Since coffee grounds usually contain about 2% nitrogen, a third percent of phosphoric acid, and roughly 1% of potassium, the coffee grounds act as an excellent fertilizer for your dahlia garden.
Can you use Miracle Grow on dahlias? ›
Begin feeding dahlias with Miracle-Gro® Performance Organics® Blooms Plant Nutrition every seven days after planting (be sure to follow label directions). Designed specifically for flowers, it goes easy on the nitrogen (which encourages lots of leaves) and contains more of the phosphorus needed for beautiful flowers.
What is the common disease on dahlias? ›
Powdery mildew, Erysiphe. White powdery spots or patches develop on leaves and occasionally on stems. Symptoms often first appear on the upper surfaces of the leaves and are usually most pronounced during hot, humid weather. Heavily infected leaves turn brown and shrivel.
Can a plant recover from spider mites? ›
Plants with mite damage limited to a few leaves will usually recover without special care. But plants stressed by more significant spider mite damage will require extra attention. Make sure your plant gets the appropriate amount of sunlight. Keep soil moisture consistent so the soil is never soggy or too dried out.
Earwigs These creepy-crawly insects feed on decaying plant matter. Unfortunately, they also like munching on tender dahlia leaves and flower buds. Earwigs are largely nocturnal and during the day they like to hide among clusters of emerging leaves.
Do coffee grounds deter slugs? ›
Diluting brewed coffee with an equal part water is plenty to do the job. Coffee grounds have been recommended in the past as an organic method to keep slugs and snails out of your flower and vegetable beds. Grounds will repel slugs, but the USDA research team confirms that a caffeine solution is more effective.
What not to plant with dahlias? ›
Cattails, flag iris, marsh marigolds, and rush reed plants thrive in soils that stay soggy all year long and make poor companions for dahlias. Plants that prefer drier soils or desert climates also are not a great match with dahlia.
What kills slugs instantly? ›
Pouring salt on a slug will kill it in a matter of seconds, however, it generally takes quite a bit of salt to do so. The salt kills the slug through osmosis – it draws water from inside the slug and rapidly dehydrates it.
How do I protect my dahlias from aphids? ›
Encourage natural predators like ladybugs, lacewings, damsel bugs, or hoverflies. If necessary, spray affected plants with neem oil or a ready-to-use insecticidal soap, ensuring complete coverage, especially under leaves where aphids congregate.
What are the little brown bugs on my dahlias? ›
Most likely thrips. Thrips are very small brown bugs which are hard to see but cause loads of damage- they really like white/pastel colored dahlias. If you think you might have thrips, but aren't sure- shake your flower over a white piece of paper. The thrips will fall out and be brown specks.
