From midsummer through fall, dazzlingly diverse dahlias (Dahlia spp.) fill gardens with flowers of button to dinner-plate dimensions in every shade but blue and in color combinations too numerous to count. Grown as perennials in U.S. Department of Agriculture plant hardiness zones 7 through 10, they are lifted for winter storage elsewhere. Dahlias often attract two damaging black bugs: black bean aphids and thrips.
Dahlias are one of the most popular flowers grown in home gardens Their vibrant colors and unique forms make them stand out in any landscape. However, these showy blooms also attract tiny black bugs that can damage the plants Learning how to identify and control these common dahlia pests is key to growing healthy plants and maximizing flowers.
What Are the Tiny Black Bugs on Dahlias?
There are two main tiny black bugs that feed on dahlias
Aphids
Aphids are small, soft-bodied insects that suck sap from the leaves and stems of plants. They come in a variety of colors, including green, black, brown, red, and yellow. Aphids secrete a sticky substance called honeydew that attracts other insects and can lead to the growth of sooty mold fungus.
On dahlias, aphids tend to cluster on the undersides of leaves and at the tips of stems. They cause distorted growth, yellowing leaves, and stunted plants. Aphids can also spread viral diseases.
Thrips
Thrips are tiny, slender insects that rasp and suck juices from leaves, buds, and flowers They are usually black or brown in color. Thrips damage shows up as silvered or dried areas on leaves and discolored flowers They can stunt plant growth and reduce flowering.
Thrips tend to hide in tightly closed buds and other crevices on dahlia plants. Their feeding results in deformed blooms with dark scarring. Heavy infestations can cause flowers to drop.
How to Identify Tiny Black Bug Damage on Dahlias
Watch for these common signs of tiny black bug infestations on your dahlias:
- Distorted, curled, or yellowing leaves
- Stunted plant growth
- Sticky secretion on leaves and stems
- Sooty mold fungus on leaves
- Wilting or dropping flowers
- Scarred, discolored, or deformed blooms
- Small black insects clustering on undersides of leaves and on stems
Check all parts of the dahlia plant closely, especially the undersides of leaves and inside unopened buds, to spot the tiny pests. Use a magnifying glass to inspect for small black specks that move around quickly.
Effective Ways to Get Rid of Tiny Black Bugs on Dahlias
Once you confirm the presence of aphids, thrips, or other tiny black bugs, take action right away to limit damage. Here are some effective organic control methods:
Remove by Hand
For light infestations, manually remove the bugs by spraying plants with a strong blast of water or wiping them off with a damp cloth. Check plants daily and crush any bugs you find. Be sure to get underneath leaves and into crevices.
Use Horticultural Oils and Insecticidal Soaps
Coating plants with lightweight horticultural oils or insecticidal soaps suffocates many soft-bodied insects. For best results, spray all plant surfaces thoroughly, especially the undersides of leaves. Apply weekly until pests are under control.
Attract Beneficial Insects
Natural predators like ladybugs, lacewings, and parasitic wasps will feed on aphids, thrips, and other small insects. Attract these beneficial bugs by planting pollen and nectar sources like dill, fennel, and cosmos nearby. Avoid pesticides that would kill the good bugs.
Apply Organic Pesticides
For heavy infestations, apply organic insecticides derived from plants like neem oil, pyrethrin, or spinosad. Always follow label directions carefully. Repeat applications may be needed to fully eradicate pests. Be aware these products may also kill beneficial insects.
Control Ants and Remove Honeydew
Ants often herd and protect aphids, so getting rid of ants can reduce aphid numbers. Prune away stems or leaves covered with sticky honeydew secretions since this can attract more bugs.
Remove Damaged Growth
Prune off badly infested leaves, stems, and flowers. This removes pests and egg clusters and prevents spread. Put pruned parts in sealed bags and dispose of them. Sterilize pruners between each cut to avoid spreading pests.
Use Row Covers
Covering plants with fine mesh fabric row covers blocks access by winged aphids and thrips. Install covers in early spring before pests are active. Be sure to allow space for growth and airflow.
Control Weeds
Weeds around the garden harbor pests and diseases. Pull weeds regularly to eliminate places where bugs can overwinter.
Prevent Tiny Black Bugs on Dahlias
Good cultural practices can help avoid problems with aphids, thrips, and other tiny pests:
- Inspect plants frequently and control bugs early before they multiply
- Use drip irrigation to keep foliage dry
- Avoid excess nitrogen fertilization that produces succulent growth attractive to pests
- Clean up fallen leaves, blooms, and other debris around plants
- Rotate dahlia locations each year to prevent pest buildup
- Cover young transplants with floating row covers
Selecting resistant dahlia varieties can also reduce pest problems. Ask your local nursery for recommended resistant cultivars for your area.
Controlling tiny black bugs is vital for growing strong, flowering dahlias. Check plants often and take quick action at the first sign of infestation. Combining good cultural practices with targeted organic treatments will keep your dahlias gorgeous and pest-free all season.
Black Bean Aphids and Control
You may not notice black bean aphids (Aphis fabae) until they mass on your dahlias new stems and leaves, but they have been hanging around for months. The current generation spent the winter and spring as eggs or wingless females on spindletrees, snowball bushes, or mock orange bushes before a generation of winged females migrated to dahlias and other summer hosts.
Black bean aphids drain sap and excrete the leftovers as gooey, transparent honeydew, which often attracts leaf-blackening sooty mold fungus. The females may give birth to five young each day, most of them also pregnant, and they are capable of reproducing within a week. Even worse, the pests can transmit several viruses, including leaf-mottling dahlia mosaic and cucumber mosaic virus. More Like This
At the first sign of an infestation, set your hose spray attachment to jet or strong spray and shower the plant until all the aphids are dislodged. Do this in the early morning so the leaves dry quickly and have less risk of fungal infection. Repeat daily until the aphids are gone. Treat a large aphid population with insecticidal soap, applying it according to package directions but being sure to saturate the infested areas.
What Are The Black Bugs on a Dahlia?
FAQ
What are the tiny black bugs in my dahlias?
Thrips. Description: Thrips are tiny, slender insects with fringed wings, known for their sap-sucking behavior. They are often found on flowers and leaves, causing damage as they feed. Thrips can be various colors, including black, brown, or yellow, and are typically only a few millimeters long.
How to treat mites on dahlias?
Adequate irrigation is important, because water-stressed plants are most likely to be damaged. Broad-spectrum insecticide treatments for other pests frequently cause mite outbreaks, so avoid these pesticides when possible. Sprays of water, insecticidal oils, or soaps can be used for management.
How do I prevent bugs from eating my dahlias?
To help deter these pests, keep the area around your dahlias tidy. This means removing spent flowers, pruned foliage, weeds and other organic matter. Avoid mulching with shredded leaves or straw (both of which attract them). You can try catching earwigs in an upside-down flowerpot filled with moist, shredded leaves.
How do I get rid of tiny black bugs on my plants?
Use A DIY Natural Soap Spray
The soapy residue disrupts the black bugs’ ability to cling to plants, making them less likely to stay and feast. Remember, consistency is key. Reapply the spray every few days or after rain to maintain its effectiveness.