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Viburnums are a diverse group of flowering shrubs that are very popular in the garden. Unfortunately, they’re often preyed upon by a wide range of pests. Keep reading to learn more about the insects affecting viburnums and how to go about controlling viburnum insect pests.
If you’ve noticed bumpy waxy deposits on the stems and leaves of your arrowwood viburnum shrub, you likely have an infestation of scale insects These small sap-sucking bugs can be extremely difficult to remove once they’ve settled in on a plant. Thankfully, with some persistence and the right treatment methods, you can get rid of scales on arrowwood viburnums and restore the health of your shrubs
What Are Scale Insects?
Scales are small, immobile insects that attach themselves to stems, branches, and leaves to feed on plant sap. There are over 8000 species of scales, but some of the most common types that affect viburnums are:
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Oystershell scale – Small (1/8 inch), elongated, brownish-gray scales that resemble oyster shells. They attach to stems and suck the sap.
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Cottony cushion scale – Large (1/4 inch) brownish insects covered in a white, fluffy wax secretion. They primarily feed on leaves.
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White peach scale – Circular, flat, white scales about 1/8 inch wide. Feed on leaves and stems.
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Calico scale – Flat, oval scales in shades of yellow, orange, brown and black. Infest leaves and stems.
Though tiny, scales can occur in large numbers and quickly overwhelm plants. Their sap-sucking feeding habits deprive the plant of nutrients and sugars. Heavy infestations lead to yellowed, stunted growth, leaf drop, branch dieback, and sometimes even the death of the shrub if left uncontrolled.
Signs of a Scale Infestation
The most obvious sign of scale bugs is the presence of the insects themselves on the plant’s stems and leaves. But here are some other clues that your viburnum may have scales:
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White wax deposits or bumps on branches and leaves
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Sticky sap oozing from branches
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Premature leaf drop
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Yellowed foliage
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Dieback of stems and branches
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General lack of vigor in the plant
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Ant trails – ants feed on the honeydew secreted by scales
Carefully check the undersides of leaves and crevices in the bark to spot the bugs. Infestations often start at branch crotches and slowly spread.
How to Get Rid of Scales on Viburnum Shrubs
Eliminating scale insects takes persistence and repeat applications of treatment. But with diligence, you can eradicate these plant pests. Here are some effective organic and chemical options:
Prune Infested Areas
Pruning away heavily infested stems and branches can eliminate a portion of the scale population. It also promotes new healthy growth. Prune in late winter/early spring before bugs become active. Disinfect shears between cuts with rubbing alcohol to prevent spreading scales.
Apply Horticultural Oils
Horticultural oils smother and suffocate scale insects. They are highly effective against all life stages. Spray plants thoroughly in early spring before buds open, coating stems, branches, and twigs. Make 2 more applications at 10-14 day intervals to kill newly hatched nymphs. Follow label directions.
Use Insecticidal Soaps
Like horticultural oils, insecticidal soap sprays suffocate scale bugs and their eggs. For best results, completely drench all plant surfaces, including leaf undersides until droplets form. Reapply every 5-7 days for 2-3 weeks. Insecticidal soaps are safe for people and pets when used as directed.
Apply Neem Oil
Extracts of neem oil disrupt the growth and reproduction of scales. Combine with a small amount of insecticidal soap and spray plants, including the undersides of leaves. Reapply every 7-10 days for 3-4 weeks. Neem oil is non-toxic when used as directed.
Use Systemic Insecticides
Systemic insecticides like imidacloprid are absorbed by the roots and distribute the insecticide throughout the plant. This provides longer control of scale insects as they feed. Apply as a soil drench around the root zone in early spring according to label directions.
Release Beneficial Insects
Lady beetles, green lacewings, and parasitic wasps are natural predators of scale bugs. Releasing them around infested plants in early spring can provide biological control of scales. They may take longer to see results, but using beneficial insects is environmentally friendly.
Apply Horticultural Grade Mineral Oil
This highly refined mineral oil suffocates scale insects, disrupting their metabolism when sprayed directly on bugs. Thorough coverage is key. Spray in early spring before new growth emerges and temperatures are above 40°F. Two more applications at a 10-14 day interval may be needed for total control. Avoid spraying open flowers which may be damaged.
Use Insect Growth Regulator (IGR) Products
IGRs like pyriproxyfen disrupt the growth and reproduction of scale insects. They are absorbed by plants and provide long-term protection against reinfestation. Apply according to label in early spring before scale activity resumes. Combining with horticultural oil enhances effectiveness. IGRs have very low toxicity to beneficial insects.
Tips for Preventing Scales on Viburnum
Here are some tips to help prevent scales from ever becoming a problem in the first place:
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Inspect new plants closely before purchase and avoid those with signs of scales. Quarantine new plants away from existing shrubs.
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Promote plant health with proper planting, watering, fertilization, and pruning. Healthy shrubs can better withstand pest attacks.
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Control ants around shrubs, as they spread scales and feed on their sugary secretions. Trim nearby trees and shrubs to increase sunlight and airflow.
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Monitor viburnums routinely and treat scales early before they multiply.
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Apply a dormant oil spray in late winter before insects become active.
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Rotate treatment options to prevent scales from developing resistance. Combine methods like oils and insecticidal soap for better control.
With persistence and repeated applications, you can remove destructive scale pest from arrowwood viburnums. Consistent monitoring and prompt treatment at the first signs of scales are key to protecting plant health. Avoiding excessive use of broad spectrum pesticides will also preserve populations of beneficial insects that help control scale infestations.
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Common Pests on Viburnum
Here are some of the most common viburnum pests and methods for viburnum pest control. Aphids – While they don’t cause much damage, aphids can cause curling in new growth. They can be gotten rid of with a steady stream of water from the hose, insecticidal soap, or horticultural oil. Thrips – Thrips can cause purple spots on leaves, curled and dropped leaves, and dropped, unopened flower buds. Try to prevent thrips by keeping weeds under the shrub to a minimum. Spray with insecticidal soap, if necessary, but be careful, as there are many beneficial insects that feed on thrips. You can also introduce beneficial insects such as lacewings, ladybugs, and predatory mites to the garden. Southern Red Spider Mites – The leaves turn gray/brown and drop when these red spider mites are present. Mites can be knocked off with a strong spray from the hose or treated with insecticidal soap. Scale – Armored scale cause leaf drop, discolored leaves, and stunted growth. Light infestations of scale bugs can be scraped off by hand, and heavier ones can be treated with insecticide. Other insects affecting viburnums include: Weevils – Weevils chew on the edges of leaves. While they’re not usually dangerous, the damage isn’t pretty. Spray the leaves and ground below the shrub with insecticidal spray to kill the adults. Repeat every two to three weeks to kill each generation. Asiatic Garden Beetles – Flowers, leaves, and new growth is skeletonized when Asiatic garden beetles are around. Common types include the Japanese beetle. Remove adults by hand and introduce nematodes to the soil. Dogwood Twig Borers – Dogwood borers will dig out holes in the stems, leaving sawdust behind. Crush eggs in early summer. Stick a wire into every hole you find to kill the borer inside. Viburnum Leaf Beetles – Plant resistant viburnum varieties to avoid viburnum leaf beetles. Prune away egg-infested branches during the winter. Introduce lacewings as beneficial insects.
The COMPLETE Guide to Getting Rid of Scale Insects
FAQ
How to treat scale on viburnum?
What is the white scale on my viburnum?
What kills scale on shrubs?
Should arrowwood Viburnum be pruned?
Arrowwood viburnum shrubs don’t need extensive pruning. Right after the plant is done flowering, prune any stems necessary to maintain the shrub’s shape. Avoid taking off more than a third of the shrub’s overall size. Remove any dead, damaged, or diseased portions of the shrub whenever you spot them.
How do you care for arrowwood Viburnum?
Fertilize annually in the spring with balanced, slow-release fertilizer or compost. Arrowwood viburnum grows well in full sunlight to partial shade, meaning it needs at least roughly 4 hours of direct sunlight on most days. In hot climates, shade from the strong afternoon sun is ideal. Too little sun can impede flowering.
Why is my arrowwood Viburnum not blooming?
Arrowwood viburnum bears showy white spring flowers that stretch roughly 2 to 4 inches across. The flowers do not have much fragrance. In the fall, the shrub’s foliage turns to shades of yellow, orange, and red. If your shrub does not bloom, the culprit can be lack of sunlight, lack of nutrients, or improper pruning.
What does arrowwood Viburnum look like?
This shrub bears showy white flowers and blue-black fruits. Arrowwood viburnum thrives in temperate conditions, preferring full or partial sunlight and moist but well-draining acidic soil.