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Viburnum borers cause serious damage to shrubs in the viburnum family. Learn to identify these insect pests and eliminate them from the landscape with the viburnum borer treatment tips in this article.
Arrowwood viburnum (Viburnum dentatum) is a hardy, easy to grow shrub suitable for a range of landscape uses With showy spring blooms, attractive foliage, and bluish-black berries, it’s no wonder these shrubs are so popular. However, arrowwood viburnums are sometimes plagued by troublesome pests like worms that can damage the plant’s health and appearance. Let’s look at how to identify, prevent, and safely get rid of worms in arrowwood viburnum shrubs.
Identifying Worms on Arrowwood Viburnum
Several different types of worm pests may infest arrowwood viburnums. Here are some of the most common:
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Viburnum leaf beetle larvae – Pale yellowish-green worms with black spots that skeletonize leaves,
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Webworms – Caterpillars that create silky webs and chew foliage.
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Leafrollers – Green, brown, or white worms that wrap leaves with silk shelters.
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Sawfly larvae – Slug-like worms that eat between leaf veins.
Check undersides of leaves and branch tips for signs of worms, including chewed foliage, fecal pellets, or webbing. Confirm the pest identity before treating infestations.
Cultural Control of Worms
Start by implementing smart gardening practices to prevent or reduce worm problems:
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Pick off and destroy any worms or egg masses found on plants.
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Remove and destroy severely infested branches.
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Keep plants healthy with proper watering, fertilization, and pruning.
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Use row covers as physical barriers to exclude moths from laying eggs.
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Attract beneficial insects like birds or parasitic wasps to feed on worms.
Organic Worm Treatments
If worms persist despite preventive measures, use these organic options safely:
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Insecticidal soap – Kills soft-bodied larvae on contact. Spray undersides of leaves.
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Neem oil – Repels and disrupts worms. Mix with water and spray plants.
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Bacillus thuringiensis (Bt) – Bacteria deadly to leaf-eating larvae. Apply to foliage.
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Spinosad – Natural insecticide derived from bacteria. Proven effective and safe for viburnum leaf beetle larvae.
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Horticultural oil – Smothers and kills eggs and tiny larvae. Coat plants thoroughly.
Always follow label directions when applying organic pesticides. Make repeat applications on a 7-14 day schedule to control successive generations.
Chemical Worm Treatments
For severe worm infestations, these chemical options may be warranted:
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Carbaryl – Broad-spectrum insecticide that kills larvae on contact. However, it is also toxic to beneficial insects and pollinators.
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Chlorantraniliprole – Reduced-risk insecticide effective on viburnum leaf beetle larvae with lower impact on beneficials compared to other chemicals.
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Cyclaniliprole – Systemic insecticide absorbed by plants and ingested by pests. Provides protective control of key viburnum pests for several weeks.
Carefully weigh risks and benefits when using chemical worm treatments. Avoid spraying insecticides during bloom season to protect pollinating bees. Always follow label precautions.
Preventing Reinfestations
Don’t let your efforts go to waste. Stop worms from returning and re-damaging arrowwood viburnum shrubs with these tips:
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Remove egg masses and overwintering worms from plants and soil surface.
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Dispose of infested debris immediately to break pest life cycle.
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Apply horticultural oil dormant spray to suffocate overwintering eggs.
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Rotate treatment modes to reduce pest resistance.
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Time treatments to coincide with larval emergence.
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Maintain plant health and vigor to withstand pest pressure.
When to Call a Professional
Contact a licensed pest control professional if:
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Worm damage is rapidly spreading.
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Multiple treatments have not resolved the issue.
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You are unsure of exact pest identification.
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Large viburnum hedges or plantings need treatment.
Professionals have access to specialized products and equipment to eradicate severe worm infestations. They can also provide advice tailored to your specific situation.
Don’t let worms take the beauty and vibrancy out of your arrowwood viburnum shrubs. Implementing a combination of preventive cultural practices, mechanical removal, organic treatments, and judicious chemical control as needed will help safely knock back worms and maintain healthy plants. Pay close attention year-round and be prepared to take prompt action at the first signs of worms before extensive damage occurs. With persistence and an integrated pest management approach, you can protect your landscape investment and fully enjoy these versatile shrubs.
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Viburnum Borer Life Cycle
So, what are viburnum borers? Viburnum borers are day-flying moths that look a lot like wasps. They have dark bodies with yellow markings and clear wings.
It takes a close inspection to see the difference between the two distinct species of viburnum borers. The clearwing borer has white scales on its face while the lesser viburnum borer lacks the white scales. Both are about one-half inch (1 cm) long with a wingspan of about three-quarters of an inch (2 cm).
The adult moths emerge in early summer. They lay eggs near wounds on the lower part of viburnum trunks, no more than 18 inches (46 cm) above the ground. Pinkish white caterpillars emerge from the eggs and crawl beneath the bark where they feed on the wood and inner bark until they are well-fed and ready to pupate. They become adults about a month after pupating.
You’ll probably notice the damage to your shrubs before you notice the ordinary looking moths. Borer damage on viburnums consists of plant dieback and general decline. You may see small holes on the base of the plants where the adults emerged. It’s not unusual for the plant to die as a result of its injuries.
Control of Viburnum Borer
Stressed and damaged viburnum shrubs attract these borers. Keep the soil around your plants moist, and mulch heavily to prevent cycles of moist and dry soil. Adults lay their eggs near bark injuries which make it easier for the larvae to enter the tree.
Prevent injuries in the bark by avoiding the use of weed whackers near the shrub and directing a lawn mower so that debris flies away from the shrub.
Stop Plants & Leaves Eaten by Worms & Caterpillars
FAQ
What are the little worms on my viburnum leaves?
How do you get rid of worms in shrubs?
How do I get rid of viburnum leaf beetle larvae?
What is the best insecticide for viburnum beetles?
Are arrowwood viburnum shrubs poisonous?
Arrowwood viburnum shrubs don’t have serious issues with most pests or diseases. However, they might be bothered by the viburnum leaf beetle ( Pyrrhalta viburni ). This beetle has become a major problem for viburnum shrubs in Europe and North America. Both the adult beetles and their larvae eat the leaves of the bushes.
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.
Is arrowwood Viburnum a good plant?
Arrowwood Viburnum is a perfect plant for beginner gardeners. It thrives in a wide range of sunlight—from full sun to part shade. Once you’ve found a spot to plant one… Choose a location with well-drained soil and full sun to partial shade.
Can Arrowood Viburnum be potted?
Arrowood viburnum is too large to work well as a container plant. For a potted plant, choose a dwarf variety such as witherod viburnum ‘ Lil’ Ditty’, a cultivar of Viburnum cassinoides. Pot the plant in moist, well-drained soil with an acidic pH.