Arrowwood viburnum shrubs are prized for their showy flowers and berries that add interest to gardens. However, slugs can be a major pest that damages these plants. Read on to learn identification tips, preventative measures, and control methods to eliminate slugs from your arrowwood viburnums.
Recognizing Slug Damage
The first step is confirming you have slugs damaging your viburnums Look for these signs
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Irregular holes in leaves, leaving a “shotgun” pattern of damage Slugs rasp away leaf tissue as they feed at night.
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Silvery slime trails on leaves and stems The mucus slugs secrete allows them to travel over plants and the ground
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Chewed or missing seedlings. Tender new growth is a magnet for slugs.
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Presence of slugs near soil level, under debris, and on plant parts. Look for the slimy pests on overcast days.
Thoroughly inspect the undersides of leaves and lower branches. Make positive identification before taking action.
Cultural Practices to Deter Slugs
Implementing smart gardening practices makes your landscape less hospitable to slugs:
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Eliminate hiding spots by clearing away leaves, mulch, and weeds around plants.
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Remove slug eggs and young slugs by hand whenever found. Check under boards or pots.
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Use coarse, gritty mulch that slugs avoid rather than moist organic mulch.
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Water plants in the morning so foliage dries out by evening when slugs are active.
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Improve drainage in slug-prone areas of the garden. Avoid standing water.
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Remove slug attractants like pet food, dropped fruit/vegetables, and bird seed spills.
With small adjustments, you can discourage slugs from congregating and feeding on choice plants like viburnums.
Physical Barriers to Stop Slugs
Use physical barriers to protect viburnums from slug damage:
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Copper tape wrapped around planters or bordering beds repels slugs. The metal reacts with the slug’s body to deliver a mild shock.
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Diatomaceous earth sprinkled around plants cuts through a slug’s body, causing dehydration and death. Reapply after rain.
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Crushed eggshells create an abrasive and sharp barrier when scattered nearby.
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Commercial slug fences send a mild electric current through the soil to deter slugs. Install per manufacturer instructions.
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Gravel, sand, or ash borders stop slugs from reaching plants above ground.
Renew barriers regularly for sustained protection. Combine with other methods for best control.
Trapping Slugs to Reduce Populations
Traps capture slugs already within planting beds:
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Beer baits lure slugs into drowning. Sink cups flush with the soil and refill with cheap beer every few days.
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Dump out slugs that accumulate overnight in upturned flower pots atop tile or wood boards.
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Place boards, grapefruit halves, cabbage leaves, or lettuce in the garden. Check under these nightly to remove slugs that gather.
Trapping must be ongoing to decrease slug numbers. Release or destroy captured slugs immediately.
Organic Slug Killers
When slug populations are high, use organic sprays or baits:
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Iron phosphate bait is non-toxic to people and pets but lethal to slugs and snails when ingested.
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Horticultural vinegar or salt spray deters slugs through taste aversion. Avoid plant contact. Reapply after rain.
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Diatomaceous earth-based products like Sluggo combine abrasive effects with bait to control slugs.
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Spinosad bait utilizes natural soil bacteria deadly to slugs but harmless to other organisms when used as directed.
Spot treat infested areas in the evening when slugs are active. Reapply products as needed.
Create a Slug-Free Zone
Vigilance is required to make viburnums and other choice plants “off limits” to slugs. Scout regularly for the pests, signs of damage, and conditions attracting them. Address issues promptly to avoid slugs overwhelming your garden. With persistent monitoring and multiple control methods, you can defeat slugs and keep arrowwood viburnum shrubs protected.
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Local viburnum leaf beetle activity
Between the 2019 and 2020 growing seasons, several residents in Livingston County contacted the local MSU Extension office with descriptions of leaf-feeding damage to viburnum shrubs. Some of them brought samples or sent a photograph. In each case, the leaf damage appeared to be caused by an invasive insect called the viburnum leaf beetle, Pyrrhalta viburni. In early June 2019, one client arriving with a sample of holey leaves and live viburnum leaf beetle larvae, said the larvae had “devoured all the leaves on my [arrowwood] viburnum last spring and are doing it again this year.”
This is a good example of the intensive defoliation that can be caused by viburnum leaf beetle (VLB). Volunteers at the MSU Extension statewide lawn and garden hotline (1-888-678-3464) also received many calls about VLB damage in June 2019. That July, a Livingston County client brought in a viburnum sample that appeared to have bumpy masses on the twigs indicating that VLB adults had laid eggs.
Now in 2020, the viburnum leaf beetle larvae are back again. If you have any viburnum shrubs now is a good time to look for feeding damage that may vary from a small patch of stripped leaves to what one client reported: “they destroyed 21 plants this past week [in late May].”
Viburnum leaf beetle, native to Europe, was first reported in Michigan in 2008. It has now been found in many locations in the southern half of the lower peninsula of Michigan and is expected to spread across the entire state.
Reviewing an article from Weston et al. 2007, one learns that viburnum leaf beetle is an insect species that only feeds on the leaves of shrubs in the genus Viburnum. It seems to find some species and cultivars of viburnum to be “tastier” than others. It is a double threat for its preferred shrub as both the larvae and adult beetles feed on the leaves. The larvae may defoliate the plant at the beginning of the season, then the adult beetles may defoliate the plant during the second half of the growing season. With so much leaf damage throughout the growing season, there is not much time for the plant to recover and build up nutrients for future growth. Consecutive years of defoliation can cause significant dieback and eventually kill plants.
The Cornell University Viburnum leaf beetle website is a very useful resource and provides a timeline of the life stages of this beetle pest, which can help with identification and management. Some of the basic management strategies listed by this website are described below. The Cornell University Department of Horticulture has taken leadership on researching and describing this insect pest in the United States.
Starting in late April, the younger greenish-yellow VLB larvae feed gregariously on the underside of tender, newly expanding viburnum leaves, skeletonizing the foliage. Damage usually starts on lower leaves with only the midribs and major veins left intact.
As the larvae mature, they grow to about one-third of an inch long, darken and develop a series of dark spots. These larger larvae are more likely to be found feeding on the tops of leaves. Adults will start feeding on the leaves in July and are active until frost.
Photo by Whitney Cranshaw, Colorado State University, Bugwood.org
What’s eating my viburnums and how can I stop it?
Questions about this information? Contact us. June 19, 2020
Updated from an original article written by Mary Wilson, Irene Donne, and Dave Smitley.
The invasive viburnum leaf beetle and larvae have been noticed devouring shrubs in Michigan.
Leaf sample brought into a local MSU Extension office, demonstrating damage from feeding of viburnum leaf beetle larvae. Also, magnified larva brought in with leaf sample. Photos by Irene Donne, MSU Extension.
Simple $1 Dollar Slug Control – How to get rid of slugs!
FAQ
Do slugs like viburnum?
How do I permanently get rid of slugs?
What can I spray on my plants to keep slugs away?
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 a viburnum arrowwood?
Viburnums are notoriously tough plants that require very little special maintenance and care. Southern Arrowwood performs best with occasional pruning to maintain shape and rejuvenate the plant. If you don’t want the plant to spread into a large thicket, keep the suckers at the base pruned away. The best time to prune is after flowering.
Why should you plant arrowwood Viburnum?
If you need one more reason to plant this easy-going shrub, here it is: Arrowwood Viburnum is a host plant for Spring Azure butterflies. A host plant is a specific plant that a bug or butterfly lays its eggs on. Without host plants like Arrowwood Viburnum, we would not have Spring Azure butterflies.
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.