Viburnum Leaf Beetle belongs to the family Chrysomelidae and Order Coleoptera under the Class Insecta. Female beetles are known for burrowing the terminal twigs and creating cavities in the soft, and spongy parenchyma cells of the stem. They lay their eggs in the same and hide them with excreta. Eggs remain protected in the cavities during severe winter and also from predators. Viburnum beetle typically feeds on the foliage of the genus Viburnum, and both the adult and larva are very selective while eating only the tastier species. The damage is done twice; once when the larva defoliates the plant at the start of growth, and then the adults feed during the peak growing season. With such significant damage, the viburnum plants can't establish themselves. If the defoliation prolongs, viburnum plants wither and are killed, eventually.
Viburnum leaf beetle is native to Asia and Europe, and its specimen was collected in 1924 in Nova Scotia. It was sighted in North America in 1947 in Ontario, Canada. New York reported its first presence in 1996 in a public park. Moreover, The Royal Horticultural Society declared them the worse invasive species in 2010 in the United Kingdom. Viburnum Leaf Beetle spreads across most of the Northeastern United States. Although its infestation is now shifting towards the south, the mild winters southward can potentially stop its spread since Viburnum Beetle eggs need a prolonged chilling period not available in this region.
Viburnum beetle measures between 1/5 to 1/4 of an inch in length. The head, thorax, and elytra are brown whereas, the anterior margin of the elytra is somewhat dark. Its dorsal portion is densely-covered with golden-grey hair. The general appearance of the viburnum beetle is similar to that of the elm leaf beetle except for the dissimilarities in color and size. The elm leaf beetle is larger and with a light brown body and bears a strip on the margin of forewings. Viburnum Leaf Beetle larva measures up to 1/3 inch in length, and color varies from yellowish-brown to light brown with several black dots on the body.
Fortunately, the Viburnum Leaf Beetle can only produce one generation in a year. The Viburnum beetle eggs require a long chilling period and that might be the reason behind its slow reproduction. They overwinter as eggs, and it takes almost two months to become an adult after hatching. Larva appears in early summer that could damage Viburnum leaves for many weeks. Meanwhile, it passes through 3 instars to become an adult in mid-summer. The larva pupates in the soil in summer, and adults could appear in late summer. Usually, a female lays eggs during the late summer and falls into the stem cavities purposely bored for storing eggs for overwintering. Eggs number varies from 5 to 8 eggs per beetle that remain covered with the frass the entire winter that hatch in spring again.
Viburnum Beetle Adult and larva both feed in the midrib region, veins, leaves, and tender shoots skeletonizing them and sometimes leaving oblong holes in the leaves if the feeding was done primarily by the adult-only. The larva also feeds on the undersides of the leaves and tender shoots. Heavy infestation leads to defoliating the entire Viburnum plant. The plants may be killed if the feeding continues for consecutive years. This type of damage is only associated with Viburnum beetle feeding and doesn't resemble the damage of any other pest. Initially, a larva targets the newly emerged leaves and shoots, and then an adult beetle invades the foliage that somehow established during the growing season. This damage causes dieback and then the death of the Viburnum, ultimately.
Viburnum Beetle eggs observe a very long overwintering period, and for this reason, they could only produce one generation in a year. Whenever the environmental conditions become conducive for the eggs hatching and larva, they could harm the Viburnum foliage in your garden. Anyhow, it proves that larva grows faster when the temperatures variate between 63-72°F. Do look them around and monitor if some damage is there or not. However, the larva stops developing when the temperature touches 81°F.
Green Lacewings are the top predatory insects that go after their prey and eat them voraciously. They are equally effective against the Viburnum Beetle larvae and the adults and prey on many slow-moving, soft-bodied insects. Green Lacewings called Chrysoperla rufilabris feed on the larvae when they hatch late summer or early winter. The second round of feeding starts when adults emerge during the peak viburnum growing season in summer. They're very effective for keeping the Viburnum beetle population in control throughout the growing season. 2500 Green Lacewing eggs are enough for a 100-square feet area of the greenhouse, and they could cover up to 5000 square feet when released in the garden.
Green Lacewing eggs hatch in about 4 to 5 days. Releasing them immediately after they have hatched is more beneficial.
BotaniGard contains 22% Beauveria bassiana strain GHA that exists as spores, and when released in the garden, fungal spores grow on the bodies of the insects. They secrete an enzyme that weakens their chitin in a way that they can't shed. Ultimately, they enter the bodies of their host and kill them. Botanigard also produces a variety of toxins such as tenellin, bassianin, and oxalic acid which, act as natural insecticides for controlling the larvae of Viburnum beetles. This parasitism kills the beetles within 5 to 7 days of application. It also causes white muscardine disease in some insects that also get killed.
Add one tablespoon of BotaniGard per gallon of water and spray on the infested plants.
It contains 98.8% mineral oil and can be used during dormant periods only. The best application time against Viburnum Leaf Beetle remains late winter to early spring. Be sure that temperature is above freezing and buds haven't yet swelled. Its applications often suffocate the insects and eggs that might be overwintering in the nesting places such as crevices, and under the twigs.
Mix 3 ounces of dormant oil in one gallon of water and spray over the entire viburnum plant.
Safer-Insect Killer is an excellent combination of Pyrethrins, Potassium Salts of Fatty Acid, and Neem extracts, and these ingredients are environmentally friendly and kill Viburnum Leaf Beetles in both adult and larval stages. The Pyrethrins application disrupts the nervous system, Potassium Salts of fatty acid cause swift dehydration, whereas, Neem extracts reduce reproduction abilities. The overall combination remains effective during all stages of insect growth and reproduction. It clears the field from Viburnum beetles in one or two applications. The product is OMRI listed and the first choice of organic growers irrespective of the growing culture.
It comes in a ready-to-use formulation. Open the lock, point towards the foliage, and pull the trigger.
It contains a 0.5% mixture of Spinosad A and Spinosad D. It is also OMRI listed and approved for organic gardening. However, some researchers still have reservations about the residual effects of Spinosad on the environment and the edibles. Anyhow, it's a very fast-acting formula that kills the Viburnum Beetle larvae and adults soon after application. This newest product chemistry works well against all crawling, sucking, and chewing types of insects that damage your Viburnum or edible plants.
Mix 2 ounces of the product concentrate per gallon of water and apply over the foliage of the plants.
Systemic Insect Control contains 0.22% Imidacloprid which, is a highly toxic product with prolonged residual effects and is dangerous for honeybees, fish, pollinators, and beneficial insects. The gardeners can use it only on non-edibles and ornamental plants. It requires mixing the product granules in topsoil and watering afterward, immediately. It absorbs by the plant tissues, and the active feeding stops for the next 8-weeks.
Imidacloprid is effective against a variety of insects that feed on the foliage of the plants.
Check out our other guides on common garden bugs.
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