Viburnum Beetle, Viburnum Leaf Beetle, Guelder-Rose Leaf Beetle
Pyrrhalta viburni is a beetle (family: Chrysomelidae), widely known as the Viburnum Leaf Beetle. Viburnum Leaf Beetles are destructive pests because both the adults and larvae will devour the foliage of plants, stripping leaves completely. It's not all doom and gloom if you possess Viburnum in your garden because Viburnum Beetles have a range of natural enemies to help keep them at bay. Some variations of Viburnum which are more resilient to leaf beetle damage, too. V. bodnantense, dawn viburnum, V. carlesii, V. davidii*, David viburnum, V. x juddii, Judd viburnum and V. plicatum are just a handful of some of the more resistant strains. Records of these beetles exist in New York, Maine, Pennsylvania, Vermont and Ohio.
Both adult and larvae damage the leaves of Viburnum.
Eaten by a range of garden animals and insects.
Adults: The adults are greyish-golden brown possessing long antennae, measuring just under 1cm. They're frequently seen copulating on plants. Larvae: The larvae are grub-like, normally sticking to the undersides of leaves as they graze the leaf surface. They look like creamy yellow grubs with black legs and heads, covered in black spots. Eggs: The eggs are laid inside twigs of Viburnum and sealed off with chewed wood and droppings, so they are seldom seen by gardeners.
Leaves can be skeletonised Irregular holes cover the leaves Brown beetles resting or mating on Viburnum Grub-like larvae with black legs found under leaves Tiny lumps and bumps on Viburnum branches where eggs have been laid
Europe and the British Isles; North America
Ladybirds will eat Viburnum beetle larvae. Encourage Ladybirds into the garden by creating bug hotels for them to live in, near to Viburnum plants. Log piles, climbers, hanging baskets and flower patches make good refuges for natural enemies. They're also predated by spined-solider beetles, jumping spiders, lacewing and hoverfly larvae. Random checks beneath leaves are encouraged. Hand removal and dispose of Viburnum beetle larvae, if it is only a small number. If a large infestation of Viburnum beetle larvae, then the plant may have to be left and after the attack, feed and water to encourage recovery and new growth. An adult Viburnum plant should survive an attack even if near total defoliation has occurred. Check current years stems in early winter for egg-laying sites. Small round marks, flat or slightly domed 2mm to 3mm in size are capped egg sites and prune out and dispose of. It's been proposed that using tanglefoot at the base of trees may act as a barrier, preventing larvae reaching the soil to pupate. Horticultural oils are proposed to interrupt egg hatching, however, may scold trees in bright light. Pyrethrin-containing organic pesticides can be used, but are only effective against the larvae. Should never be used if flowers are present.
Insecticides to control Leaf Beetle can target beneficial insects too. Insecticidal soaps or organic pesticides may be more suitable. Check availability with your local Garden Centre.