Viburnum leaf beetle Pyrrhalta viburni damage (C) photo by Whitney Cranshaw
This is a serious pest of many members of the Viburnum family and is native to Europe and Asia, but has now been identified in many countries around the world. There are thought to be around 250 species of leaf beetle found in Great Britain. Whilst most feed on the foliage of plants, only a few cause serious damage like the Viburnum beetle. Many like the Viburnum beetle are host specific and can only survive on certain species specific host plants.
Symptoms
In spring, Viburnums exhibit symptoms of foliage being eaten between the veins. The edges of eaten foliage is often brown as the grubs feed on different surface areas. This is often in more protected parts of the plant and away from natural predators such as birds. Most commonly seen on Viburnum tinus and a number of deciduous species of Viburnum. This leads to poor, stunted growth and problems seem to get worse each year. It is a major problem in Viburnum hedges and in landscaped area with mass plantings. Where adults are present, some people have reported a foul smell in addition to normal Viburnum odours, this is caused by adult beetles excrement.
Commonly attacked Viburnums include V. tinus. V. opulus and V. lantana plus others.
Life Cycle
The Viburnum beetle completes only one life per year. Males and females mate, and then females go on to lay eggs in late Autumn and winter in holes in twigs they have made by chewing. The female will deposit 5-6 eggs in each hole, usually on the underside of the stem, making them invisible to us and predators. They then cover their eggs with frass which protects the eggs from extremes of weather.
Eggs hatch in May depending on the weather, and after hatching go through several stages as larvae, each stage they become bigger after moulting. The larvae are creamy yellow with distinct black marking, and will vigorously feed on the foliage of the host plant for around a month. They then drop to the soil to pupate amongst soil debris before emerging as adults in June and early July, which are 4.5-6 mm long.
Control
Non Pesticide control
Grow resistant species of Viburnum, in my experience, such as V. carlesii, V. plicatum, and the fragrant V. x juddii. i have noticed these adjacent to the more prone species, which have been completely devastated.
Remove any infected twigs or stems, especially if you can see areas of egg laying, before they hatch.
Regularly inspect susceptible host plants, especially in spring and early summer. Physically crush larvae or remove from the area, tedious, but effect on a smaller scale, but not practical in the wider landscape.
Stir the soil around plants to damage and kill any overwintering adults or larvae.
Pesticide control
A number of pesticides are available capable of control the larvae, especially while at the smaller stages. Chemicals are unlikely to be effective against adults because of their size.
(C) The information below is from the RHS Pesticide List
1. Natural (organic) insecticides
These products are derived from plants or are other naturally occurring substances. They are contact in
action and require thorough application, especially to the undersides of leaves. They can affect a broad range of small invertebrates, including beneficials if they are present at the time of treatment. The short persistence may mean that frequent applications are required. They are considered safe to use on most
plants, including listed fruits and vegetables, these can be treated close to harvest (see label instructions).
a) Natural pyrethrum/pyrethrins
Derived from the flowers of Tanacetum cinerariifolium (syn. Chrysanthemum cinerariifolium). Broad
spectrum insecticide, that can control a wide range of invertebrates including whitefly, small caterpillars,
aphids, thrips, leafhoppers, capsids, ants and some beetles.
Sprays Bug Clear Ultra 2 Gun RTU (also contains vegetable oils)
Bug Clear Ultra 2 concentrate (also contains vegetable oils)
Neudorff Bug Free Bug and Larvae Killer RTU and concentrate (also contains vegetable oils)
Dusts & Py Insect Killer Powder
Granules
b) Fatty acids (insecticidal soaps) For use against aphids, whitefly, thrips, mealy bugs, scale insects, leafhoppers and red spider mite.
Sprays Doff Greenfly and Blackfly Bug Killer RTU
Doff Universal Bug Killer RTU
c) Plant oils and extracts
Refined plant oils, such as those derived from rape seed and sunflower, which block the breathing pores
(spiracles) of small insects and mites, including aphids, whitefly, thrips, mealy bugs, scale insects and red spider mite. Larger invertebrates such as bees and ladybirds are less likely to be harmed. No harvest interval required, but do not use on fuchsia or begonia. Also, available as winter wash for use against overwintering aphid eggs on dormant deciduous fruit trees and bushes.
Sprays Growing Success Winter Tree Wash
Vitax Plant Guard Pest & Disease Control RTU & Concentrate (contains fish oils)
Bug Clear Fruit & Veg Concentrate
2. Compounds with a physical mode of action (not-organic)
Plant invigorators Consisting of blends of surfactants and nutrients or fatty acids and algae extracts, plant invigorators aid
the optimal nutrition of plants and can help control whitefly, aphids, mealy bugs and red spider mite as well as some plant diseases. Healthy plants are more resistant to pests and diseases, and the invigorators give some control by a sticking and a washing process.
Spray Ecofective House Plant Defender 3 in 1 RTU
Ecofective Bug and Mildew Control RTU and concentrate
Ecofective Bug Control
Ecofective Rose Defender 3 in 1 RTU
Growing Success Bug Stop RTU
Growing Success Rose Guard RTU
RHS Bug and Mildew Control RTU and concentrate
SB Plant Invigorator RTU and concentrate
Westland Resolva Natural Power Bug & Mildew
3. Synthetic insecticides: contact action
Synthetic pyrethroids Contact and broad spectrum, effective against a wide range of insects including aphids, whiteflies,
leafhoppers, thrips, beetles, ants and small caterpillars. By making alterations to the molecular structure of natural pyrethrum, synthetic photostable pyrethroid compounds, such as cypermethrin, lambda- cyhalothrin deltamethrin and permethrin, were developed. These synthetic pyrethroids retain the low
mammalian toxicity of other pyrethroids but can remain active against insects for several weeks. Natural pyrethroids break down quickly in sunlight losing their activity within days. Some products can be used on listed food plants.
a) Deltamethrin
A spray concentrate and ready to use for controlling aphids, whitefly, caterpillars, codling moth, plum
moth, tortrix moths, raspberry beetle, flea beetles, weevils, sawfly larvae, apple and pear suckers, leafhoppers, capsid bugs, scale insects and mealybugs on ornamental plants and a wide range of listed edibles.
Sprays
Baby Bio Houseplant Bug Killer RTU
Provanto Ultimate Bug Killer RTU and concentrate
Provanto Ultimate Fruit & Vegetable Bug Killer RTU and concentrate
Provanto Sprayday Greenfly Killer concentrate
Toprose Bug Killer RTU
b) Lambda-cyhalothrin
A concentrate and ready to use spray for controlling aphids, capsid bug, thrips, whitefly, beetles,
caterpillars, pea moth, pea and bean weevil, sawflies, leaf curling midges, carrot fly adults and some
other insects. Can be used on ornamental plants and a wide range of listed fruits and vegetables.
Sprays Westland Resolva Bug Killer RTU and concentrate
c) Cypermethrin
Available as a ready to use spray and concentrate for application to a wide range of ornamental and
edible plants. There is also a ready to use spray for aphid control with a fungicide that is effective
against rose rust, blackspot and powdery mildew that can be used on ornamental plants.
Sprays Py Bug Killer RTU and concentrate
Doff Rose Shield Bug & Fungus Killer RTU (+ myclobutanil*)
Rose Clear Ultra Gun 2 RTU (+ myclobutanil*)
Vitax Rosegarde RTU (+ myclobutanil*)
d) Permethrin
Smoke formulations for use against aphids, whitefly and other insects in greenhouses.
Smoke DeadFast Greenhouse Smoke Generator
DeadFast Greenhouse Smoke Fumigator
The mention of any product, supplier or service does not constitute an endorsement by Howard Drury
I am grateful for the help of the following
Stiga and their work with wikipedia
The Royal horticultural Society and their Pesticide List
Forestry Images for permission to use their images
The information given in this Fact Sheet is provided in good faith. It is however of necessity general information and advice on the topic. Howard Drury will not be under any liability in respect of the provision of such advice and information, and you are strongly advised to seek independent advice on any particular gardening problems or queries you may have, preferably from experts who can (when appropriate) inspect the problem before providing advice.
© 2022. This material has been produced by Howard Drury and must not be reproduced in part or full physically or electronically without the written consent of Howard Drury, Kings Heath, Birmingham, B13 0SJ. The only exception be to print a single copy for personal use from a downloaded file as part of www.thedrurys.com website. Visit www.thedrurys.com or email
JHD//02/04/2022
