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I have a mature Snowball tree (Viburnum opulus) that is stripped of its leaves and severely weakened several times a year by the viburnum beetle. The Royal Horticultural Society recommend several pesticides but, unfortunately, they are all in spray form, and my tree is too tall for me to spray. Can anyone suggest a suitable systemic pesticide that I could apply to the soil around the base of the tree? Many thanks.

Update: Apart from a sprinkling of skeletonized leaves, the tree has escaped the ravages of the dreaded beetle so far (just when I was about to go to war!); I put this down to the prolonged winter freeze-up which must have wiped most of them out - Fingers crossed!

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*NORTH AMERICAN (Check to ensure predatory insects can be introduced in the UK)

There is a pretty good research article from Cornell University. It does not specifically list pesticides that you could place around the base, however, there may be a few other options that you will find suitable.

Such as inducing a predator insect to attack the beetle:

Encourage beneficial insects. Several generalist predators feed on viburnum leaf beetle larvae including lady beetle adults and larvae, lacewing larvae and spined soldier bugs nymphs. The lady beetle adults and spined soldier bug adults also eat adult viburnum leaf beetles. Encourage these and other beneficial insects by avoiding broad-spectrum insecticides and maintaining diverse species of plants for beneficial insect habitat near viburnums. Initial investigations by Cornell researchers on these biological control options also indicate that augmenting natural populations of these predators may dramatically limit viburnum leaf beetle damage. Researcher continues in this area, check back later for more information.

Prevent the larvae from maturing:

Foil larvae. Researchers recently learned that the larvae don't drop from the leaves to the soil to pupate. Instead, they crawl down the tree. While it hasn't yet been tested, it is likely that putting a sticky barrier such as Tanglefoot tree pest barrier around the base of the shrub could keep larvae from reaching the soil to pupate.

Given your situation the other options listed on the site may not be easy to accomplish. These solutions may take time, but in the long run should protect your tree.

(Information directly from link posted above)

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This won't treat your soil, but introducing Ladybirds(we call them ladybugs here) may help per this answer. They are available in the UK as larvae through Amazon in more controlled quantities than they are in the states (where you can buy about 1500 fully grown live ones for that price). However you may be able to find a garden center or local agricultural society that can provide them in better quantities. You can also do things to attract them by planting attractive plants (tulip and Lilly according to this) or putting out ladybug lures though the reviews for these are not entirely positive.

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The only thing that is effective is Diazinon. Hoever it was banned several years ago.I managed to get the last container at HOME HAREWARE three years ago but now I have run out. This stuff works like magic in a very low concentration (one tbsp. to 4l water)Spray as soon as blossoms start to appear then twice more or until no sign of maggot.

  • It probably got banned for a good reason. People who care for the one coming after them tend to avoid chemicals, even if it prevents them to garden some (hill-adapted) plants. – J. Chomel Jul 2 '18 at 8:31

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