The caterpillar of the magpie moth are quite at home eating either gooseberries or currant - black or red.
The caterpillar is easy to recognise because of its bright colouring, and also the way it arches its back as it crawls along the leaf stems. This characteristic of humping along is called looping, and there are several caterpillars referred to as looping caterpillars.
The larvae of the Magpie moth are not considered to be too much of a nuisance - other than a little defoliating. However, they should be picked off the Gooseberry, blackcurrant or redcurrant as soon as seen.
Chemical sprays are not normally necessary unless there is a heavy infestation of the caterpillars. If this is so, then a spray with Bifenthrin - a contact insecticide, will bring them under control. This is best done before the flowers are open, or after petal drop. This prevents any accidental damage to friendly pollinating insects.
The species has undergone a decline in population over the last 10 years - now just 42% of previous population. Maybe with that in mind, then the hand picking of the caterpillars rather than the 'kill 'em all' attitude will do a little to help.
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