🐛✗ Tested and false“Gooseberry sawfly is a gooseberry-only pest and doesn't touch currant bushes.”
Both the RHS and Washington State University's extension service list currants alongside gooseberries as hosts for this pest. The RHS's own redcurrant growing page names gooseberry sawfly directly, and its dedicated pest page adds white currants to the list. The one real exception is blackcurrants: the RHS's blackcurrant growing page does not mention this pest at all, so the myth is only half wrong.
Our read The safer version of this myth would be "gooseberry sawfly skips blackcurrants," which does check out. Treating currants as a category is what breaks it.
What to do: Put redcurrant and white currant bushes on the same twice-weekly check as gooseberries; blackcurrants don't need watching for this particular pest.
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“Hand-picking sawfly larvae doesn't work because they hide low down inside the bush where you can't see them.”
The RHS and Garden Organic both point out exactly where the larvae start out, on the underside of leaves low down in the centre of the bush, and both still recommend hand-picking as a real control once a grower knows to look there. Garden Organic's own monitoring advice is to start the search in the centre of the bush and work outwards, not to scan the outer foliage first.
Our read This myth gets the biology right and the conclusion wrong. Knowing where the larvae hide is what makes hand-picking work, not what defeats it.
What to do: Start every check at the centre of the bush and the underside of the leaves, then work outward, rather than glancing over the outer foliage and assuming the bush is clean.
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- RHS, Gooseberry SawflyFemale sawflies lay eggs on the underside of leaves low down in the centre of the bush, so young larvae go unnoticed until they've eaten their way upwards and outwards.
- Garden Organic, Your Organic Garden in JulyContinue a twice-weekly search for gooseberry sawfly larvae, starting in the centre of the bush and working outwards, and pick off and destroy what you find.
“A bush stripped completely bare by sawfly larvae is dead or as good as dead.”
Plants will usually survive complete defoliation, though that year's yield may be reduced. The bush itself isn't lost, but a stripped bush has fewer resources going into that year's crop.
What to do: Don't dig out a defoliated bush. Focus instead on catching the next generation of larvae early so the same bush doesn't get stripped a second time in one season.
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“Once you've dealt with a gooseberry sawfly outbreak, that's the pest sorted for the season.”
The RHS records up to three generations a year for the common gooseberry sawfly, running from late April through to September, and up to four for the small gooseberry sawfly. Washington State University's extension service tracks a second generation of the same pest appearing around June or July. A bush cleared in May can still face a fresh wave of larvae in high summer and again into early autumn.
What to do: Keep the twice-weekly check running from April through September, not just for as long as it takes to clear the first generation.
In Scotland: A bush that's already been stripped once has less of the growing season left to recover cropping from a second or third generation on top, which is the reasoning behind checking through to September rather than stopping after the first generation is dealt with.
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“A healthy gooseberry bush can go from a few nibbled leaves to completely bare in just a few days once sawfly larvae get going.”
The RHS describes gooseberry sawfly foliage as being rapidly devoured by the caterpillar-like larvae, and Washington State University's extension service separately documents the same pest causing severe defoliation once a population is established on currant and gooseberry leaves. Because the larvae hatch in a cluster low in the bush and feed together, damage that looks minor on one check can be most of the bush by the next.
Our read Neither source puts an exact number of days on it, but the combination of rapid feeding and clustered larvae hatching together is why a bush can look fine one visit and stripped the next.
What to do: Check bushes twice a week from April, starting at the centre of the bush, so a small cluster gets picked off before it becomes a stripped bush.
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