Secateurs can appear blunt due to sap that as collected, so regular cleaning will help. Cleaning after cutting diseased material away will prevent the spread to healthy plants.
There are many sharpening tools on the market that can be used on secateurs when they do become blunt. Bypass secateurs have a smaller, often thinner blade and this is the one to sharpen. The anvil type requires the top blade sharpening only. Where chips on the blade are apparent it is perhaps time to consider a blade change on some of the expensive secateurs or buying a new pair.
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