Cherry tree borers
Pyrethrin based bark spray has been recommended for borers (I have sap at the base of the tree). I can only find Pyrethrin based garden sprays. Would these be suitable for spraying cherry tree bark? Also, when is the proper time to spray, fall or spring?
As we say in the horticulture business, "the label is the law". If the label of the product you found allows cherry tree spraying, or general garden use on fruit trees, then you can use it and it should be suitable for a bark infestation. If this use is not listed on the label (for example, the spray is only for vegetables), then you can't use it on cherries. In the second case, perhaps the person who recommended the bark spray could suggest a place to find the suitable product.