My young plum tree (4 years) has large sap blobs and mangled new growth leaves, in very regular spots - at the crotch of each new growth & branch. I assume this is a fungal disease because the ugly gray of the leaves? But I also start to think maybe borers because it's so methodical, as if at each sheltered area where a larvae entered? Any suggestions on treatment? There are a number of these little insects under almost every leaf, but they don't look like the pics of peach borers I see online. Thanks