Barlettg pear espalier

I have a Bartlet Pear espalier that flowered beautifully this spring, but has now developed holey leaves.The local nursery recommended a fruit and shrub spray which I used. The leaves under close inspection seemed to have tiny black specks all over them that when sprayed kind of turned to mush.The tree is loaded with fruit which looks nice and healthy. I don,t know if the culprit is an insect or a disease. Can anyone help?

 

I think that it could be a pear slug. I have had this in the past and I think that's what it was.