@Faygo
Copper needs sprayed pre bloom so pears will not russet. Frost rings are based on variety and bloom time. Copper also kills ice forming bacteria which buys you a few extra degrees of cold tolerance at times. At this point its more about how Kevin is going to avoid this problem next year. Copper is used to retard blossom blast and fireblight. If its rust a fungicide spray retards it. Pear Rust. Another fungicide is used with with scab Apple and Pear Scab Management Guidelines--UC IPM
Typically fungicides are already used such as immunox, captan etc. To control the other host of many pear diseases that are possible Disease Control for Home Pear Orchards. These fungicides do not work well on rust and its best to click the rust link to look at the latest developments on the fight with rust.