It's difficult to reproduce the example when you have to go through hoops to get the source data.
My first suggestions is the use the C50 package. It is an updated version of Quinlan's algorithm that doesn't use Java.
Suggestions #2: Change the formula to remove the data frame name and use two back-ticks (you code had a quote character and a back-tick character).
tree1 <- J48(`Stn Code` ~ ., data = delhi1)