The 30-year old goal machine has 19 of Killie's 40 league tallies this season with Rory McKenzie the next highest on just four.
Johnston, whose side sits eighth on the Scottish Premiership, praised McKenzie for his goal in the weekend's 2-1 victory at Motherwell but wants more help for he and Rugby Park hero Boyd.
"It can't just be Kris scoring all the goals. Rory McKenzie has done that for us a little bit this season, doing well from that wide role out on the right, using his pace to get in behind teams," said Johnston ahead of Saturday's home clash with St Johnstone.
"He is a real threat when he plays like that and you saw that with his goal against Motherwell last Saturday.
"But we can't rely on just one player like Kris to score the majority of our goals. It's great that we have got someone of his quality. However, we need everyone to chip in.
"We do have players capable of scoring goals if they get into the right areas."
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