Apple (NASDAQ: AAPL) shares took a hit today following a downgrade to sell by BGC analyst Colin Gillis.

He joined the "Halftime Report" to explain why he thinks it's time to ditch the Cupertino-based company.

Gillis' primary reason for downgrading Apple – and slashing his price target to $85 from $110 – is growing concerns over slowing iPhone sales.

"If you look at the back half of the year, we are not enthusiastic about the next iPhone upgrade cycle; in fact, we've already seen that the 6s upgrade cycle has been slower than the 6, and we think that you're going to see a continued slowdown when the next iPhone hits," he said.

Gillis also believes the tech giant should diversify revenues and make bigger acquisitions.

"You're looking at a management team that has not diversified revenues away. In five years the only product category they've opened up is the watch, and that hasn't had material impact on their revenue. They've squandered their domestic cash buying back stock," argued Gillis.

Apple is down 8% year to date.

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