* Whitehaven Coal top gainer with 12% jump

* Afterpay among top pct losers

* All major sub-indexes down for day

July 14 (Reuters) - Australian shares fell on Tuesday as a growing number of new coronavirus cases in the country's most populous state fanned fears of a second wave of infections.

The S&P/ASX 200 index fell 0.9% to 5,924.6 by 1236 GMT, erasing most of Monday's 1% gain.

New South Wales reported on Monday 14 new cases of COVID-19 at a pub used by freight drivers, right on the heels of a surge in infections in the neighbouring Victoria state, which went back into lockdown last week.

All major sub-indexes were down for the day, with technology stocks leading the decline. The tech sub-index dropped 2.7%, tracking a fall in U.S. peers led by titans including Amazon and Microsoft.

Buy-now-pay-later firm Afterpay Ltd was among the top percentage losers on the benchmark index with a drop of almost 5%.

The gold sub-index fell 2.5%, led by a 6.3% drop in Dacian Gold Ltd, while Alacer Gold Corp lost 5.6%.

Among top performers, Whitehaven Coal jumped about 12%, making it the biggest percentage gainer on the benchmark, after the company posted a 29% jump in quarterly coal production.

Whitehaven Coal shares were also the most heavily traded by volume, with more than 6 million shares changing hands, about six times the 30-day average.

In other news, Westpac Banking Corp, Australia's second-largest lender, named Michael Rowland as its chief financial officer, six months after facing a major money-laundering scandal.

Across the Tasman Sea, New Zealand's benchmark S&P/NZX 50 index inched up 0.03% to 11,438.36.

The top percentage loser on the benchmark index was Pushpay Holdings with a drop of 9%, while the top gainer was Investore Property, up 3.2%. (Reporting by Arundhati Dutta in Bengaluru; Editing by Subhranshu Sahu)