The S&P/ASX 200 Index (ASX: XJO) has followed Wall Street's lead and dropped into the red. At the time of writing, the benchmark index is down 0.9% to 8,123.8 points.

Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

Coles Group Ltd (ASX: COL)

The Coles Group share price is down over 3% to $19.14. This has been driven by the supermarket giant's shares going ex-dividend this morning. When this happens, it means the rights to an upcoming dividend are settled. As a result, new buyers of Coles' shares will not be entitled to this dividend and its share price has dropped to reflect this. Last month, Coles released its half year results and declared a fully franked 37 cents per share interim dividend. It will be paid to eligible shareholders later this month on 27 March.

Ioneer Ltd (ASX: INR)

The Ioneer share price is down 3.5% to 14 cents. This morning, this emerging lithium–boron producer released an update on the Rhyolite Ridge project. According to the release, recent drilling activities have led to a 45% increase in the mineral resource estimate for the lithium-boron project in Nevada, USA. This estimate includes new data from twelve drill holes completed in 2024. It seems that the market may have been looking for a larger increase. Nevertheless, the company's managing director, Bernard Rowe, was pleased with the news. He said: "Today's updated Resource reinforces the remarkable flexibility of Rhyolite Ridge's unique mineralogy. It allows Ioneer to match prevailing market conditions and blend our ore to produce a valuable boric acid coproduct, whose market is separate from the Project's primary lithium product. No other lithium project has this flexibility and economic advantage. In times of low lithium pricing as exists today, the Company can prioritize the high-boron ore over the low-boron ore to optimize the relative proportion of total revenue derived from boron."

Treasury Wine Estates Ltd (ASX: TWE)

The Treasury Wine share price is down 4.5% to $10.10. Like Coles, this has been driven by the wine giant's shares going ex-dividend this morning for its latest dividend. The Penfolds owner released its half year results last month and declared a partially franked 20 cents per share interim dividend. It will be paying this dividend to eligible shareholders on 2 April.

Woolworths Group Ltd (ASX: WOW)

The Woolworths share price is down almost 3% to $29.09. This is another ASX share that has gone ex-dividend today and is falling in response. Last month, Australia's largest supermarket chain released its half year results and declared a fully franked interim dividend of 39 cents per share. This is due to be paid to eligible shareholders next month on 23 April.