National financial markets and tri-county stocks continued to plunge March 16 in defiance of new fiscal stimulus as states imposed new restrictions over the weekend on restaurants, movie theaters and other businesses.

President Donald Trump warned that the economic impact of the coronavirus epidemic could last through the summer. 

The S&P 500 fell 12 percent in the selloff, and the Dow Jones Industrial Average dove 13 percent. The Tri-Counties fared somewhat better, falling 10 percent overall, including a 6.6 percent decline for regional giant Amgen to $188.68 per share.

Atara Biotherapeutics plunged 26 percent, followed by declines of more than 25 percent for financial stocks PennyMac Financial and PennyMac Mortgage. 

Camarillo semiconductor company Semtech fell nearly 23 percent. Regional software firms also saw declines, including a 20 percent drop for Ventura adtech firm The Trade Desk, and a 16 percent fall for Goleta property management software developer AppFolio to a new 52-week low. 

Aerospace and instrumentation stock Teledyne also fell 13 percent, but drone maker AeroVironment rose slightly, ending the day up 1.2 percent to $51.01. 

A few small-cap stocks defied the market plunge, including Goleta electronics maker Resonant, which ended up 6.7 percent, and Camarillo-based Salem Media, which rose 2.8 percent. CDTi Advanced Materials, based in Oxnard, gained 3 cents, a 27 percent gain for the day.

• Contact Marissa Nall at mnall@pacbiztimes.com.