* Banks, insurance companies tumble
* Strong yen trend increases exporter earnings worries
By Ayai Tomisawa
TOKYO, Sept 28 (Reuters) - Japan's Nikkei share average fell on Wednesday morning as a strong yen continued to sour sentiment, while ex-dividend share price adjustments pressured the market.
The Nikkei dropped 1.8 percent, or 295.32 points, to 16,388.61 at midmorning trade. About 115-120 points are cut from the Nikkei by the ex-dividend price adjustment, according to market participants.
With the dollar trading below 105 yen for about two months, investors are increasingly worried about Japanese exporters' earnings, traders said.
Most automakers have calculated their earnings forecasts on the assumption that the dollar would trade at 105 yen, and most electronics makers expect the dollar to trade at 110 yen, according to brokerages.
"By looking at the current dollar-yen levels, companies will likely have no choice but to lower their dollar-yen assumptions at their mid-year earnings releases," said Norihiro Fujito, a senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities.
On Wednesday morning, the dollar was at 100.470 yen.
Exporters were lower, with Honda Motor Co, Fuji Heavy Industries and Panasonic Corp all falling 2.1 percent.
Banking stocks and insurers tumbled as the benchmark 10-year JGB yield has stayed negative, hitting institutions sensitive to fixed-income returns.
Mitsubishi UFJ Financial Group stumbled 3.0 percent, Mizuho Financial Group declined 3.9 percent while Dai-ichi Life Insurance shed 3.2 percent.
Traders said banking sector sentiment was also hit by concerns over Deutsche Bank, with investors worried about the impact of a $14 billion fine.
The broader Topix dropped 1.6 percent to 1,327.89 and the JPX-Nikkei Index 400 fell 1.7 percent to 11,884.30.
Reporting by Ayai Tomisawa; Editing by Eric Meijer