* Fiber down for 9th straight session in longest rout since May

* Spot prices on pace for largest monthly loss in over a year

* Nearby price discount widens under pressure from inventories, fund rolls

* Traders eye delayed U.S. government export data due Thursday

NEW YORK, Oct 30 (Reuters) - Cotton futures closed lower on Wednesday for a ninth straight session, marking the longest rout since May as investor liquidation and index fund contract rolling weighed on prices.

The most-active December cotton contract on ICE Futures U.S. closed down 0.5 cent, or 0.6 percent, to settle at 77.84 cents a lb, after easing to a nine-month low of 77.68 cents earlier in the session.

Cotton continued to slump in the face of harvest pressure and contract rolls, said Jobe Moss, a broker with MCM Inc. in Lubbock, Texas.

"There's a little bit of buying under the market, but it can't stop this technical picture, and the crops are bigger than what people were expecting. There's just too much cotton," Moss said.

The crop harvest is underway in key growing regions. Recent data showed the U.S. crop is expected to be healthier than previously thought, and No. 2 producer India is expected to reap a bumper crop this year.

With a close below the key level of 78 cents seen as a technically bearish sign, traders said they were now eyeing 75.50 cents as the next support level.

Recent data has reignited worries over waning demand and another year of surplus.

The U.S. government was scheduled to release weekly export data for the weeks ending Oct. 10, Oct. 17, and Oct. 24 On Thursday.

Delayed U.S. government data for the week of Oct. 15 showed on Wednesday that speculators had trimmed their bullish bets in cotton futures and options for a second straight week.

The most recent ICE data show certified stocks topped 141,000 bales as of Tuesday as they continued to climb to the highest levels since July.

The discount of spot prices to second-month March contracts widened to 1.99 cents a lb from 1.81 cents previously, as fund rolling and the climbing inventories weighed heavily on nearby prices.

Fiber was on pace to end the month down about 9.6 percent, its worst monthly on a spot basis in over a year.

"There's been a complete change in psychology," said a U.S. cotton broker.