Prolific Washington novelist Les Whitten has written another thriller that this time takes his character, a retired investigative reporter, into the complex world of the wine industry. Whitten, himself a highly respected investigative reporter, once shared a byline with columnist Jack Anderson. The new book is titled "A Day Without Sunshine" as in "A day without wine is . . ."

Boston Pops conductor John Williams and singer John Denver spent early yesterday practicing in Williams' Watergate Hotel suite before their performance later in the day at the Lincoln Memorial . . . And when astronaut Sally Ride and scientist/media celebrity Carl Sagan checked into their Watergate suites, the hotel sent them Watergate chocolates and Mars candy bars. Most guests don't get Mars bars, but these two are attending the Planetary Society Conference on Mars here . . .

Except for the "Look for the Union Label" television ad, most labor advertising is pretty dull and humorless. The United Food and Commercial Workers International Union is going to try the humorous approach and this week will be introducing actress Vicki Lawrence, star of NBC's "Mama's Family" and formerly of "The Carol Burnett Show." Lawrence will be in town for a showing of her television ads for the union, in which she wears her familiar "Mama's" clothes . . .

Kate Burton visited the grave of her father Richard Burton in Celigny, Switzerland, just before being married Saturday in the Celigny chapel where his funeral service was held nearly a year ago. The 27-year-old daughter of Burton and his first wife Sybil married 25-year-old theater producer Michael Ritchie . . .

Television actor Dan "Grizzly Adams" Haggerty, who has been having his problems lately, suffered a broken leg and a number of cuts and bruises this weekend when he lost control of his motorcycle on a canyon curve in Los Angeles. Haggerty entered a guilty plea last week to tax evasion charges and in March was convicted of selling cocaine to undercover officers . . .

Former Senate majority leader Howard Baker Jr., out on the early campaign circuit at a Republican picnic in Massachusetts Saturday, joked about his presidential plans but made certain everyone knew he was a committed admirer of President Reagan, the man who beat him for the 1980 Republican presidential primary nomination. As for the presidency, the former Tennessee senator wouldn't announce his plans yet, but he did quote his 102-year-old grandmother as advising him to run for county sheriff because "that's where the power is" . . .