Wolf Trap Farm Park, which scrambled to assemble a temporary structure after a fire devastated the Filene Center in April, is averaging sales of only 44 percent of capacity, general director Edward Corn said yesterday.

The figures are lower than projected, and Wolf Trap officials are reexamining their promotion, advertising and marketing strategies. Last year at this time, Wolf Trap averaged a 62 percent attendance rate, although facilities and ticket prices have changed.

" 'Worried' is not the adjective I would use," Corn said of Wolf Trap's response to the attendance figures, which cover a little more than a third of the season. "Certainly, we're concerned. We're always going to be concerned if we're under projected figures."

Corn would not predict whether total summer ticket sales will be less than the $4 million Wolf Trap hopes to pull in for the entire season. There have been 26 performances so far, and another 42 are to come.

"There's certainly the possibility that we can pick up," said Corn. "We've got some very attractive shows coming up." In fact, Corn expects the attendance percentage to go up considerably this week because the Wolf Trap schedule includes several popular performers: Roy Clark, the Righteous Brothers and Lena Horne, whose Sunday night show is already sold out and whose Monday night show is nearly sold out.

Corn cited several factors in the low attendance: traditionally slow June sales, the economy, the publicity about the fire ("Amazingly, people don't realize we're still in business") and pricing and seating arrangements in the new Meadow Center.

"Until people come out and try it, there's still that uncertainty," said Corn. "Is it comfortable? Can you hear? Can you see?"

In the original Filene Center, seats were reserved and ticket prices varied according to sections. In the new Meadow Center, ticket prices are all the same at each show (although prices vary from show to show) and there is no reserved seating. "I don't think there's any question that those are two contributing factors," said Corn. "It doesn't make us happy. We would like to have had different prices and reserved seating. In fact, in retrospect, we probably should have had reserved seating. But at the time, there was no way to do it. We weren't even sure what the seating would look like. We were operating two months after the fire."

Although there are no figures breaking down percentage attendance on the lawn and in the Meadow Center, Corn said attendance on the lawn is "somewhat better."

Another possible reason for low attendance, according to Corn, is that people appear to be selectively attending shows at Wolf Trap, probably for financial reasons. "People are not just coming for entertainment," he said. "They're picking very carefully what they want to see. It's the only way to account for these radical shifts from completely sold out to small attendance. I'm sure in the past, people came to Wolf Trap once a week just to see something."

Corn warned that last year's attendance figures can't be compared fairly with this year's. "It's apples and oranges," he said. This year, as in the last year, 6,500 tickets are available per show. But last year, the Filene Center provided 3,500 seats, while 3,000 spaces were available on the lawn. This year, the Meadow Center provides 2,000 seats and 4,500 are on the lawn.

Wolf Trap is in the process of raising half the money it will take to rebuild the Filene Center. The other half of the estimated $17 million cost is being paid by the government. But in addition, the Wolf Trap Foundation is raising $2 million for the annual operating budget that it would have needed to raise even if there had been no fire.