Loans to developing nations by the International Monetary Fund dropped dramatically in the year ended April 30, falling to $6 billion from about $10 billion in each of the two preceding years, the agency said yesterday in its annual report.

The decline was attributed to recovery in global activity, "coupled with the success of adjustment policies" in Third World countries -- that is, their efforts to control budget deficits and other economic excesses.

On policy issues, the report broke no new ground.

But it stressed that three "sobering" elements still were present in the Third World outlook and repeated the agency's concerns that European countries, still facing high unemployment, have not successfully grappled with excessive wage rates and inflexible union rules.

The report also devoted considerable attention to the worldwide dangers of protectionism and the agency's inability, through "surveillance" procedures, to get key members to follow guidelines that would be "advocated by the fund membership collectively."

The three worrisome aspects of the Third World situation cited in the report are, first, the fact that economic growth remains below the long-term trend, even among countries that have responded well to IMF supervision; second, the remaining heavy debt burdens; and third, the fact that developing countries haven't matched the success of the richer ones in controlling prices.

On the question of the IMF's paper money, Special Drawing Rights, the report indicated that, despite general support for a new issue of SDRs among many member nations and in the IMF staff, opposition by the United States makes it highly unlikely that favorable action will be taken at the agency's annual meeting next month in Seoul.

The World Bank also announced last week that its lending had dropped, from $12 billion in its fiscal year 1984 to $11.4 billion in 1985. But in contrast to the bank's projection that its lending will rise over this and the next few years, a key official told Tbe Washington Post that "IMF lending will continue to decline, although not very sharply, over the next two or three years."

Officials said that the prospective decline represented a normal phasing down of IMF operations, which reached a peak in the 1983-84 response to the debt crisis that was touched off in 1982. IMF programs are designed to deal with short-term and medium-term needs, and expectations are that the World Bank will be stepping up its loans, concentrating on longer-term needs for growth in Third World economies.

According to the annual report, the number of IMF borrowing arrangements in effect at the end of April stood at 30, down five from the year before, while commitments for new loans dropped from $19 billion to $12 billion. Total loans outstanding among 83 borrowers amount to $35 billion, equal to 39 percent of quota deposits by member countries.

"Despite the improvement in the world economic situation, many member countries continue to face difficult payments problems, as well as serious uncertainties in their medium-term prospects. Consequently, the prospective demand for fund assistance is expected to remain at a high level," the report said.

The fund reported that four countries were in arrears on repayments by $176 million. Two of the four, Vietnam and Guyana, have been declared ineligible to borrow further from the fund, joining Cambodia in that status. Officials would not name the fourth country, which has not yet been declared ineligible.

The report noted that economic recovery in Europe was disappointing, behind the pace in Japan as well as the United States, and called on both for better economic performance "as the stimulus imparted by the U.S. economy to the rest of the world tapers off."

In a guarded way, the IMF report urged Japan to make further efforts to open up its markets and abandon some of the traditional trading practices that are perceived as obstacles to imports. "Further efforts in this regard could both benefit Japanese consumers and help fend off some of the proposals now pending in other countries for restrictions against Japanese exports," it said.