Impact on Heroin Influx Unknown : U.S. Says Mexico Has Bettered Efforts to Destroy Drug Crops

Mexico’s drug crop-destruction program has improved, but it is too early to tell whether the country will make substantial strides this year toward erasing its record as the No. 1 source of U.S. heroin, the head of the State Department’s anti-narcotics drive said Thursday.

In recent weeks the U.S. Drug Enforcement Administration has verified that Mexico sprayed herbicides on 99% of the opium fields that it told U.S. authorities it would spray during the current campaign, said Ann Wrobleski, assistant secretary of state for international narcotics matters.

Wrobleski said that in previous years Mexico would promise to spray a certain number of fields, but spot checks by the U.S. agents would show that only 20% of the fields on the Mexican list had actually been sprayed.

She said the Mexicans also are using a more efficient herbicide mixture to kill opium, the raw ingredient in heroin.

Nevertheless, it is too early even for preliminary estimates of how much opium Mexico will produce this year, since the harvest has just begun, Wrobleski said.

The State Department, meanwhile, in its semiannual report on foreign anti-drug efforts made no changes in its preliminary assessment last February that Mexico in 1985 was “once again the largest single-country source of heroin and marijuana imported into the United States.”

Mexico produced up to 45 metric tons of opium and up to 4,000 tons of marijuana last year, and cocaine shipments from South America through Mexico to the United States increased, the report said.

The report follows the approval by Congress last week of an anti-drug bill that, when signed into law by President Reagan, will automatically suspend half the foreign aid to every drug-producing country for the current fiscal year.