The arrival of Western food parcels in the Soviet Union is a gratifying sign of human solidarity at times of crisis.

It is good that children and old people may get the special food and medicines they need and which the Soviet economy cannot provide; good, too, if Western governmental aid eases hardship (we are not talking of starvation) among the wider population in the coming winter.Unfortunately, though, the crisis also shows how little has been done, five years after the launching of perestroika, to change the suicidal habits of the Soviet economy.

There are old and new causes of the present difficulties, and the old ones are very old indeed. Much of this year's good harvest has been wasted, but that has been a regular story in the Soviet press for decades. Perhaps one-third of what is produced by the farms is lost, destroyed or allowed to rot on its tortuous way to the shops. For many summers, Soviet TV has broadcast pictures of trucks leaving a carpet of grain on the roads as they drive to the storage silos.

Vegetables rotting in cellars; milk turning sour for lack of refrigeration; fruit wasted because there is no machinery to process it or goods wagons to transport it - all have long been regular features of the Soviet agricultural year.

Nor is there anything new about under-the-counter trade in shops and theft throughout the supply system. Was not one of the most notorious criminals of the Brezhnev era the manager of Moscow's most celebrated food shop?

Old flaws have become more deadly as the discipline of the command economy slackens. Such balance as the old Soviet economy did achieve depended on obedience to the commands of the center. Mikhail Gorbachev tried to abolish this, but since the government failed to introduce real prices at the same time, the result was often counterproductive.

Growing conflict between republics and regions, in some cases virtual civil war, has further disrupted trade, and so have political vendettas against reform-minded local governments.

But none of these difficulties disguises the damage done by Gorbachev's slowness in taking the country toward a market economy. Given the continuing absence of a market, it's not surprising that of 122 food production lines imported from the West two years ago, only 18 are yet in operation, or that only 15 percent of the 2,000 registered foreign joint ventures are actually working.

Gorbachev suffers from a particular prejudice about private ownership in general and of land in particular, though the latter is seen by many as vital at a time when Soviet farming has reached breaking point.

Paradoxically, it is the awfulness of the countryside's experience during Stalin's collectivization that has set Gorbachev's heart against private farming. Both his own grandfathers were imprisoned during collectivization, even though one of them was himself an enthusiastic collectivizer.

Because Gorbachev's economic reforms have scarcely gone beyond the lipstick stage, the West's scope to help him in his hour of difficulty and his country's need is limited.