A special task force headed by Agriculture Secretary Richard E. Lyng told President Reagan on Friday the 1988 drought and abnormal heat are the worst on record at this stage of the season and have bitten deeply into harvests of wheat, soybeans, corn and other livestock feed grains.

"While July rains have eased the dry conditions in some parts of the Great Plains and Delta, conditions have worsened in the eastern Corn Belt and Southeast where crops are now in the critical growth stage," the panel said in its second report to the president.Market prices for a number of commodities "are well above spring levels and are highly volatile," the report said. Some livestock producers, faced with rising feed costs, have been forced to liquidate herds.

The report mostly reviewed what has been said before by the Agriculture Department and other agencies, and during President Reagan's tour this week in drought areas of Illinois and Iowa.

Lyng will head a team on a three-day visit next week to 11 drought-stricken states, from Tennesee to the Dakotas.

As USDA had reported earlier, the report noted that 1988 wheat production is down 13 percent from last year, and that the corn crop is expected to decline by 26 percent to 5.2 billion bushels. Soybean output is also projected to drop by 13 percent.

Consumer food prices, the task force reported, are expected to rise an additional 1 percent this year because of the drought, and another 2 percent in 1989. That was in line with previous USDA estimates.

The task force said drought relief legislation has been working its way through Congress and "would provide effective disaster assistance if it advances unencumbered with provisions unrelated to the drought" and meets budgetary and other guidelines.