U.S. wholesale prices posted the biggest gain in July since February after a slight increase in June, as drought pushed up food prices, the Labor Department reported Tuesday.

The Producer Price Index (PPI), which measures price changes at factory gates, increased by 0.3 percent in July on a seasonally adjusted basis. The PPI ticked up 0.1 percent in June.

Energy prices edged down 0.4 percent in July, the fifth straight monthly decline, while food costs rose 0.5 percent, the same pace as the previous month.

Corn prices surged 34.5 percent in July from the previous month, and wheat prices jumped 20.2 last month on the back of the United States' worst drought in more than five decades.

Excluding the volatile food and energy sectors, the so-called "core" wholesale prices rose 0.4 percent in July from the previous month, the largest gain since January.

Wholesale prices rose 0.5 percent over the past 12 months ending July.