Average tea prices in India, the world's second-biggest producer, plunged at last week's auction on sluggish demand and rising supplies of poor quality leaf. The CTC (crush-tear-curl) grade leaf was sold at 109.07 rupees ($1.75) per kg last week, down 9.5 percent from the previous auction, while prices of the dust grade plunged 8 percent to 113.48 rupees per kg.