ABANKROM, Ghana — Yaa Amekudzi bounces along dirt roads in a sport-utility vehicle from one village to the next as part of a $1 billion scramble by the world’s top chocolate makers to fix the industry’s most vexing problem.

Demand for chocolate is stronger than ever, especially now that more consumers in China and India are buying bars and bonbons long considered an unaffordable luxury. But cocoa production is down, including a steep slide last year in Ghana, the second-largest cocoa-growing country. Cocoa prices have jumped nearly 40% since the start of 2012.