Fig. 2From: Efficiency of cotton bollworm (Helicoverpa armigera Hübner) control of different Bt cotton varieties in North ChinaThe changes in the number of cotton bollworms and the ratios of damaged cotton stem-tips, buds, and bolls. a to c Changes in the number of cotton bollworms found at the second, third and fourth cotton bollworm generation stages from 2008 to 2015; d to f The ratios of damaged cotton stem-tips, buds, and bolls from 2008 to 2015. The error bars are SEsBack to article page