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Table 1 The percentages and number exceeding the action threshold for each cotton bollworm generation from 2008 to 2015

From: Efficiency of cotton bollworm (Helicoverpa armigera Hübner) control of different Bt cotton varieties in North China

Year Number of varieties 2nd generation (> 10 larvae)a 3rd generation (> 13 larvae)b 4th generation (> 13 larvae)c Ratiosd per generation/%
2nd 3rd 4th
2008 35 0 1 2 0.0 2.9 5.7
2009 29 5 3 2 17.2 10.3 6.9
2010 22 0 1 0 0.0 4.5 0.0
2011 22 9 0 0 40.9 0.0 0.0
2012 21 1 0 0 4.8 0.0 0.0
2013 21 1 0 0 4.8 0.0 0.0
2014 23 2 3 1 8.7 13.0 4.3
2015 24 2 0 0 8.3 0.0 0.0
  1. a2nd (>10 larvae), the number of varieties that exceeded the 10-larvae per 100 cotton plants action threshold at the second generation of cotton bollworms
  2. b3rd (>13 larvae), the number of varieties that exceeded the 13-larvae per 100 cotton plants action threshold at the third generation of cotton bollworms
  3. c4th (> 13 larvae), the number of varieties that exceeded the 13-larvae per 100 cotton plants action threshold at the fourth generation of cotton bollworms
  4. d \( \mathrm{Ratio}\left(\%\right)=\frac{\mathbf{2nd}\kern0.5em \left(>10\ larvae\right),\mathbf{3}\mathbf{rd}\ \left(>13\ larvae\right),\mathbf{or}\ \mathbf{4}\mathbf{th}\ \left(>13\ larvae\right)\ \mathbf{generation}}{\mathbf{Number}\ \mathbf{of}\ \mathbf{varieties}}\times 100 \)