Location of western corn rootworm populations tested in plant-based bioassays.

<p>The map represents the state of Iowa, USA and individual sections of the map are counties in Iowa. Symbols represent individual fields that were sampled for adult western corn rootworm and subsequently tested in bioassays. Field locations are accurate to the level of an individual county. CPF = current problem field, PPF = past problem field, RMF = rotated maize field, and CMF = continuous maize field.</p

Analysis of variance for data from plant-based bioassays.

<p>Analysis of variance for data from plant-based bioassays.</p

Proportion of third instar larvae on Cry3Bb1 maize and non-Bt maize¹.

<p>Proportion of third instar larvae on Cry3Bb1 maize and non-Bt maize<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0200156#t002fn001" target="_blank">¹</a>.</p

Relations between diet-based and plant-based bioassays for western corn rootworm.

<p>Horizontal lines represent 95% fiducial limits on LC₅₀ values and vertical lines represent the standard error of mean for corrected larval survivorship on Cry3Bb1 maize. Individual points represent samples means. Lables by individual data points represent the follwing: CPF = current problem field, PPF = past problem field, RMF = rotated maize field, CMF = continuous maize field, and CTRL = control population.</p

Survival of western corn rootworm larvae on Cry3Bb1 maize and non-Bt maize in plant-based bioassays.

<p>Bar heights are sample means and error bars are the standard error of the mean. Uppercase letters indicate significant differences between population classes on non-Bt maize and lowercase letters indicate significant differences between population classes on Cry3Bb1 maize. Differences between Cry3Bb1 maize and non-Bt maize within a population class are indicated by either NS for a non-significant difference or Sig., which stands for a significant difference.</p

Sampling date in 2009, corrected survival in bioassays, and history of planting in problem fields (P1–P4) and control fields (C1–C5) from 2003 to 2009.

a<p>Field history indicates the crop that was planted in a field each year: 1 = soybean, 2 = maize lacking rootworm active Bt, 3 = Cry3Bb1 maize, 4 = Cry34/35Ab1 maize, 5 = combination of Cry3Bb1 maize and Cry34/35Ab1 maize, 6 = research plots with non-Bt maize and several Bt maize hybrids (mCry3A <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022629#pone.0022629-Walters1" target="_blank">[46]</a>, Cry3Bb1, and Cry34/35Ab1).</p

Survival of western corn rootworm on Bt and non-Bt maize.

<p>Data are shown for A) Cry3Bb1 maize and B) Cry34/35Ab1 maize. In both cases, survival also is shown for a non-Bt near isogenic hybrid. Bar heights are means and error bars are the standard error of the mean.</p

Correlation analysis for corrected survival of western corn rootworm.

<p>Correlations are shown for A) survival on Cry3Bb1 maize and Cry34/35Ab1 maize and B) survival on Cry3Bb1 maize and number of years Cry3Bb1 maize was planted in a field. Symbols in the graphs correspond to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022629#pone-0022629-t001" target="_blank">Table 1</a>, which lists corrected survival for populations on Bt maize and the cultivation history of fields. For (A), no significant correlation was present between survival on Cry3Bb1 maize and Cry34/35Ab1 maize (r = 0.068; df = 6; P = 0.87). For (B), a significant positive correlation was present between corrected survival on Cry3Bb1 maize and the number of years Cry3Bb1 maize had been grown in a field (r = 0.832; df = 7; P = 0.005).</p

Distribution of sites sampled within Iowa during 2009.

<p>Sites beginning with C are control fields and were not associated with feeding injury to Bt maize, and sites beginning with P were problem fields, which were associated with farmer complaints of severe injury to Cry3Bb1 maize by corn rootworm. Codes correspond to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0022629#pone-0022629-t001" target="_blank">Table 1</a> where a field history is provided along with the corrected survival for these populations of western corn rootworm on Cry3Bb1 maize and Cry34/35Ab1 maize.</p