Table 6.
Multiple regression analysis for rootworm abundance and root injury, with field type and management metrics as possible independent variables
| Dependent variable | Parameters | Slope | SE | F | P | Model r2 |
|---|---|---|---|---|---|---|
| Rootworm abundance (square root) | Cry34/35Ab1 + Cry3 (year of sampling)a | 0.56 | 0.31 | 3.25 | 0.08 | 0.23 |
| Proportion years corn (6 yr)b | 1.47 | 0.69 | 4.58 | 0.04 | ||
| Intercept | −0.69 | 0.60 | 1.30 | 0.26 | ||
| Root injury (square root) | Year cont. corn (log)c | 0.06 | 0.04 | 2.60 | 0.12 | 0.25 |
| Soil insecticide used | −0.20 | 0.09 | 4.64 | 0.04 | ||
| Cry3 corn growne | −0.20 | 0.12 | 2.71 | 0.11 | ||
| Intercept | 0.32 | 0.06 | 32.96 | <0.0001 |
aUse of Cry34/35Ab1 + Cry3Bb1 or Cry34/35Ab1 + mCry3A corn in the year the field was sampled (0 = no, 1 = yes).
bProportion of years corn had been grown out of the previous 6 yr.
cNumber of years fields have been planted to corn continuously since 2003.
dVariable represents variation in response due to soil insecticide use in the year of sampling, proportion of years soil insecticide was used in 6 yr, and proportion of years soil insecticide was used on Bt corn due to collinearity among variables.
eVariable represents variation in response due to Cry3 corn grown in the year of sampling and proportion of years Cry3 corn had been grown in the last 6 yr due to collinearity among variables.