DefoliationPro: A new training tool for improving the accuracy and precision of defoliation ratings

Defoliation ratings are used to measure the amount of injury that herbivorous insects cause to the leaf tissue of agricultural plants. Defoliation ratings are subjective to the training of the individual conducting the ratings, and often suffer from low intra-rater repeatability. Implementing a standardized visual training method can reduce this source of error. To determine if intra-rater repeatability could be reduced we conducted individual comparisons of pre- and post-training defoliation ratings using the software DefoliationPro. Each of the six individuals took a 30 leaf pre-training test to determine his or her initial accuracy and precision for defoliation ratings. The individuals then took a 30 leaf-training test where the actual percentage of defoliation was presented for each leaf. After the training, the individuals then took a 30 leaf post-training test to determine if their accuracy and precision for defoliation ratings increased. The pre-training defoliation ratings were less accurate and precise than the post-training ratings for each of the six individuals as determined by an increased percentage of the actual severity explained by the estimated severity. The results indicate that DefoliationPro is an effective tool to increase the accuracy and precision of individual defoliation ratings. The use of DefoliationPro could improve the accuracy and precision of data collection in field trials leading to more efficient use of time and space resources.