| Insect defoliation of soybean Glycine max L. during flowering and pod fill reduces leaf area, delays maturity, and reduces yield. Scouting for insect damage in large fields is time-consuming and costly. Alternate methods are needed to reduce scouting time and costs. The objective of this study is to evaluate the use of aerial imagery in diagnosing damage caused by grasshopper, Melanoplus spp., and bean leaf beetle, Ceratoma trifurcata Forster, during vegetative, flowering, and pod fill stages. Five simulated defoliation treatments were compared, ranging from no defoliation to complete defoliation. Leaf area was obtained from whole plants harvested from the field. Aerial and radiometer images were collected on different dates. Artificial defoliation of 38%--90% was detectable in the aerial images. Yield results were influenced by the extent and timing of damage. The largest yield reduction (27.45%) in 2000 occurred with defoliation at pod fill. Other yield losses were 17.75% at 90% defoliation and 8% at 45% defoliation at flowering. (Abstract shortened by UMI.)... |
