Counting dropped ears is a good way to measure hybrid ear retention and tolerance to European corn borers. Check overall plant and ear height as well as husk conditions. Hybrids with husks that loosen as ears mature generally dry down rapidly. Check for goose-necked stalks. This is often root pruning caused by corn rootworms.
Hybrids differ in their ability to regrow pruned roots.
Be careful with test plots consisting predominately of one company's hybrids. Don't put much stock in results from one location and one year, even if the trial is well-run and reliable. Years differ and the results from other locations may more closely match next year. Don't over emphasize results from one type of trial. Use data and observations from university trials, local demonstration plots, and then your own on-farm trials to look for consistent trends.