I have had many reports of corn leaf aphids over the last couple of weeks, including several in pre-tassel corn. Corn leaf aphids are usually found inside of the upper whorl (unlike other species which are primarily found on the undersides of leaves), and are darker in color than other species we see in corn. This year, the wide variety of planting dates has resulted in corn that is all over the place in terms of stage – these aphids are particularly a problem if they are present in large numbers during pollination. (Fortunately, where we have adequate moisture and cool temperatures during pollination, this effect will be minimized). Consider an insecticide if 50% of plants have aphid colonies (~50-100 aphids) prior to or during R1. Once pollination has passed, it takes much greater numbers to cause yield loss.