Topping of sweet corn a few weeks before harvest is practiced in western Washington state and Nebraska to improve harvesting efficiency. Reports of east coast growers indicate topping may hasten earliness by 2 to 3 days, improve hand picking ease, reduce bird damage, and reduce wind lodging. Another potential advantage would be better spray coverage of the ear to prevent corn borer and earworm damage. Some drawbacks to the practice might include: reduction in earsize and flavor, malformed ears from lack of good pollination,sunburn of exposed ears(particularly late plantings), and additional costs. Generally, topping refers to removing the top of the corn plant just above the ear after pollen shed and pollination of the ear has occurred.
Iowa State University
Taber, Henry G. and Lawson, Vincent, "Sweet Corn ToppingTrial" (2007). Iowa State Research Farm Progress Reports. 877.