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Sponsored: Do’s and Don’ts At Pollination Time

Seeing tassels emerge from a corn field is an exciting time in each growing season. By this point, you’ve done everything you can to ensure the success of this crop, now you put the rest in the hands of Mother Nature. Corn pollination is the most critical stage of corn development; however, it is often one of the most misunderstood stages in the corn life cycle! 

Weather is the single biggest factor in the success or failure of pollination. It can be too hot or too cold, too wet or too dry. At the VT (tasseling) growth stage, corn has generally achieved its maximum plant height. A hail storm at this stage can reduce yield by up to 100 percent as all the leaves of the corn plant are now visible, making total leaf or tassel loss most severe. Extreme heat, especially temperatures above 100°F degrees, can kill pollen. However, the corn plant has an amazing ability to compensate for this heat stress.

Pollen shed usually happens in the mid-morning and late-afternoon. This happens for a couple of reasons. The anthers on the tassel that contain the pollen won’t open in wet conditions, therefore, they don’t shed pollen on rainy days or while the dew is on in the mornings. After the dew dries off in the mid-morning hours and before the temperatures get too hot, pollen shed will occur. Once the temperature rises, pollen shed will often stop until the temperatures drop again in the late-afternoon or early evening. Prolonged hot and dry conditions will speed up the pollination process, whereas cool and humid conditions will slow it down. The good news is that pollination will typically last anywhere from a few days up to two weeks in a field, hopefully allowing it to occur when the weather is most favorable.

Aside from the weather, nitrogen (N) also plays a large role in the overall success of the corn crop from VT to maturity. At the R1 (silking) growth stage, corn will begin to remobilize N from other plant parts, such as the lower leaves, to the developing grain. By maturity, up to two thirds of the total plant N is contained in the grain. Lack of adequate N at grain fill can cause the lower leaves to “fire” or show N deficiency. A lack of available N can also cause cannibalization of the stalk which can turn into standability and stalk rots at harvest time.

Applications of fungicides and insecticides at the VT growth stage are pretty common today. Insecticides target pests such as corn rootworm beetles or Japanese beetles, which feed on silks and can interfere with pollination. Fungicides target diseases such as gray leaf spot. One thing to keep in mind when applying fungicides at tassel is to always apply it when the field is at full tassel up to brown silk, or the R2 growth stage. The addition of a nonionic surfactant (NIS) when applying fungicides before VT can potentially cause a disorder known as arrested ear development. Arrested ear development can greatly reduce ear size and kernel number, leading to a potentially large reduction in yield. In the event of a fungicide application to a field that may be uneven, or had replant areas that are behind in growth stage, spraying fungicides without an NIS will reduce the risk of arrested ear development.

The corn plant is truly amazing! As long as we provide N and careful applications of fungicides and insecticides late in the season, the plant can truly overcome some great odds during the pollination process to develop an ear of corn!

For more agronomic news from Sean Nettleton, Beck's Field Agronomist, please visit his Agronomy Page on

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