Successful pollination in corn

They usually shed pollen during mid-morning because of less heat and sunlight. As the anthers dry and split, pollen falls into the open air.

Pollen grains are only viable a few minutes after this release before they deteriorate. Each tassel usually sheds pollen for about five days, and pollination across the field can last up to two weeks.

Each silk that extends from the ear attaches to a single ovule, or potential kernel. A grain of pollen must contact each individual silk in order for that ovule to develop into a kernel.

Silk emergence begins at the base of the ear and extends to the tip of the ear over four to eight days. Silks will continue to elongate up to 10 days until pollination occurs but will become less viable over time as they grow less receptive.

Stress at pollination can reduce yield. High temperatures can destroy pollen particles and reduce the volume of viable pollen or delay silk emergence in the plant.

This causes the plant to miss the window of the majority of pollen being released. Even if pollination is successful, extreme conditions caused by drought will cause the plant to abort kernels. This occurs from the ear tip back until the number of viable kernels is adequate for the growing conditions.

High levels of humidity help reduce evaporation from the plant and keep the silks moist. Most pollen shed starts early in the morning and lasts until around 10 a.m. before the temperatures climb. In July 2012, we recall that in addition to dry soil, most days began in the mid 90s with low humidity, and the thermometer climbed to triple digits during the afternoon for about two straight weeks.

If dry conditions continue, we could find some tip-back kernel abortion on many soil types this year. Up until this point, moisture has been limited but temperatures have been cooler.

The yield potential of this corn crop will be revealed during the next few weeks because moisture will be needed to keep silks viable for successful pollination.

Another issue that can interrupt pollination is Japanese beetle or corn rootworm beetles clipping the silks. This problem rarely requires an insecticide treatment because silks can grow up to 1.5 inches each day.

Possible candidates for spraying are fields that are less than 50% pollinated, have three to five beetles per plant, and have less than 0.5 inch of silks present.

Pollination results can be found two weeks after the tassel completely emerges from the whorl. Gently removing the husk will reveal the cob and silks. Silks that fall away after giving it a shake pollinated successfully. Silks that remain attached failed to pollinate.

For more information, contact the Daviess County Cooperative Extension Service at 270-685-8480.

Potato leafhopperPotato leafhopper (PLH) is a key pest of alfalfa and it’s time to begin watching for it. PLH is a migratory insect that moves north on warm south winds from the Gulf States each spring.

PLH can affect alfalfa in several ways. Insertion of their piercing, sucking mouthparts to feed on sap physically damages vascular tissues of stems and leaves and blocks the phloem. Hopperburn, the characteristic symptom, results from the accumulation of photosynthates in leaves. It begins as a V-shaped wedge of yellow extending from about the middle of the leaf to

the tip.

PLH’s impact on plants is significant and can include stunted growth, premature leaf drop, reduced root carbohydrate reserves, and drastic reductions in protein content of hay. In sufficient numbers, PLH can reduce yields up to 25% and lower crude protein, vitamin A, carotene, calcium, phosphorus, and digestible dry matter content.

A single, well-timed application of any one of several insecticides will provide excellent leafhopper control. A 35-day harvest schedule generally keeps leafhoppers from building to large numbers. Cutting drives the winged adults out of the field. The wingless nymphs are unable to leave and most starve or die from some other cause before regrowth starts.

Clint Hardy is the agricultural extension agent for the Daviess County Extension Office. He can be reached at 270-685-8480.