September 6, 2000 | By: Laura Skillman
PRINCETON, Ky.

Corn lodging is becoming a problem in many fields in western Kentucky.

Because the problem results in the stalks falling over, making harvest more difficult, farmers are encouraged to check their fields and consider harvesting any fields that show signs of lodging first, said Paul Vincelli, University of Kentucky plant pathologist.

An earlier harvest may mean corn will have to be dried adding to the cost of production, but lodging can result in a difficult harvest with some of the corn left behind in the field.

The lodging seems to be the result of a combination of factors including weather conditions, disease and insect pests.

Some fields checked in the Green River area of the state last week, showed a general pattern of stalk weakening. The majority of all fields checked were weakened by factors other than insect damage, said Vincelli and Doug Johnson, UK Extension entomologist.

There was evidence of stalk rot diseases but that evidence did not appear to be very consistent in the field inspections, Vincelli said. It is unclear at this time whether the majority of the stalks were weakened from physiological stalk weakening or from infectious stalk rots.

However, much like a human with a weakened immune system is more susceptible to infections, physiological stalk weakening can often predispose plants to infectious stalk rots.

Weather conditions reported this season in some parts of the state set the stage for stalk weakening, Vincelli said. Conditions favorable for high yields create a large ear that requires a large amount of photosynthate. Overly cloudy weather during grain fill provides for reduced photosynthesis, so a high-yielding corn plant will draw reserves from the stalk, leading to stalk weakening.

Factors that might further exacerbate the situation include excessive plant population; excessive nitrogen compared to potash; high nitrogen levels early in the season followed by nitrogen loss through leaching or denitrification; inadequate potash levels; and low stalk strength ratings of hybrids planted.

Johnson said the fields checked did contain substantial populations of both Southwestern and European corn borers but a check of the stalk in the broken area showed the pests were only responsible for 10 to 15 percent of the downed stalks.

Farmers looking at these fields will see the insect damage and may conclude the insects are the cause of the problem and look to Bt corn as a quick fix for next year's crop. That may be especially true if they have Bt gene varieties this year that are showing no lodging problems.

But, Johnson advises caution because the cost of Bt corn seed is higher and there's the question of marketability.

The Bt gene, which controls corn borer, is put in some of the better corn varieties that may have better stand ability so this year's results could be coincidental.

Farmers need to be discerning about how they solve the problem, Johnson said. Bt corn has its place, but in the cases checked by the two UK specialists, the Bt gene would have had little impact.

Vincelli and Johnson recommend that farmers check their fields for signs of lodging. To do that, walk through the field holding your arm at chest level and push the plants 8 to 10 inches, to see if they bounce back or not. Johnson said if it has damage, you can hear it -- the stalk snaps just like when you break a straw.

If 10 to 15 percent of the plants show signs of possible lodging below the ear, farmers may want to consider harvesting those fields first to reduce the potential of downed corn.

Farmers with questions about downed corn or early harvesting can contact their county Extension agent for agriculture and natural resources.

Contact: 

Paul Vincelli, (859) 257-5675; Doug Johnson, (270) 365-7541