Sugarcane beetles being found in Virginia corn crop

Sugarcane beetles have been around a century or so, but rarely have been a pest of row crops in Virginia.

This year several crop-damaging populations have shown up in Virginia corn fields and the results have been devastating on a very small scale.

The 2011 corn crop will be one of the most valuable on record. Protecting the crop against insects, diseases and other yield-robbing factors will be more critical than ever before and the introduction of new insects into the cropping season is just what farmers don’t need.

The sugarcane beetle, as the name implies, is a frequent pest of sugarcane in south Florida and Louisiana and has been problem in corn in most southern states, but rarely in Virginia.

Damage in North Carolina has occurred statewide in some years, but most economically damaging populations are more commonly found in the Piedmont counties.

With one of the largest cotton crops in recent years predicted in the Carolinas and Virginia this year, growers need to be aware that sugarcane beetles also infest cotton.

But by far the biggest threat will come to corn, and even so, the problem is likely to be sporadic and likely will take care of itself by mid-to late June.

However, when you’ve got sugarcane beetles in your corn, there’s little you can do in terms of a curative treatment. Most of the feeding is done 1-2 inches below the soil and once young corn stalks begin to fall over, typically it’s too late to use an insecticide.

These tiny insects are mostly nocturnal feeders and can be both difficult to find and to kill. Typically, even if a grower decides to use one of a number of insecticides that will kill these insects, getting the material to the adult beetle is tough.

Granular organophosphate insecticides such as Lorsban 15G and Counter 15G applied in the seed furrow or banded across the row can reduce sugarcane beetle infestations in field corn.

Seedling injury reduced

Seedling injury has also been reduced in field plots treated with a variety of different insecticides as rescue treatments including Capture 2EC, Lorsban 4EC and Baythroid 2EC. In spite of these treatments, however, significant plant injury and ultimate yield losses still occur.  

In corn fields with large infestations of the insect, growers can expect severe damage to the corn root system. Young plants are the most susceptible and already several fields with damaging populations of sugarcane beetle in corn have been reported.

As it feeds, the sugarcane beetle adult chews a large gouge in the stem at the base of the plant. Eventually the damage to corn shows up as dead plants, plants with a dead heart, or stunted plants.

Damaged plants may have a light streak along the margin of the leaf. Surviving plants may develop multiple, unproductive stems.

By the time damage appears, it is often too late to replant the corn. Sugarcane beetle adults will also feed on turf and pasture grasses, causing considerable damage in some cases.

Damage occurs from late April to late May in North Carolina and Virginia.

Jimmy Ward, a local manager for Crop Production Services in Hopewell, Va., has seen a couple of corn fields hit by sugarcane beetle and on a small scale the results haven’t been pretty.

Former Isle of Wight Extension Agent and current Pioneer Agronomist Glenn Rountree says his experience with sugarcane beetle hasn’t been very encouraging either.

“I looked at an 8-9 acre field of corn (in mid-May), and the damage was bad. By bad, it was severe enough for the farmer to look at filing for crop insurance,” Rountree says.

Ward, who found the first Virginia field infested with sugarcane beetles this season says, “We found the first insects in a 10 acre field next to a hay field. The corn field had had a grass cover crop. Subsequently other fields in which sugarcane beetles were reported also were fields that had a cover crop and/or were near grass fields,” he says.

“In this particular field, smaller corn had the growing point bit out of it and was putting up multiple tillers. The larger corn was leaning over and the damage looked a lot like we typically see in zinc deficient soil.

“When we dug down at the base of the corn, about a half inch below the surface, we could easily find the small black beetles. It’s about the size of a Japanese beetle and feeding was evident on the base of the corn plant.

“In talking with people in other states who have dealt with this pest for several years, we found the beetles tend to be in areas with sod cover or with grasses. This is the type scenario in which this insect has been found so far this year in several Virginia fields,” Ward says.

“It’s going to be hard for growers to deal with these pests. Spraying in the daytime isn’t going to work, because sugarcane beetles feed mostly at night and go back underground in the daytime. It seems that daytime temperatures in the 80 degree range are a trigger for nighttime feeding,” Ward adds.

“Growers need to be aware of sugarcane beetles, but so far it has occurred very sporadically in Virginia.

Hot spots

Even fields that are infested have hot spots in which corn plants are destroyed, but it’s questionable whether there is any reason to go out and spray corn to prevent infestations from occurring, unless you are growing it in areas adjacent to a sod field or behind a grass cover crop” he says.

The big fear is that the problem will continue to be more widespread in the future and become a serious economic pest to corn production in Virginia and surrounding states.

If corn growers decide to spray for sugarcane beetles, Ward suggests spraying early in the morning, the closer to dawn the better.

A number of seed treatments have shown to help prevent feeding by adult sugarcane beetles and a number of systemic organophosphate and neonictinoid-containing insecticides have proven effective in killing the beetles.

The key to managing the pest is early recognition. If there is damage, it’s a good bet there are more insects in the field, especially if the field had a ryegrass cover crop. Replanting damaged hot spots and treating the entire field may be an option in severe infestations of the insect, Ward says.

He stresses that applying an insecticide on corn that is already damaged is not going to do much good.

Though sugarcane beetles are a frequent pest in North Carolina, veteran North Carolina State Corn Specialist Ron Heiniger says there have been no reports of the insect in corn this year.

“When we heard about sugarcane beetles occurring in southeast Virginia, we sent out a notice to all our county Extension personnel asking if they had any reports of damage to corn that matches damage from these beetles, and we didn’t get any indication anyone has seen the problem so far this year,” Heiniger says.

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