Sweet corn sweet corn sweet corn..Southwestern Corn Borer (Diatraea grandiosella)

The southwestern corn borer is another ear feeding and stalk boring insect pest of sweet corn in the western half

of Kentucky. The larval stage tunnels into corn stalks and ear shanks, and will feed on kernels in the ear. Like the European corn borer, southwestern corn borer has two generations each year. Mature larvae spend the winter

below ground in the rotting crowns of the harvested corn. In early May of the following year, the larvae Trans form to the pupal stage. The resulting adults, or moths, emerge from the pupal cases, mate and begin to lay

eggs in mid June. Each female is capable of laying an average of two egg masses a night for about 10 nights. These eggs begin to hatch in 5 to 6 days. The presence of three red stripes on each egg means that it will hatch very soon. Newly hatched larvae, about 1/8-inch long, will move from the leaf into the whorl of the plant to feed for several days. When the larvae become about 3/4-inch long, they will enter the stalk to complete their

development. The mature larvae usually pupate within the tunnel. Moths will emerge from these pupae in 2 to 3 weeks and lay their eggs to start the second generation. Late planted corn is most susceptible to damage from this generation of borers.

Controls

Biological: The predators and parasites of southwestern corn borer are not well understood.

Bt sweet corn hybrids (Attribute™) provide effective full season control of European and southwestern corn borer.

Cultural: Many larvae can be killed if the stalks and field debris are plowed under. However, most of the moths are emerging from field corn of which most is in no-till for soil conservation reasons. Planting date is very important in determining the potential for southwestern corn borer infestation. Extremely early or late planting will increase the potential for borer damage. The first generation can be very damaging to early plantings, while late planted fields are prone to attack by the second. The second generation is usually more damaging to sweet corn than the first.

Monitoring: In whorl stage corn, treat if more than 15% of the whorls are infested with live larvae. It is very important to monitor late whorl stage sweet corn for southwestern and European corn borer, because as the tassel begins to emerge, corn borer larvae will move to other locations on the plant, the ear being potentially one of those. Corn borer control is frequently necessary when tassels begin to emerge from the whorl.

During silking, pheromone traps are used to determine the need and frequency of insecticide sprays to protect the ear. Separate pheromone traps are needed for corn earworm, fall armyworm, southwestern corn borer, and European corn borer during this silking period. The Southwestern corn borer pheromone trap is very effective with some weekly counts exceeding 1000 moths per trap in some areas.

Bt sweet corn is highly effective in controlling European and southwestern corn borer in Kentucky. To a limited extent, some sweet corn producers have tested Bt sweet corn for local fresh market sales, but use of Bt sweet

corn hybrids for European corn borer control comprise less than 1% of the sweet corn market.

Application Alternatives used :

Ambush 2 E (permethrin)- Apply as a foliar application at 6.4 to 12.8 fl oz per acre to a limit of 76.8 fl oz per acre per season.

Asana XL (esfanvalerate)- Apply as a f liar application at 5.8 to 9.6 fl oz per acre to a limit of 96 fl oz per acre per season.

Baythroid 2 (cyfluthrin)- Apply as a foliar application at 1.6 to 2.8 fl oz per acre to a limit of 10 applications per season.

Capture 2E (bifenthrin) - Apply as a foliar treatment at 2.1 to 6.4 fl oz per acre to a limit of 12.8 fl oz per acre per season. The long Restricted Entry Interval limits the use of this product to machine harvested field for

processing. Only a small fraction of the acreage in Kentucky is harvested by machine.

Bt-products (various labels)- Apply as a foliar treatment and reapply as necessary.

Lannate 90 SP (methomyl)- Apply as a foliar treatment at 1/4 to ½ lb per acre to a limit of 8 lb per acre per season.

Pounce 3.2 EC (permethrin)- Apply as a foliar treatment at 4 to 8 fl oz per acre to a limit of 48 oz per acre per season.

Sevin 80 WSP (carbaryl)- Apply as a foliar treatment at 1-7/8 to 2-½ lb per acre to a limit of applications per acre per season. Allow at least 7 days between sprays.

Warrior 1 EC (lambda-cyhalothrin)- Apply as a foliar treatment at 2.56 to 3.84 fl oz per acre to a limit of 3.84 pt per acre per season.