What is in this article?:
- Will Bt corn pay off for Georgia growers?
- Reduces risk of insect damage
• There are three situations where planting hybrids containing Bt traits provides a clear benefit.
Reduces risk of insect damage
Bt technology reduces the risk of insect damage, thereby allowing for later plantings, although late plantings have lower yield potential and increased risk of damage by diseases.
Studies in 2009-2011 compared the yield of hybrids with single trait YieldGard — corn borer and Genuity VT3 PRO to a similar non-Bt hybrid in trials planted at the recommended and late planting times at Plains and Tifton, Ga.
In trials at the recommended planting time, hybrids with Genuity VT3 PRO averaged 0.96 bushels per acre more than the hybrids with YieldGard-CB and 2.35 bushels per acre more than non-Bt hybrids.
A more consistent response occurred in trials at later planting times where hybrids with Genuity VT3 PRO averaged 4.10 bushels per acre more than hybrids with YieldGard — CB and 9.11 bushels per acre more than non-Bt hybrids.
Situation 2. Northwest Georgia including the Limestone Valley, which consistently has high corn borer populations.
Several species of corn borers occur in Georgia, but corn borers normally do not reach damaging levels throughout most of the state. The exception is northwest Georgia including the Limestone Valley.
In this area, the Southwestern corn borer occurs and it usually is worse in corn after corn in later plantings, but can damage rotated corn planted on time.
While yield response varies with infestation level, trials near Calhoun, Ga., found a 5 to 15 bushel-per-acre response to YGCB Bt corn. More recent studies in northern Alabama found a 9 bushels per acre advantage due to Southwest corn borer control.
Situation 3.Non-rotated (corn after corn) in the northern half of Georgia, where Western corn rootworm can be a problem.
This is a very uncommon situation. There have been only a handful of fields in Georgia with damaging infestations of Western corn rootworm. All were dairy operations in the northern half of the state growing corn in the same fields for several years.
Western corn rootworm larvae attack roots mid-season. It is only a pest of continuous corn and is controlled by rotation.
As little as one year rotated out of corn every three or four years will control this insect in Georgia.
Scout fields during pollination because adults are easily seen feeding on silks and tassels. Bt rootworm traits are very effective.
To get rootworm traits, you will need to plant a stacked product with a rootworm trait. Bt rootworm traits do not control wireworms, white grubs, or Southern corn rootworm in the seedling stage.
(Researchers across the South are trying to get a handle on the relative merits of Bt corn in the area. For a look at the situation in Alabama, click here. There have also been reports of insect resistance developing in Bt corn planted in the Midwest. Southern growers are being urged not to ignore that threat. For the story, visit http://southeastfarmpress.com/grains/don-t-ignore-resistance-threat-rootworms-bt-corn).