LSU AgCenter entomologist David Kerns said the aphids have been a sugarcane pest in Louisiana since 1999, but last year became a grain sorghum pest for the first time in the United States. It's unclear what caused the shift, he said, but the insects are nevertheless proving to cause significant damage.
Kerns said, "It seems to have gotten worse. It's not worse as far as the injury they cause, but the infestation is earlier and we're seeing more acres affected. These aphids are found throughout the whole state now."
Last year, the aphids were found in Louisiana, Texas, Oklahoma and Mississippi and along the Gulf in northern Mexico. They have since spread across much of Mississippi and into Arkansas.
Kerns said the 2013 aphid infestation came late in the season and mainly caused harvest efficiency problems. The aphids produce a sticky honeydew that collects on the sorghum and clogs combine harvesters. Sorghum harvest in Louisiana begins in late July and runs through September, depending on geography.
Harvest efficiency will remain a concern, but the aphids' earlier arrival this year could also mean a severe reduction in yields. Aphids feed on carbohydrates, amino acids and moisture, which are critical to plant growth and grain production. In dry conditions, the effects are even worse.
Sugarcane aphids multiply extremely quickly. Small pockets of aphids can expand to a very large population within five to seven days.
Fortunately, Louisiana has been granted an emergency Section 18 registration for the use of Transform, an insecticide that effectively controls sugarcane aphids. Transform provides 90 percent control, which is much better than other insecticides that only have 50 percent to 60 percent control. One application of Transform is usually enough for the entire season.
Several companies and universities, including the AgCenter, are screening sorghum varieties for resistance to sugarcane aphids, Kerns said.
In 2013, Louisiana grain sorghum was valued at $55.1 million and was grown by 276 producers.
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