Wednesday, August 5, 2015

Multiple Aphid Species in Sorghum, What a Year

Some area sorghum fields are experiencing significant numbers of aphids, but not just sugarcane aphid the recently arrived pest from the south. We also have high numbers of yellow sugarcane aphid, greenbug and corn leaf aphid. Of these, the corn leaf aphid is the only one that is not a threat.

Blayne Reed, Ed Bynum and I put out the first sugarcane aphid control experiment today just east of Hale Center. The pre-treatment count averages were something like 70 sugarcane aphids per leaf, 60 yellow sugarcane aphids and 30 greenbugs. (I have not formally tallied the numbers yet, but these are best guesses from my tired brain.)

Dr. Bynum wrote an excellent article on the practical and important differences between sugarcane aphid and yellow sugarcane aphid, and it can be found here. He discusses biology, damage and thresholds.

As you scout fields be sure to note the number of sugarcane aphids, yellow sugarcane aphids and greenbugs separately. As Dr. Bynum notes in his article, we don't have any thresholds for yellow sugarcane aphids on older sorghum so we recommend spraying them on the greenbug damage thresholds. However, if there are a significant number of sugarcane aphids in the field then it would be a good idea to treat the field with an insecticide that took out sugarcane aphids. These insecticides, Transform and Sivanto, are also effective on yellow sugarcane aphid and greenbug. However, the reverse is not true; our traditional insecticides for yellow sugarcane aphid and greenbug are not very effective on sugarcane aphid. So spray to kill all three species - don't leave sugarcane aphid in the field.