Aphids are being found in many of the sorghum fields of the Coastal Bend of Texas. Some sorghum fields are no longer protected by the insecticide seed treatments and several kinds of aphids are being found in these fields.
Corn leaf aphids, yellow sugarcane aphids and sugarcane aphids are all being found in sorghum fields. It is important to be able to distinguish between these aphids as their economic thresholds are different.
The Corn Leaf Aphid is usually green, with dark cornicles (tail pipes) and dark legs. Yellow Sugarcane Aphids are yellow and appear hairy with no obvious cornicles. The Sugarcane aphid is yellow to light tan with dark cornicles and tarsi (feet).
Corn leaf rarely reach damaging populations. They would require more than 100-300 per leaf to reduce yield. This aphid is generally thought to be beneficial as it provides a food source for aphid predators prior to the arrival of the other, more damaging, species of aphids.
The yellow sugarcane aphid is more damaging at lower populations because the yellow sugarcane aphid (YSA) injects a toxin into the plant. An insecticide application would be justified when ten to forty percent of plants at the one- to three-leaf stages are infested.
For sugarcane aphids, treatment should be considered when sugarcane aphid populations exceed 50-125 aphids per leaf. While the aphid is present in many of these fields, there is no cause for alarm until their numbers rise above 50 aphids per leaf.
A new Extension publication “Sugarcane Aphid: Management Guidelines for Grain and Forage Sorghums in Texas” is now available. It can now be accessed HERE. This document provides the most up to date information on managing the sugarcane aphid in Texas sorghum.