Friday, August 28, 2015

Corn, Cotton and the Sugarcane Aphid (High Plains)

Many people on the High Plains are finding what looks like sugarcane aphids on corn and to a lesser extent cotton, and the question we are receiving is whether the aphid will get on these crops and, if so, will it become a problem.

The answer to the first part is a definite YES; they will get on all of our plant species. In the past few weeks we have had billions of winged adults flying from sorghum fields and all of them need to land somewhere. They are basically like flakes of ash from a giant volcanic eruption and will settle out over the landscape.

The answer to the second part of the question is that neither corn or cotton is a good host for the aphid. Small aphid colonies are being found on these crops but they are not expanding rapidly and will not get anywhere near pest status, at least if our aphids behave like sugarcane aphids do in Mexico and south Texas. Sandy Endicott from DuPont Pioneer monitors the sugarcane aphid situation in Mexico and the southern U.S. and provided some perspective to us earlier in the week. In Central Mexico there are four counties where the sorghum crop is a complete loss. The report went on to state that DuPont Pioneer people were finding small colonies on corn, but that there was no concern at this point but they will continue to watch closely. The situation on sorghum in Mexico seems to be extreme yet only small colonies are being found on corn. This matches what our Extension Entomology colleagues Danielle Sekula-Ortiz and Raul Villanueva have reported from the Valley; small colonies only and these do not persist. Corn, being a grass, is much more closely related to sorghum than is cotton, a dicot. The sugarcane aphid has adapted to sorghum and its relatives (including millet) but not to corn, and certainly not to cotton. (Cotton aphids, which look quite similar to sugarcane aphids, are currently being found on southern High Plains cotton.)

Having said all of this, aphids are good at adaptation if they have the genetics to do it. As far as we know, and based on a lot of credible information, none of our crops that are not in the sorghum group are at risk. We would appreciate reports of healthy looking and expanding colonies of sugarcane aphids on any of our non-sorghum crops. Our contact information is here. We don't expect any phone calls but it never hurts to be vigilant.