Sunday, August 30, 2015

Distribution Map Updated 8.29.15

Dr. Robert Bowling has just updated the sugarcane aphid distribution map. He records a new discovery in Kentucky and a general spread in the west.

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.

Monday, August 24, 2015

Latest Map Shows Spread

Dr. Robert Bowling has updated the sugarcane aphid map to reflect a further expansion of the aphid's range.

Saturday, August 15, 2015

Map Updated to Reflect Spread North and West

Dr. Robert Bowling has issued a new version of the sugarcane aphid distribution map to reflect the aphid's expansion in the second week of August. 

Friday, August 14, 2015

Sugarcane Aphids Moving North to the Texas Panhandle

After last week's confirmation of Sugarcane aphids (SCA) in Ochiltree county, we have more confirmations and reports of the SCA infesting more fields in the Texas Panhandle. There is confirmation that SCAs are in Castro, Carson, Deaf Smith, Gray, Hansford, Oldham, Randall, and Wheeler counties. And there are reports of them being found in Moore county. Fields in Donely, Carson, Deaf Smith, Oldham, and Randall counties were at treatable levels. 

Sugarcane Aphid Threshold Lowered for the Texas High Plains

Now that we have had at few weeks of experience with field-scale sugarcane aphid control in the southern High Plains, it appears that we need to move to a more conservative treatment threshold than the one currently in use. What we are finding in commercial fields and our insecticide trial is that our insecticides do not seem to be working quite as well as they do in more southern locations with higher humidity and less intense sunlight. Whether our environment affects the insects, plants and/or insecticides differently is unknown, and what we are seeing could be a combination of all three factors – or two or one or none, we just don’t know. Insecticide coverage issues may also be in play. We could be experiencing insecticide interception by excessive honeydew such that some of the insecticide never gets to the leaf surface.  We also do not know the importance of reduction in coverage and canopy penetration attributable to aerial application rather than ground application with higher volumes of water. Additionally, we also have reports of narrow row fields (less than 36 inches) having reduced insecticide efficacy, and this of course is a coverage issue.

The preceding paragraph is basically to say that we are not sure what is causing reduced control. We want to make it absolutely clear that there is no reason to think this is a resistance issue. However, with regard to application timing the prudent thing to do is to initiate insecticide applications sooner, before the aphids reach 50-125 aphids per leaf. For that reason we are recommending the action thresholds in use in Mississippi.

The threshold for soft dough stage sorghum is when 30% of the plants are infested and there are localized areas of heavy honeydew and established aphid colonies. This threshold would trigger significantly earlier insecticide applications than our Texas threshold of an average of 50–125 aphids per leaf. The full explanation of the Mississippi threshold can be found here: . Note that this document estimates a 21% yield loss if fields at soft dough stage are left untreated after reaching the threshold. Missing an application at the boot stage threshold of 20% of plants infested with localized heavy honeydew and established aphid colonies would cause a 67% reduction in yield.

Of course another prudent step would be to increase the insecticide rate if possible. Bayer CropScience has some good recommendations for tank additives on the High Plains. Insecticide applications made at relatively low to normal numbers of aphids can be tank mixed with MSO/silicone blends. For heavier infestations they are recommending that Crop Oil Concentrate or High Surfactant Crop Oil be added at the recommended rates. The thought here is do drive the insecticide deeper in to the canopy. 

Wednesday, August 12, 2015

Bayer CropScience Recommending Higher Rate of Sivanto

Russ Perkins, Technical Service Rep., for Bayer CropScience stated yesterday that the company is now recommending Sivanto 200 SL be applied at 5 floz per acre for control of sugarcane aphid infestations. Also, Jodie Stocket, Dow AgroSciences rep., indicates the recommended rate of Transform WG is still 1.0 oz per acre.

Monday, August 10, 2015

New Mexico and Top Tier of Texas Infested

Robert Bowling has updated the sugarcane aphid infestation map to, in part, reflect Jane Pierce's discovery of aphids near Clovis, New Mexico, and a confirmed report from Ochiltree County at the top of the Texas Panhandle. Dr. Pierce is an entomologist with New Mexico State University and her discovery in New Mexico is a first for the State.

The latest map does not yet reflect the reality that many southern High Plains counties are now applying insecticides to aphids at or over the threshold.