Monday, April 4, 2016

Overwintering in Dawson County, Texas, but not Hockley County

Tommy Doederlein, Extension Agent - IPM in Dawson and Lynn counties, checked both of his sugarcane aphid overwintering cages today and found healthy aphid colonies in one of them. There were no aphids on Johnsongrass outside the cage. This cage was located between Lamesa and O'Donnell and was in a more protected location than the cage where no overwintering aphids were found. No winged aphids were found. This is the second consecutive year that Tommy has found aphids in his overwintering cages, but last year's results could not be determined to be conclusive. This year's results are conclusive, and to date Dawson county is the most northerly location in Texas where sugarcane aphid has been documented to overwinter.

Kerry Siders, Extension Agent - IPM in Hockley, Cochran and Lamb counties, examined his Hockley County overwintering cage on March 21st and did not find any sugarcane aphids, but did find yellow sugarcane aphids. He kept some unhatched spherical objects that might possibly be eggs, but nothing emerged from them. Cages to the north in Hale and Swisher counties have yet to be examined because the Johnsongrass is just emerging.

Habitat surrounding the Dawson County cage with successful overwintering.

Last fall an infested sorghum leaf was placed in the cage, and this year's aphids were on the Johnsongrass beneath and near the sorghum leaf; they had not spread to Johnsongrass on the other side of the cage. 

Aphids on Johnsongrass inside the overwintering cage.

Temperature recording probes were placed both inside and outside the cages at the ground surface and at two inches beneath the soil. 

Temperature Data Inside Cage, Top of Soil

Low temperature 20.8 degrees, Feb. 4, 2016
Hours below freezing (across all dates) = 318
Hours below 26 degrees = 46
Hours below 25 degrees = 23
Hours below 24 degrees = 15
Hours below 23 degrees = 11
Hours below 22 degrees = 2

Temperature Data Inside Cage, Buried in Soil at 2 Inches Depth

Low Temperature 36.6 degrees
Hours below freezing = 0