Monday, March 21, 2016

Survey for Sugarcane Aphids on Johnsongrass, Hill County, TX

Johnsongrass was surveyed for sugarcane aphid SCA in Hill County on March 17, 2016 by Xandra Morris, Zach Davis and Allen Knutson, Texas A&M AgriLife Extension. Johnsongrass shoots were about 12 inches tall at this time.  Sugarcane aphids were present on 24%, 56% and 62 % of the JG shoots examined at three sites.  The average number of SCA per shoot ranged from 3-24, although a few leaves had several hundred SCA per leaf.   A total of 2,400 SCA were observed on 150 Johnsongrass shoots during this survey. No winged SCA and no parasite mummies were present in these samples. Red imported fire ants were tending SCA colonies. A few bird cherry oat aphids were also present. 

Thursday, March 17, 2016

Kansas aphid find does not mean early spread

News went out today that sugarcane aphids have been found in Kansas, but there is more to the story and the details may be important. The report is here. (Revised on 3/18 to address the greenhouse issue - see italics.) The report says that the aphids were found in a greenhouse, not in the field, and it goes on to discuss the early finds of aphids along the Gulf Coast and suggests the Kansas aphids flew in from the south.

Actually, we don't have many winged aphids in Texas yet; the colonies are still primarily composed of wingless aphids, and winged adults will not be found in great numbers for a while longer. It is possible that the aphids remained in the Kansas greenhouse or nearby greenhouse all winter, and a greenhouse discovery does not mean that the aphids arrived from the south this year (or overwintered locally in the wild and infested the greenhouse this spring). 

Texas A&M AgriLife Extension Entomology has nine overwintering study sites on the High Plains, and Dr. Ed Bynum, Extension Entomologist in Amarillo, examined his overwintering cages in Bushland today. His cages are the most northerly of the nine sites and he reported finding no aphids on Johnsongrass that was just beginning to sprout.  Pat Porter, Extension Entomologist in Lubbock, dug Johnsongrass yesterday and found no aphids on rhizomes or green buds. The remaining eight overwintering study sites will be examined in the next couple of weeks.

Reports from Texas have the aphid as far north as Hill and Comanche counties. Dr. Charles Allen, Associate Department Head, Department of Entomology, reported seeing sugarcane aphids on Johnsongrass near San Angelo last week. However, intense rainfall forced him to abandon the site and he did not collect any aphids. However, since we all have had plenty of practice and know sugarcane aphids when we see them, Tom Green County can be listed on the map of positive counties. 

The bottom line is that the aphids are farther north in Texas this year than we have seen in the past in March, but this does not mean that winged aphids have already spread from the Gulf Coast across the plains to Kansas. 

Wednesday, March 9, 2016

Comanche County Positive for Sugarcane Aphid - March 9th

Blayne Reed, Extension Agent IPM in Hale, Swisher and Floyd counties, reported finding sugarcane aphid in Comanche County on Johnsongrass on March 9th. The plants were just greening up for the season and had two leaves. The small colony was comprised of nymphs, and no adults were observed. Blayne was driving south, and the find was along the highway and not part of a more extensive survey.