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Title: Forensic pollen geolocation techniques used to identify the origin of boll weevil reinfestation

item Jones, Gretchen

Submitted to: Grana
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2011
Publication Date: 6/20/2012
Citation: Jones, G.D. 2012. Forensic pollen geolocation techniques used to identify the origin of boll weevil reinfestation. Grana. DOI:10.1080/00173134.2012.667832.

Interpretive Summary: Shortly after Tropical Storm Erin passed through Texas in August 2007, more than 150 boll weevils were unexpectedly captured in the Boll Weevil Eradication Program’s Southern Rolling Plains eradication zone. This area had been essentially weevil-free since 2003. It was important to identify the origin of the reinvading weevils, but this required the development of new techniques. In this work, a pollen “fingerprint” or “pollen-print” was developed from pollen recovered from these weevils. The pollen-print of the weevils captured in the Southern Rolling Plains shared pollen of 16 different plant types with weevils captured in the South Texas/Winter Garden eradication zone. When pollen from the reinvading weevils was compared to pollen from weevils captured in the Southern Blacklands zone, there were only 6 pollen types shared. The results of this work gave very clear evidence that the weevils that invaded the Southern Rolling Plains during Tropical Storm Erin almost certainly came from the South Texas/Winter Garden area many miles to the southwest. This work has shown clearly that analysis of pollen types on insects can be a very valuable tool in establishing sources of invading insects, and also in monitoring short-term insect movements over significant distances.

Technical Abstract: The boll weevil, Anthonomus grandis, entered the United States of America in the early 20th century and became a major pest in cotton, Gossypium spp. Shortly after the passage of Tropical Storm Erin on 16 August 2007 through the South Texas/Winter Garden boll weevil eradication zone, over 150 boll weevils were captured in the Southern Rolling Plains (SRP) eradication zone that was essentially weevil-free since 2003. Pollen analyses were made of the SRP weevils and weevils collected in two suspected source zones, Cameron (Southern Blacklands eradication zone) and Uvalde (Winter Garden eradication zone). An additional examination of the palynological evidence and examination of additional pollen residue shed new lights on this event and strengthens the conclusion that the Uvalde area was the source of the SRP weevils. A total of 192 pollen grains from 39 taxa were found in the SRP samples, 1904 pollen grains from 10 taxa in the Cameron samples, and 148 grains from 28 taxa in the Uvalde samples. The SRP weevils shared 16 taxa, including Phermeranthus sp. (flameflower) with the Uvalde BW and only 5 taxa with the Cameron BW. The taxa in common between SRP and Uvalde weevils and the lack in the SRP samples of the dominant Asteraceae “low spine” pollen that occurred in all Cameron samples confirm that the SRP weevils likely originated from the South Texas/Winter Garden eradication zone. Problems associated with this type of entomopalynological research are similar to those in forensic palynology. These problems include the unknown origin of the weevils, pollen contamination, and care and storage of the samples.