Stream baiting in southern Louisiana for Phytophthora ramorum

Abstract

The use of stream monitoring is an important method for early detection of Phytophthora ramorum. Five different waterway locations representing different ecosystems and potential P. ramorum inoculum sources across southern Louisiana were monitored for P. ramorum using bait bags containing whole Rhododendron 'Cunningham's White' leaves from December 2010 to January 2011. After 1 week, the leaves were retrieved and 30 leaf disks (11 mm diameter) per bait bag were taken from necrotic areas of the exposed leaves and placed on a Phytophthora-selective agar medium (PARPH+V8) or 2 percent water agar and incubated in the dark at 20 °C. Plates were monitored for mycelial growth, and suspected Pythium and Phytophthora species were transferred individually to V8 agar to obtain pure cultures. The pure cultures were identified using internal transcribed spacer polymerase chain reaction (ITS PCR). Thirty-four cultures containing 10 different Oomycete species were positively identified from all locations, including: Phytophthora sp. (2.9 percent), P. cryptogea (11.8 percent), P. taxon sylvatica (11.8 percent), Pythium sp. (14.7 percent), Py. aphanidermatum (2.9 percent), Py. diclinum (14.7 percent), Py. litorale (29.4 percent), Py. sterilum (2.9 percent), Py. tumidum (5.9 percent), and Py. undulatum (2.9 percent). The Amite River was the only stream baiting study area to contain species of Phytophthora. Phytophthora ramorum was not found.

Parent Publication

• Proceedings of the sudden oak death fifth science symposium

Citation

Preuette, Jason; Collins, Daniel; Williams, Ashley; Deahl, Kenneth; Jones, Richard. 2013. Stream baiting in southern Louisiana for Phytophthora ramorum. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 159.