- Author: Therese Kapaun
The emergence cycle of captured walnut twig beetles (WTB) is being documented at LREC. The tiny beetles, in addition to a suite of other log-dwelling insects (including their parasitoids), emerge nearly year-round from infested walnut logs that are housed in outdoor enclosures. The insects are collected weekly, and then sorted, sexed, and counted. In 2013, WTB emerged from March-September, with peak emergence in mid-late June. In 2014, peak WTB emergence peak occurred in May-June, and emergence counts are falling off rapidly now that it is midsummer. One notable week's collection was May 13-20, with 1940 emerged WTB from one of the six emergence chambers.
Dr. Elizabeth Fichtner (Farm Advisor, Tulare UCCE) has recently acquired Yelena Martinez, a participant in the College of Sequoias SURGE (Student Undergraduate Research Group Experience) program, to assist Katie Wilson (UCCE Tulare) and Therese Kapaun (LREC) with the staggering number of weekly counts during the peak season. This photo shows Yelena viewing insects under a dissecting microscope and separating the different species into containers. Katie and Therese will continue to monitor and count emergences for at least the next twelve months.
WTB has been recently found to be associated with Thousand Cankers Disease, a fungal pathogen of several walnut species in North America. The pathogen was also recently reported on black walnut in Italy. More information on the disease, as well as the beetle can be found at:
UCCE In a Nutshell Newsletter Tulare County (pages 5-7)