Introduction of the cereal leaf beetle parasitoid Tetrastichus julis (Hymenoptera: Eulophidae) into California

Abstract

ABSTRACT In 2013, cereal leaf beetle was reported for the first time in California. Most likely it moved south from Oregon into the state’s northern region. In response, the gregarious larval endoparasitoid Tetrastichus julis (Hymenoptera: Eulophidae) was collected and transferred to a field insectary at the University of California Intermountain Research and Extension Center in Tulelake. From 2014 to 2018 the insectary was maintained to propagate T. julis for redistribution to commercial grain fields in northern California experiencing infestations by this pest. Sequential plantings of oats, preceded by winter wheat at this insectary provided a constant source of pre-head, lush oats throughout the summer. In turn, a reliable source of cereal leaf beetle hosts was produced for T. julis, which also increased in numbers. These parasitoids were released into infested commercial fields of wheat in the Klamath Basin region of northern California. Over four years beginning in 2016, annual surveys of the region showed that cereal leaf beetle populations declined while T. julis rapidly increased. Our releases, in addition to the natural spread of this parasitoid south from Oregon played a key role in the beetle population declining by nearly 90% over this period.