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Sacramento, CA, United States

Pickett C.H.,Biological Control Program | Keaveny D.,Pink Bollworm Program | Rose M.,Montana State University
Biological Control | Year: 2013

Concern over non-target effects of imported parasitoids has resulted in much tighter regulations over their release in the United States. Specificity of candidate agents typically rely on small cage studies inside laboratories, which constrains prediction of their ecological host ranges. Few post-release field studies have examined non-target side effects of imported aphelinids (Hymenoptera), or their regional spread. Eretmocerus is one of the more important groups of aphelinids attacking whiteflies worldwide, and several species were imported into the United States for control of Bemisia tabaci (Hemiptera: Aleyrodidae) during the 1990s. Of five species released in California, only Eretmocerus mundus permanently established in the southern San Joaquin Valley. For 10. years a regional survey was conducted to determine their spread and possible alternate whitefly hosts. Over this period of time, Eret. mundus spread throughout the five counties surveyed and continued to be the only candidate that persisted, permanently establishing populations in this largely cotton growing region of central California. Eventually Eret. mundus displaced native Eretmocerus attacking B. tabaci on cotton, and now make up over 95% of the Eretmocerus attacking this pest. Except on one occasion, all Eret. mundus emerging from isolated whitefly nymphs came from B. tabaci (n= 243). Parasitism levels have varied from 7 to 35%, up from less than 1.4% when first measured. The percentage of cotton leaves infested by B. tabaci populations in the San Joaquin Valley has dropped from an average of 28-12.2% during the last three years measured. Most likely this change in infestation level is due to a combination of factors, including the introduction of more selective insecticides, drop in regional cotton acreage, and the permanent establishment of a more specific parasitoid. © 2013 Elsevier Inc.

Bon M.-C.,U.S. Department of Agriculture | Hoelmer K.A.,U.S. Department of Agriculture | Pickett C.H.,Biological Control Program | Kirk A.A.,U.S. Department of Agriculture | And 3 more authors.
Annals of the Entomological Society of America | Year: 2016

Olive fruit fly, Bactrocera oleae Rossi, is a worldwide pest of olives. To discover new parasitoids for a biological control program in California, olives were collected from various locations in the Himalayan foothills (China, Nepal, India, Pakistan) as part of a comprehensive search for B. oleae throughout its range. Wild olives, Olea europaea ssp. cuspidata, were sparsely distributed and B. oleae-infested olives were scarce. Wild olives were most widespread in Pakistan where fly infestation reached 30%. Infested olives in southwestern China were rare, reaching only 5%. Flies were identified morphologically as B. oleae, the first record from China. No B. oleae were recovered from India or Nepal. Mitochondrial gene sequences from NADH dehydrogenase (ND1), cytochrome oxidase subunit 1 (COX1), and 16S rRNA were obtained from flies and compared with B. oleae sequences in GenBank. A single mitochondrial haplotype was found in Chinese flies. Chinese B. oleae represent a maternal lineage based on ND1 and COX1 that is highly divergent from other B. oleae. Phylogenetic analysis by maximum likelihood and Bayesian inference based on the concatenated dataset of B. oleae sequences with sequences of two close subcongeners, Bactrocera biguttula (Bezzi) and Bactrocera munroi White, and analysis of delineation of species boundaries using the genealogical sorting index, supported the idea that Chinese flies share recent common ancestry with B. oleae. Flies were parasitized by braconid wasps, Psyttalia ponerophaga (Silvestri) in Pakistan, and a Diachasmimorpha species in China. Our survey reinforces the possibility of finding new biocontrol agents of olive fruit fly in the Himalayan region. © 2015 Published by Oxford University Press on behalf of Entomological Society of America.

Pena J.E.,University of Florida | Duncan R.E.,University of Florida | Roltsch W.J.,Biological Control Program | Carrillo D.,University of Florida
Florida Entomologist | Year: 2012

The avocado lace bug (ALB), Pseudacysta perseae (Heidemann) (Heteroptera:Tingidae), is a pest of avocado, Persea americana, in Florida, the Caribbean Basin, California and northern South America. Different biotic mortality factors, i.e., the egg parasitoids Erythmelus (Erythmelus) klopomor, a new species of Trichogrammatidae, and the predators, Chrysoperla rufilabris, Paracarniella cubana, Stethoconus vitripennis, and Tingidoletes praelonga, have been reported as natural enemies of P. perseae in Florida. We determined the effect of these biotic factors during 3 seasons, by exposing P. perseae cohorts to known biotic factors, and compared their survival to cohorts protected from these factors. The total percent mortality caused by biotic factors was 16 to 90% above the mortality caused by abiotic factors during 3 seasons.

Buergi L.P.,University of California at Berkeley | Roltsch W.J.,Biological Control Program | Mills N.J.,University of California at Berkeley
Environmental Entomology | Year: 2011

The light brown apple moth, Epiphyas postvittana (Walker), is native to Australia and first was detected in California in 2006. In this study, we regularly sampled populations on Leptospermum laevigatum (Gaertn.) F.Muell. at two sites in San Francisco and on Arctostaphylos densiflora M.S. Baker at two sites in Santa Cruz over a 2-yr period to monitor the abundance, age structure, and voltinism of this potential pest in relation to degree-days. Our results showed that larval abundance declined at two sites, cycled with peaks in midsummer at one site, and remained steady at one site. Generations overlapped at all four sites with the full range of larval instars being present for most of the year, although populations during the winter were predominantly mid to late instars. Accumulated degree-days predict an average of 3.27 and 4.58 generations per year in San Francisco and Santa Cruz, respectively, which matched our observed peaks of late-instar larvae in the field remarkably well. This new information on light brown apple moth phenology in coastal California will be invaluable for the development of effective monitoring and management strategies for this new invader in the studied region. © 2011 Entomological Society of America.

Burgi L.P.,University of California at Berkeley | Burgi L.P.,Oregon State University | Roltsch W.J.,Biological Control Program | Mills N.J.,University of California at Berkeley
Population Ecology | Year: 2015

Resident natural enemies can impact invasive species by causing Allee effects, leading to a reduction in establishment success of small founder populations, or by regulating or merely suppressing the abundance of established populations. Epiphyas postvittana, the Light Brown Apple Moth, an invasive leafroller in California, has been found to be attacked by a large assemblage of resident parasitoids that cause relatively high rates of parasitism. Over a 4-year period, we measured the abundance and per capita growth rates of four E. postvittana populations in California and determined parasitism rates. We found that at two of the sites, parasitism caused a component Allee effect, a reduction in individual survivorship at lower E. postvittana population densities, although it did not translate into a demographic Allee effect, an impact on per capita population growth rates at low densities. Instead, E. postvittana populations at all four sites exhibited strong compensatory density feedback throughout the entire range of densities observed at each site. As we found no evidence for a negative relationship between per capita population growth rates and parasitism rates, we concluded that resident parasitoids were unable to regulate E. postvittana populations in California. Despite a lack of evidence for regulation or a demographic Allee effect, the impact of resident parasitoids on E. postvittana populations is substantial and demonstrates significant biotic resistance against this new invader. © 2014, The Society of Population Ecology and Springer Japan.

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