@article{roe_young_iwasa_wyss_stumpf_sparks_watson_sheets_thompson_2010, title={Mechanism of resistance to spinosyn in the tobacco budworm, Heliothis virescens}, volume={96}, DOI={10.1016/j.pestbp.2009.08.009}, abstractNote={Topical laboratory selection of tobacco budworm larvae, Heliothis virescens, with technical spinosad for multiple generations resulted in larvae 1068-fold resistant to topical applications of the insecticide and 316.6-fold resistant to insecticide treated diet as compared to the parental strain. The penetration of 2′-O-methyl[14C]spinosyn A across the cuticle of the susceptible (parental) and selected (resistant) tobacco budworms increased with time 3–12 h after application. A trend of reduced penetration in the resistant strain was found but the differences were not statistically significant. 2′-O-methyl[14C]spinosyn A when injected into the hemocoel was not metabolized 96 h after treatment in both the susceptible and resistant strain, suggesting that a change in metabolism was not the mechanism of resistance. Electrophysiological studies indicated that dose-dependent spinosyn A-induced currents occurred in neurons from spinosyn resistant and susceptible (adult) tobacco budworms. At both 10 and 100 nM spinosyn A, however, the amplitude of these currents in the resistant insects was significantly smaller than the amplitude of currents observed from neurons from susceptible tobacco budworm adults. This suggests that neurons from resistant insects have decreased sensitivity to spinosyn A. However, the reduced inward currents in the resistant strain may or may not be related to the mode of action of the spinosyns. No statistically significant cross-resistance was noted for the spinosad resistant tobacco budworms for topical applications of permethrin (Pounce®), profenofos (Curacron®), emamectin benzoate (Denim®), or indoxacarb (Steward®). A statistically significant reduction in susceptibility to acetamiprid (Mospilan®) in artificial diet as determined from a resistance ratio of 0.482 was found.}, number={1}, journal={Pesticide Biochemistry and Physiology}, author={Roe, Richard and Young, H. P. and Iwasa, T. and Wyss, C. F. and Stumpf, C. F. and Sparks, T. C. and Watson, G. B. and Sheets, J. J. and Thompson, G. D.}, year={2010}, pages={8–13} }
 @article{thompson_young_edens_olmstead_leblanc_hodgson_roe_2004, title={Non-target toxicology of a new mosquito larvicide, trypsin modulating oostatic factor}, volume={80}, ISSN={["1095-9939"]}, DOI={10.1016/j.pestbp.2004.06.009}, abstractNote={Trypsin modulating oostatic factor (TMOF), a peptide hormone originally isolated from the ovaries of adult Aedes aegypti, is currently under commercial development as a new pesticide chemistry with a novel mode of action for the control of larval mosquitoes. The objective of the current research is to evaluate potential risks of the use of TMOF as an insecticide on non-target organisms. TMOF (YDPAP6) was degraded in vitro (as determined by HPLC and LC/MS) to DPAP6, PAP6, and then AP6 by leucine aminopeptidase, a pancreatic enzyme found in the digestive system of vertebrates. The rate of degradation of TMOF and PAP6 was significantly greater than that of DPAP6, while no metabolism of AP6 was found. TMOF technical insecticide was produced on a commercial scale by recombinant yeast (heat-killed before application). The technical TMOF when administered in a single dose by gavage to male and female mice at 2000 mg dry weight/kg body weight produced no negative effects as compared to controls up to 12 days after treatment. When male and female mallard ducks were treated by gavage with 1250 mg dry weight of technical TMOF/kg body weight each day for 5 days, again no toxic effects were noted through 35 days after the last treatment. TMOF technical insecticide was also applied to the shaved skin of male and female rabbits at the rate of 2000 mg/kg for 1–2 days, with no effect. The end point observations in these in vivo experiments were mortality; changes in growth rate, behavior, body structure, and color; and possible lesions observed during necropsy. Finally, Daphnia incubated with technical TMOF in rearing water at the level of 1.0 × 106 yeast cells/ml (10 mg/ml) also demonstrated no negative effects on mortality, growth, molting, time to first brood, and production of viable neonates. It appears from these studies that TMOF can be degraded by vertebrate digestive proteases and technical TMOF is not toxic to the non-target organisms examined.}, number={3}, journal={PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY}, author={Thompson, DM and Young, HP and Edens, FW and Olmstead, AW and LeBlanc, GA and Hodgson, E and Roe, RM}, year={2004}, month={Nov}, pages={131–142} }
 @article{wyss_young_shukla_roe_2003, title={Biology and genetics of a laboratory strain of the tobacco budworm, Heliothis virescens (Lepidoptera : Noctuidae), highly resistant to spinosad}, volume={22}, ISSN={["1873-6904"]}, DOI={10.1016/S0261-2194(02)00153-9}, abstractNote={Tobacco budworm larvae, Heliothis virescens (F.), were collected from the field in North Carolina in 1996 and 1997 and established as a laboratory (parental) strain. When a subset of these insects was selected by the topical application of technical spinosad (a mixture of spinosyns A and D) every generation for 13 generations, they became highly resistant to the insecticide. The resistance ratio for topically applied spinosad based on differences in the LD50 between the parental (susceptible) and the resistant (generation 19) strain was 669-fold when fourth stadium larvae were treated. The susceptible strain LD50 18d after treatment was 0.11μg of active ingredient per larva while the LD50 for generation (G) 19 of the resistant strain was 73.55μg per larva. Reciprocal single pair matings between the resistant and the parental strain and backcrosses of F1(R×S) females with resistant males indicated that a non-sex linked, (partially) recessive single gene was responsible for spinosad resistance. The F1 larvae were only slightly (5.3–5.6-fold) resistant compared to the parental strain. The stability of resistance was tested by removing spinosad selection for five generations. In the absence of immigration of susceptible budworms into the population and insecticide treatments, the LD50 decreased only 1.4-fold. The only differences noted in the biology of the parental and resistant strain was that the resistant males developed slower as larvae and emerged as adults later than the susceptible males and had a slightly smaller 1d old pupal wet weight. However, when 80% highly resistant and 20% parental moths of both sexes were allowed to mate freely, the majority of the offspring (84.6%) were susceptible to spinosad. This suggests a reduced reproductive competitiveness for the resistant strain.}, number={2}, journal={CROP PROTECTION}, author={Wyss, CF and Young, HP and Shukla, J and Roe, RM}, year={2003}, month={Mar}, pages={307–314} }
 @article{young_bailey_roe_2003, title={Spinosad selection of a laboratory strain of the tobacco budworm, Heliothis virescens (Lepidoptera : Noctuidae), and characterization of resistance}, volume={22}, ISSN={["1873-6904"]}, DOI={10.1016/S0261-2194(02)00147-3}, abstractNote={The potential for insect resistance to the spinosyns, a novel class of insecticide chemistry, was examined using a laboratory strain of the tobacco budworm, Heliothis virescens (F.), originally collected from tobacco at sites in North Carolina. Technical grade spinosad (spinosyns A and D), was topically applied to third instars. Initially 533 third instars were used but one to two thousand larvae were treated per generation thereafter. Initially mortality ranged from 75% to 85% with doses of 0.044–0.088 μg per larva, until the fifth generation (G5) when mortality decreased. The selection dose was subsequently increased every generation from G5 to G11 in an attempt to restore mortality to >70%. After six generations of selection, the LD50 of the selected budworms was 1.68-times that of the parental generation (G1) as estimated 15 d after treatment. By G14, the topical LD50 of the selected insects was 1068-fold greater than the parental generation. Four additional populations of the budworm from the southeastern US demonstrated similar LD50s to spinosad as our parental strain, suggesting that the parental budworms from North Carolina were representative of field populations elsewhere. The resistance ratio determined with spinosad (formulated as Tracer®) in heliothine diet was 314-fold at 15 d after the start of exposure. Injection of spinosad into the larval hemocoel resulted in a >163-fold resistance ratio 15 d after injection, indicating that resistance could not be explained simply by altered penetration alone. Mortality was delayed in the resistant relative to the parental generation regardless of whether third instars were topically treated or exposed to treated diet. Spinosad resistance was also expressed in G14 adults, indicating that an adult vial test would be feasible for monitoring resistance. A feeding disruption assay was developed to monitor larval resistance in the field.}, number={2}, journal={CROP PROTECTION}, author={Young, HP and Bailey, WD and Roe, RM}, year={2003}, month={Mar}, pages={265–273} }
 @article{young_larabee_gibbs_schal_2000, title={Relationship between tissue-specific hydrocarbon profiles and lipid melting temperatures in the cockroach Blattella germanica}, volume={26}, number={5}, journal={Journal of Chemical Ecology}, author={Young, H. P. and Larabee, J. K. and Gibbs, A. G. and Schal, C.}, year={2000}, month={May}, pages={1245–1263} }
 @article{roe_bailey_zhao_young_carter_gould_sorenson_kennedy_bacheler_1999, title={Assay kit for species and insecticide resistance diagnosis for tobacco budworm and bollworm in cotton}, number={1999}, journal={Beltwide Cotton Conferences. Proceedings}, author={Roe, R. M. and Bailey, W.D. and Zhao, G. and Young, H.P. and Carter, L.M. and Gould, F. and Sorenson, C.E. and Kennedy, G.G. and Bacheler, J.S.}, year={1999}, pages={926–930} }
 @article{young_bachmann_schal_1999, title={Food intake in Blattella germanica (L.) nymphs affects hydrocarbon synthesis and its allocation in adults between epicuticle and reproduction}, volume={41}, ISSN={["0739-4462"]}, DOI={10.1002/(SICI)1520-6327(1999)41:4<214::AID-ARCH5>3.0.CO;2-7}, abstractNote={The causal relationship between food intake and hydrocarbon synthesis was examined in vivo and in vitro. Fed Blattella germanica (L.) nymphs synthesized hydrocarbons in a stage-specific manner, with high rates occurring in the first 6 days of a 13-day last stadium, in relation to feeding. A similar pattern was exhibited in vitro by sternites and tergites from fed nymphs. In contrast, starved nymphs synthesized hydrocarbons at normal rates for the first 2 days, but then synthesis declined and ceased by day 6. Their abdominal sternites and tergites displayed a similar biosynthetic pattern in vitro, showing that starved tissues lost the capacity to synthesize hydrocarbons, even when provided appropriate nutrients. Synthesis resumed within 2 days of being fed on day 6, reaching a maximum rate 6 days later. Some hydrocarbon appeared on the nymphal cuticle, but almost 4-fold more hydrocarbon was internal in hemolymph lipophorin, fat body, and the developing imaginal cuticle. Because most hydrocarbon synthesized in nymphs provisions the adult, and synthesis is related to food intake, we examined trade-offs in allocations in food-limited insects. Nymphs provided with insufficient quantities of food allocated normal amounts of hydrocarbons to the nymphal epicuticle, but molted into smaller adults with significantly less internal hydrocarbons. These cockroaches directed nearly normal amounts of hydrocarbons to their epicuticle, oocytes, and oothecae, at the cost of internal hydrocarbon reserves for repair and subsequent gonotrophic cycles. Hydrocarbons, thus, appear to serve an important cross-stadial resource and the object of competition among several nymphal and adult tissues. Arch. Copyright 1999 Wiley-Liss, Inc.}, number={4}, journal={ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY}, author={Young, HP and Bachmann, JAS and Schal, C}, year={1999}, pages={214–224} }
 @article{bailey_young_roe_1999, title={Laboratory selection of a Tracer-resistant strain of the tobacco budworm and comparisons with field strains from the southeastern US}, volume={2}, number={1999}, journal={Beltwide Cotton Conferences. Proceedings}, author={Bailey, W. D. and Young, H. P. and Roe, R. M.}, year={1999}, pages={1221–1224} }
 @article{young_bachmann_sevala_schal_1999, title={Site of synthesis, tissue distribution, and lipophorin transport of hydrocarbons in Blattella germanica (L.) nymphs}, volume={45}, ISSN={["1879-1611"]}, DOI={10.1016/S0022-1910(98)00128-0}, abstractNote={The site of hydrocarbon (HC) synthesis and the amount of HC in various tissues were investigated in relation to developmental stage in the last larval stadium of the German cockroach, Blattella germanica. Abdominal integument linearly incorporated [1-(14)C]propionate into HC for at least 6h in vitro, whereas other body parts synthesized little or no HC. The third through sixth abdominal sternites and tergites were the principal sites of synthesis. High rates of HC synthesis resulted in a fivefold increase in internal HC during the last stadium. We examined the distribution of HC in the hemolymph, fat body, and the developing imaginal cuticle. Hemolymph HC titer was relatively constant at approximately 8&mgr;g/&mgr;l. However, as hemolymph volume increased from 5 to 11&mgr;l in the first 4days of the last stadium, HC content increased and then remained stable the remainder of the stadium. Lipophorin, immunoprecipitated with adult lipophorin polyclonal antibodies, was the only HC carrier protein in nymphal hemolymph and its HC profile was identical to that of hemolymph and similar to that of the epicuticle. The concentration and total amount of hemolymph lipophorin increased until 3days before adult eclosion and declined immediately after ecdysis. The HC content of non-biosynthetic integument (legs, pronotum) doubled during formation of the imaginal cuticle, as did the HC content of sternites, which synthesize HC. HC content of fat body, however, increased threefold during the same period, suggesting that the fat body serves as a storage site for HC during cuticle formation. We conclude that in the last stadium HC is synthesized by abdominal oenocytes, loaded onto hemolymph lipophorin, and transported to fat body and both nymphal and imaginal cuticle. Hydrocarbons associate with the imaginal integument several days before eclosion.}, number={4}, journal={JOURNAL OF INSECT PHYSIOLOGY}, author={Young, HP and Bachmann, JAS and Sevala, V and Schal, C}, year={1999}, month={Apr}, pages={305–315} }
 @article{sites of synthesis and transport pathways of insect hydrocarbons: cuticle and ovary as target tissues_1998, volume={38}, number={2}, journal={American Zoologist}, year={1998}, month={Apr}, pages={382–393} }
 @article{young_schal_1997, title={Cuticular hydrocarbon synthesis in relation to feeding and developmental stage in nymphs of Blattella germanica (Dictyoptera: Blattellidae)}, volume={90}, ISSN={["0013-8746"]}, DOI={10.1093/aesa/90.5.655}, abstractNote={The patterns of hydrocarbon synthesis and transport to the epicuticle were examined in males and females of the German cockroach, Blattella germanica (L.), during the last nymphal stadium. Methods used to extract hydrocarbon from insects were validated in detail. A double hexane extraction for cuticular hydrocarbons and a triple chloroform-metha-nol extraction of homogenized insects for internal lipids removed essentially all hydrocarbon from the respective compartments, whereas the external extraction did not remove hydrocarbon from the interior of the insect. Synthesis in vivo was measured by the incorporation of [1-14C] propionate into methyl-branched hydrocarbon at 2-d intervals throughout the stadium. In both sexes, hydrocarbons were synthesized at increasing rates during the first 2/3 of the stadium, then synthesis ceased 2 d before the imaginal molt. Hydrocarbon synthesis was related to stage-specific food intake in both male and female nymphs. A declining proportion, but relatively constant quantity, of newly synthesized hydrocarbon was transported to the epicuticle as the nymph progressed through the intermolt period. The majority of the newly synthesized hydrocarbon at all ages was retained internally, however, suggesting that they serve as a source of epicuticular and ovarian hydrocarbon in the adult. Gas-liquid chromatography confirmed the patterns of hydrocarbon synthesis and showed a greater accumulation of hydrocarbons internally than on the nymphal epicuticle. Early in the last stadium, the majority of internal hydrocarbon is in the hemolymph, whereas late in the stadium the fraction of internal hydrocarbon in the hemolymph declines, presumably as newly synthesized hydrocarbon begin to associate with fat body and the developing imaginal cuticle.}, number={5}, journal={ANNALS OF THE ENTOMOLOGICAL SOCIETY OF AMERICA}, author={Young, HP and Schal, C}, year={1997}, month={Sep}, pages={655–663} }