Showing papers in "Journal of Economic Entomology in 1996"
TL;DR: Support is provided for the hypothesis that a management strategy of providing flower borders for fields can result in more efficient biological control of aphids by syrphid larvae, thus reducing the reliance on insecticidal control.
Abstract: Hoverflies (Diopters: Syrphidae) are potentially important in arable and horticultural crops as biological control agents. Many species lay their eggs near aphid colonies, and their larvae are aphidophagous. Adult overflies need nectar for energy and the protein from pollen for sexual maturation and egg development. Phacelia tanacetifolia Bentham (Hydrophyllaceae), a North American annual species that is a good source of pollen for syrphids, was drilled in the margins of 3 winter-wheat fields on a farm in North Hampshire, southern United Kingdom in 1992 and in different fields in 1993. Numbers of hoverflies in yellow water traps, oviposition rates, and aphid densities in these fields were compared with those in control fields. In 1992 in the fields bordered with P. tanacetifolia , significantly more hoverflies were captured in the traps but differences in oviposition or aphid numbers were not significantly different between treatments. This may have been because the wheat matured early so that it was less suitable for syrphid oviposition when gravid females were in the field. In 1993, differences between numbers of adults caught in experimental and control fields were not significantly different. However, significantly more eggs were found in fields with P. tanacetifolia than in control fields and significantly fewer aphids were present in these fields than in controls during the 4th wk of the experiment when many 3rd-instar syrphid larvae were present in the crop. Our results provide support for the hypothesis that a management strategy of providing flower borders for fields can result in more efficient biological control of aphids by syrphid larvae, thus reducing the reliance on insecticidal control.
231 citations
TL;DR: A large scale and long-term study on seasonal population fluctuationsof Anastrepha fruit flies in commercial mango orchards in the Soconusco Region, Chiapas, Mexico finds significant differences in terms of total numbers of flies captured per orchard and Anastsrepha species diversity in each orchard.
Abstract: We report the results of a large scale (5 orchards) and long-term (5 yr) study on seasonal population fluctuationsof Anastrepha fruit flies in commercial mango orchards in the Soconusco Region, Chiapas, Mexico. Out of 10 Anastrepha species present in these orchards, West Indian fruit fly, A. obliqua (Macquart), and Mexican fruit fly, A ludens (Loew), accounted for 96.6% of all individuals captured in McPhail traps. A obliqua was by far the dominant species, accounting for 66.1% of all individuals captured. Anastrepha populations fluctuated markedly from year to year during our study. Furthermore, even though we worked in orchards that were relatively close to each other, we discovered significant differences in terms of total numbers of flies captured per orchard and Anastrepha species diversity in each orchard. Most flies (62.3%) were captured in traps placed in the periphery of orchards (i.e., edge traps). Also, most (≈90%) of the mangoes sampled in commercial orchards were infested by A. obliqua , despite the fact that significant numbers of A ludens adults were present in every orchard. In contrast, mangoes sampled at higher elevations were predominantly infested by A. ludens . We compare our results with similar studies in other parts of Mexico and Latin America and discuss our findings in light of their practical implications.
154 citations
TL;DR: Adult tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), collected in July and August from 4 cotton fields in the Mississippi Delta with plant bug control problems were tested with a glass vial bioassay for resistance to insecticides.
Abstract: Adult tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), collected in July and August from 4 cotton fields in the Mississippi Delta with plant bug control problems were tested with a glass vial bioassay for resistance to insecticides. Resistance levels determined for the different field populations were compared with those found by using the glass vial bioassay and susceptible plant bugs collected from weeds near Crossett, AR. Significantly higher levels of pyrethroid resistance were found in plant bugs from all 4 cotton fields as compared with pyrethroid resistance in bugs from Crossett. Plant bugs from one cotton field near Schlater, MS, were reared through 9 generations in the laboratory and tested in various generations for resistance to 4 pyrethroid, 5 organophosphorus, and 1 cyclodiene insecticide. Plant bugs in this resistant strain had multiple insecticide resistance to all 3 classes of insecticides. The highest levels of insecticide resistance were to pyrethroids, suggesting that the resistance resulted from selection with these insecticides in cotton. High levels of permethrin resistance were unstable and declined in plant bugs reared in the laboratory in the absence of any insecticide selection pressure. When reared in the laboratory, resistant bugs from Schlater had lower fecundity than a susceptible laboratory strain, and survival from egg hatch to adults was lower than in the susceptible strain. The distribution of insecticide resistance in tarnished plant bug populations from the Mississippi Delta is unknown, but control of populations with multiple insecticide resistance will be difficult. Compliance with the insecticide resistance management plan currently recommended for control of the tobacco budworm, Heliothis virescens (F.), in Arkansas, Louisiana, and Mississippi (by not using pyrethroids in cotton until July) is probably the best strategy for preventing the development of plant bug populations with multiple insecticide resistance in July and August.
137 citations
TL;DR: In laboratory bioassays, the pyrethroid insecticide, permethrin, repelled western com rootworm female beetles from treated com to lay eggs in untreated soybeans and demonstrated that western comRootworm damage to 1st-yr seed com could have been caused by pyrethoid use the previous summer in adjacent cornfields.
Abstract: In late June 1987, severe western com rootworm, Diabrotica virgifera virgifera LeConte, larval injury to com grown for seed production (inbred com) was observed within a 3-km 2 area near Piper City (Ford County), IL. The rootworm injury occurred in 6 fields that in the prior year had been planted to weed-free soybeans grown for seed production. The severe rootworm injury problem reoccurred in 1st-yr seed com in the same area in 1988 and to varying degrees in the years since (through 1994). Laboratory and field studies were initiated in 1987 to investigate several possible causes of the problem. Under simulated field soil temperature conditions, western com rootworm eggs from the Piper City population did not show evidence of the prolonged diapause trait. Although higher than expected oviposition took place in Piper City soybean fields, a large field study with staggered plantings of soybeans at Urbana, IL, <75 km away, confirmed earlier studies that few western com rootworm eggs are laid in weed-free soybean fields. Pyrethroid insecticides are routinely used in seed corn for com earworm, Helicoverpa zea (Baddie), control. In laboratory bioassays, the pyrethroid insecticide, permethrin, repelled western com rootworm female beetles from treated com to lay eggs in untreated soybeans and demonstrated that western com rootworm damage to 1st-yr seed com could have been caused by pyrethroid use the previous summer in adjacent cornfields.
127 citations
TL;DR: The use of these insect resistant BTK lines or equally efficacious commercial BTK cultivars in production agriculture should reduce insecticide applications for tobacco bud worm, boll worm, and cabbage looper while increasing farm profit and opportunities for the use of biological control.
Abstract: Transgenic cotton plants (BTK lines), carrying a gene construction that codes for the CryIA(b) or CryIA(c) 8-endotoxins from Bacillus thuringiensis variety kurstaki were evaluated in the field for resistance to naturally occurring tobacco bud worm, Heliothis virescens (F.), boll worm, Helicoverpa zea (Boddie), and cabbage looper, Trichoplusia ni (Hubner). Five BTK lines (each line was an independent insertion event) were evaluated in 1990 and 6 in 1991. Also 2 nontransgenic commercial cultivars, ‘Coker 312’, the explant source cultivar for the BTK lines, and an adapted cultivar, ‘Stoneville 453’, were evaluated. A split-plot design was used with lepidopteran control as the main plot and cotton lines as the subplots. Main plot treatments were weekly spray applications of insecticide for lepidopteran control during 8 or 9 wk of the growing season, or no insecticidal sprays for lepidopteran control. The season mean numbers of tobacco bud worm and boll worm larvae on plant mainstem terminals, flower buds and capsels, and the percentage of flower buds and capsels injured were lower for all BTK lines, in sprayed and unsprayed plots, than for the 2 nontransgenic cultivars. Averaged over both years, the season mean percent injury in plots of the unsprayed Coker 312 was ≈23% of the flower buds and 12% of the capsels. In unsprayed plots of the BTK lines, the season mean percent injury was ≈2.3 of the flower buds and 1.1 of the capsels. In unsprayed plots, the number of cabbage looper larvae and the amount of cabbage looper feeding injury to leaves also was lower on the BTK lines compared with the 2 nontransgenic cultivars. Using the recommended treatment thresholds for tobacco bud worm and boll worm of 8-15% injured flower buds, none of the BTK lines would have been treated, whereas injury in the 2 nontransgenic cultivars would have required multiple insecticide applications. Averaged over both years, the yield of unsprayed Coker 312 was 1,050 kg/ha and the average of all the unsprayed BTK lines was 1,460 kg/ha. Expression of these cryIA genes in Coker 312 cotton resulted in greater yield, 408 kg/ha, 38.8%, in the presence of lepidopteran pests. The use of these insect resistant BTK lines or equally efficacious commercial BTK cultivars in production agriculture should reduce insecticide applications for tobacco bud worm, boll worm, and cabbage looper while increasing farm profit and opportunities for the use of biological control.
124 citations
TL;DR: This glass-vial bioassay was used to determine insecticide resistance in 3 groups of tarnished plant bugs to 10 different insecticides and significant differences in resistance among adults were found.
Abstract: A glass-vial bioassay was developed for use in estimating resistance to insecticides in adult tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois). When laboratory reared insects of known age are used, the bioassay procedure requires that adults are not older than 10 d. Testing each sex separately was not required, and each glass-vial (treated on its inside with an insecticide) received a piece of green bean, Phaseolus vulgaris L., as food for the adults tested. Two or 3 adults were placed in each vial; mortality was determined after 24 h of exposure in the vial. The bioassay was used to determine insecticide resistance in 3 groups of tarnished plant bugs to 10 different insecticides. Significant differences in resistance among adults were found from the 3 groups with most of the insecticides. Data obtained with this glass-vial bioassay can be compared with data obtained from bioassays that use plant bugs collected from cotton, Gossypium hirsutum L., fields in which control with insecticides has been inadequate.
101 citations
TL;DR: The effects of a neem insecticide, containing azadirachtin (AZA) as the active ingredient, on fecundity, adult and egg mortality, and preference for neem-treated or untreated foliage on 2 predacious mite species, Phytoseiulus persimilis Athias-Henriot, and Amblyseius cucumeris (Oudemans).
Abstract: We tested the effects of a neem insecticide, containing azadirachtin (AZA) as the active ingredient, on fecundity, adult and egg mortality, and preference for neem-treated or untreated foliage on 2 predacious mite species, Phytoseiulus persimilis Athias-Henriot, and Amblyseius cucumeris (Oudemans). We also tested the effects of neem on egg, larval, and adult survival,, and on ovipositional preference for neem treated or untreated foliage, on the aphid predator Aphidoletes aphidimyza (Rondani). We found no significant differences in egg or adult mortality between treated and untreated mites for either species. For A. cucumeris , untreated females that contacted leaf disks and prey treated with 60 ppm AZA laid fewer egg after 48 h than females on untreated disks. In leaf-disk choice tests, significantly more P persimilis were found on untreated disks than those treated with 60 ppm after 24 h, and significantly more A. cucumeris were found on untreated disks than those treated with 60 ppm after 48 h. However, the number of eggs laid on treated versus untreated disks in these choice tests were not significantly different. For A. aphidimyza we found no significant differences in the percentage eclosion between neem-treated and untreated eggs. However, larval mortality ranged from 30 to 100% for 1st instars treated with neem, and adult emergence of treated larvae was significantly lower for 1st- and 3rd-instar A. aphidimyza compared with untreated controls. First and 3rd instars that acquired neem from contact with treated foliage or ingestion of treated aphids had greater mortality than larvae that were sprayed directly with neem solutions. No significant differences in the sex ratio of adults of the surviving neem treated and control larvae occurred. Adult A. aphidimyza exposed to 60 ppm AZA residues for 48 h in residual contact tests had significantly greater mortality (13%) compared with controls (5%). No significant differences in the number of eggs laid on treated and untreated mustard cabbage plants were apparent. We compared our results with previously published data on the effect of neem on beneficial arthropods.
95 citations
TL;DR: Chlorpyrifos resistance has evolved as a result of selection to other organophosphorus insecticides in Brazil and has never been reported before either in the United States or in Brazil.
Abstract: Resistance to chlorpyriphos-methyl, pirimiphos-methyl, and malathion was detected in lesser grain borer, Rhyzopertha dominica (F.), collected from 8 sites in the sates of Minas Gerais and Sao Paulo in Brazil and from 7 sites in northeast Kansas. These populations were screened for resistance by a discriminating concentration technique, which used vials impregnated with dried insecticide residues. Concentration-mortality regression lines were estimated to compare the resistance ratios for each insecticide and population. Malathion resistance ratios ranged from 2.1- to 12.2-fold at LC 50 ; pirimiphos-methyl resistance ratios ranged from 2.4- to 9.2-fold ; and chlorpyrifos-methyl resistance ratios ranged from 5.6- to 167.9-fold. Such high resistance levels to chlorpyrifos-methyl in lesser grain borer have never been reported before either in the United States or in Brazil. Because chlorpyrifos-methyl is not used against stored grain pests in Brazil, we conclude that chlorpyrifos resistance has evolved as a result of selection to other organophosphorus insecticides in Brazil.
92 citations
TL;DR: The results of this investigation suggest that D. noxia damage goes beyond the simple removal of photosyntheses from the plant and indicates a significant decrease in the capacity and efficiency of the primary photochemistry of photo system II.
Abstract: Plant entries that previously had tested resistant or susceptible to Russian wheat aphid, Diuraphis noxia (Mordvilko), were used to evaluate the effect of aphid feeding on leaf chlorophyll content and in vivo chlorophyll fluorescence induction kinetics. D. noxia feeding for 96 h caused significant reductions in chlorophyll a, chlorophyll b, and total chlorophyll content in susceptible wheat (‘Avon’, ‘TAM W-101’) and barley (‘Wintermalt’). Total chlorophyll content and constituent chlorophyll a and b levels were not significantly affected by D. noxia in resistant wheat (PI 366616, PI 372129) or barley (PI 366450) and in neither resistant (PI 386156) nor susceptible (‘Beagle 82’) critical. D. noxia infestation resulted in significant alterations of the primary fluorescence induction transients. When compared with non infested control plants, infested susceptible wheat and barley showed significantly increased non variable fluorescence (F) and decreased maximal fluorescence ( Fm ) and variable fluorescence ( Fv ). In contrast, values for these parameters did not differ significantly among the infested and non infested controls of resistant plants. When compared with control plants, the photochemical efficiency of photo system II ( F/Fm ) and the half-rise time from Fo to Fm (t1/2) were reduced significantly in the infested susceptible entries but remained relatively unchanged for the infested resistant cultivates. No significant differences between infested and non infested plants were observed in the measured chlorophyll fluorescence parameters for either the resistant or the susceptible critical, which implied a much different resistance mechanism(s) to D. noxia The results of this investigation suggest that D. noxia damage goes beyond the simple removal of photosyntheses from the plant. The substantial decrease in F/Fm following aphid infestation for the susceptible wheat and barley indicated a significant decrease in the capacity and efficiency of the primary photochemistry of photo system II.
86 citations
TL;DR: Two hyphomycetous fungi with potential as biocontrol agents were used in Bioassays against the Russian wheat aphid, Diuraphis noxia (Kurdjumov), and Aphids were significantly less susceptible to B. bassiana than to P. fumosoroseus, indicated by the lack of overlap among fiducial limits.
Abstract: Two hyphomycetous fungi with potential as biocontrol agents were used in Bioassays against the Russian wheat aphid, Diuraphis noxia (Kurdjumov). Dose-response assays were done using 5-7 concentrations of 2 isolates each of Beauveria bassiana (Balsamo) Vuillemin and Paecilomyces fumosomseus (Wize) Brown & Smith. A sensitive assay technique was developed in which adult aphids, 0-2 d of age, were sprayed with fungal spore suspensions on cut barley leaf sections. LC50 estimates were 91 and 282 spores per square centimeter for two B. bassiana isolates and 46 and 56 spores per square centimeter for two P. fumosoroseus isolates. Slopes ranged from 1.43 to 1.76. Aphids were significantly less susceptible to B. bassiana than to P. fumosoroseus , indicated by the lack of overlap among fiducial limits. LT50s varied inversely with dose for all 4 isolates and ranged from 4.6 d to 12.2 d for B. bassiana , and from 3.3 d to 12.2 d for P. fumosoroseus , depending on isolate and dose. In standardized screening assays, relative potencies ranged from 0.2 to 2.1 among 23 isolates of B. bassiuna , and from 0.3 to 3.7 among 14 isolates of P. fumosoroseus . Use of this assay method will facilitate studies of biotic and abiotic factors that influence Russian wheat aphid susceptibility to fungal infection in the laboratory and in the field.
79 citations
TL;DR: Exposure to δ-endotoxin of Bacillus thuringiensis tenebrionis has no statistically significant effect on survival, aphid consumption, development, or reproduction in beetles.
Abstract: We exposed larval and adult Hippodamia convergens (Guerin-Meneville), convergent lady beetle, to Myzus persicae (Sulzer), green peach aphid, reared on potatoes expressing δ-endotoxin of Bacillus thuringiensis tenebrionis . Because the toxin may be ingested by the aphid, the beetle may in turn be exposed to the toxin. However, we measured no statistically significant effect on survival, aphid consumption, development, or reproduction in beetles.
TL;DR: This study suggests that witllolding irrigation during peak flight of beetles, raising cutting height, and light application of aluminum sulfate in spring may help to reduce the severity of subsequent grub infestations.
Abstract: Cultural practices were manipulated before or during seasonal flights of Japanese beetle, Popillia japonica Newman, and masked chafers, Cyclocephala spp., to study effects on grub densities in tall fescue or Kentucky bluegrass turf. Masked chafer grubs were consistently smaller and less abundant in turf that had been treated with aluminum sulfate to reduce soil pH and in high-mown turf. High mowing or application of aluminum sulfate before beetle flights reduced total biomass of white grubs in tall fescue by as much as 55 and 77%, respectively. However, where spatial gradients in soil moisture occur, the positive response of grub populations to moisture may override effects of those treatments. Grub densities were not affected by spring applications of lime or urea or by aerification of plots before beetle flights. Plots that were irrigated during beetle flights incurred significantly higher densities of both P. japonica and Cyclocephala spp. grubs than did nonirrigated turf. The use of a 2,247- kg roller to compact the soil before beetle flights did not affect subsequent grub populations, and the roller was not effective for remedial control of 3rd instars in the fall. Application of organic fertilizers (composted cow manure or activated sewage sludge) resulted in significant increases in grubs of green June beetle, Cotinis nitida L., in 1 of 2 yr. Cultural practices may have general or species-specific effects on densities of white grubs. This study suggests that witllolding irrigation during peak flight of beetles, raising cutting height, and light application of aluminum sulfate in spring may help to reduce the severity of subsequent grub infestations.
TL;DR: A strain of German cockroach, Blattella germanica (L), collected from an institutional kitchen and cafeteria in Marietta, GA, in 1992, was examined for insecticide resistance, and results indicated that the broad spectrum of insecticides resistance observed in the Mariettta strain was the result of multiple resistance mechanisms.
Abstract: A strain of German cockroach, Blattella germanica (L.), collected from an institutional kitchen and cafeteria in Marietta, GA, in 1992, was examined for insecticide resistance. Topical insecticide bioassays revealed that the Marietta strain was resistant to bendiocarb (46-fold), cypermethrin (28-fold), propoxur (17-fold), permethrin (12-fold), and chlorpyrifos (7-fold). Pretreatment with the cytochrome P450 monooxygenase inhibitor, piperonyl butoxide, reduced the resistance level to the carbamates to varying degrees, but resulted in an increased resistance ratio to the pyrethroids. Similarly, the est erase inhibitor, S, S, S - tributyl phosphorotrithioate (DEF), partially reduced the resistance to bendiocarb while increasing the resistance ratio to permethrin. Detoxication enzyme assays revealed that activities of microsomal oxidases (aldrin epoxidase, phorate sulfoxidase, methoxyresorufin O -demethylase, p -chloro- N -methylaniline N -demetahylase, ethoxycoumarin O -deethylase), glutathione S -transferases (DCNB, CDNB, PNPA), hydrolases (general and carboxylesterase), and Cytochrome c reductase were 1.4- to IS-fold higher in the Marietta strain than in the susceptible strain. In addition, levels of cytochrome P450 and cytochrome b5 were 2.5- and 2.3-fold higher in the resistant strain than in the susceptible strain. The bimolecular rate constant for the inhibition of acetylcholinesterase by dichlorvos was similar in the resistant and susceptible strains. The results indicated that the broad spectrum of insecticide resistance observed in the Marietta strain was the result of multiple resistance mechanisms.
TL;DR: There was a nonlinear relationship between mean latent period and temperature with shorter mean latent periods at higher temperatures than at lower temperatures for both aster yellows phytoplasma strains and both ages of leafhoppers.
Abstract: Mean latent period and transmission rate of 2 strains bolt and severe ) of aster yellows photo plasma in nymph and adult aster leafhopper’s, Macrosteles quadrilineatus Forbes, were studied under controlled conditions at 15, 20, 25, and 30. There was a nonlinear relationship between mean latent period and temperature with shorter mean latent periods at higher temperatures (≈20-25 d) than at lower temperatures (≈40-80 d) for both aster yellows phytoplasma strains and both ages of leafhoppers. The proportion of leafhoppers that became vectors was significantly higher for bolt strain when leafhoppers acquired aster yellows phytoplasma as nymphs than as adults. However, there was no difference in the proportion that became vectors of the severe strain by the 2 age groups. Once leafhoppers became inoculative, the rate of transmission remained constant over their life spans when monitored by serial transfers at 48-h intervals. Increases in temperature and access time of leafhoppers increased tile proportion of leafhoppers that became vectors after feeding on bolt strain-infected plants. Also, the effect of aster yellows phytoplasma exposure on life spans of leafhoppers was studied at 4 temperatures. At 25 and 30, leafhoppers exposed to both aster yellows phytoplasma strains lived longer than those leafhoppers not exposed. Data can be used in an aster yellows epidemiological model to evaluate strategies for aster yellows management.
TL;DR: Factors affecting in vivo production of this entomopathogenic nematode in greater wax moth, Galleria mellonella, larvae are examined.
Abstract: The ‘Oswego’ strain of Heterorhabditis bacteriophom has been demonstrated to be effective against several soil-inhabiting pests. This study examined factors affecting in vivo production of this entomopathogenic nematode in greater wax moth, Galleria mellonella , larvae. Timing of emergence of infective juveniles and total production was studied in relation to inoculum rate and host crowding. Nematode establishment increased with increasing inoculum rate in the range of 20–500 infective juveniles per host. However, total production per host was insensitive to inoculum rate within this range. Average number of infective juveniles produced was 336,000 per host. Production within environmental chambers was not influenced by crowding of hosts within production dishes, or crowding among dishes within the chamber. There was some evidence of a crowding effect within production dishes on total production when nematodes were reared in moderately fluctuating ambient laboratory temperatures (mean = 23.8°C). Large, late stage wax moth larvae produced 567,000 infective juveniles per host, twice as many as produced from small, late stage, wax moth larvae. Infective juveniles were produced in at least 3 emergence cycles, but the greatest proportion emerged in the 1st production cycle (82%). Median emergence time from inoculation to the midpoint of the 1st production cycle was 17 d at an inoculation rate of 20 infective juveniles per host. Median emergence time was 1-2 d faster at doses of 200 infective juveniles per host. Median emergence time also varied with location within the environmental chamber.
TL;DR: In this paper, the authors found resistance to CryIC in a field population of diamondback moth from Hawaii that had been treated with B. thuringiensis subsp. kurstaki.
Abstract: Previous results have shown that diamondback moth, Plutella xylostella (L.), populations resistant to toxins from Bacillus thuringiensis subsp. kurstaki were susceptible to toxin CryIC. Use of commercial formulations of B. thuringiensis subsp. aizawai that contain CryIC has increased recently. Analysis of two commercial formulations by high pressure liquid chromatography showed that CryIC accounted for 26% of the CryI protein in the B. thuringiensis subsp. aizawai formulation, but did not occur in the B. thuringiensis subsp. kurstaki formulation. CryIAb was the most abundant CryI protein in the commercial formulations of B. thuringiensis subspp. aizawai and kurstaki. We found resistance to CryIC in a field population of diamondback moth from Hawaii that had been treated with B. thuringiensis subsp. aizawai . Leaf residue bioassays showed that, at 5 d after treatment with CryIC, LC50s for colonies derived from this population in 1993 and 1995 were ≈20 times greater than the LC50 for a susceptible laboratory colony. For a nearby population that had not been treated with B. thuringiensis subsp. aizawai , responses to CryIC did not differ significantly from those of the susceptible laboratory colony. Resistance to CryIAb was lower in a CryIC-resistant colony than in a CryIC-susceptible colony that had been selected with B. thuringiensis subsp. kurstaki . These results suggest that the gene(s) conferring resistance to CryIC segregate independently from the gene(s) conferring resistance to CryIAb. In contrast with previous results with colonies derived in 1989, resistance to B. thuringiensis subsp. kurstaki in a colony derived in 1993 from the same field population did not decline when exposure to B. thuringiensis stopped. Thus, stability of resistance is not necessarily a fixed character, even for a specific population and pesticide. Despite substantial resistance to CryIC and B. thuringiensis subsp. kurstaki , resistance to a spore-crystal formulation of B. thuringiensis subsp. aizawaiwas only 2- to 4-fold.
TL;DR: Comparisons of traditional whole-field integrated pest management with site-specific management for Colorado potato beetle, green peach aphid, Myzus persicae, and potato leafllopper revealed savings of 30-40% across a broad range of colonization pressures.
Abstract: Site-specific agriculture optimizes agricultural inputs by varying application rates to match within-field requirements. Two years of trials were conducted in rotated commercial potato fields to compare traditional whole-field integrated pest management with site-specific management for Colorado potato beetle, Leptinotarsa decemlineata (Say), green peach aphid, Myzus persicae (Sulzer), and potato leafllopper, Empoasca fabae (Harris). Additionally, the spatial dynamics of Colorado potato beetle populations subjected to whole-field integrated pest management were studied. Colorado potato beetle infestations mostly remained near field edges throughout the season. Highest densities for each life stage remained near the locations of the initial colonizing adults. Even if management thresholds were as low as the 3rd density decile, between 60 and 95% of the field area could be left untreated when the mean density exceeded the threshold. Site-specific management reduced insecticide inputs for the green peach aphid but not for potato leafhopper. Initial Colorado potato beetle colonization pressure, measured as egg mass density ≈7 d after crop emergence, was a significant covariable in determining season-long insecticide requirements. Analysis of covariance demonstrated that after accounting for this variable, site-specific management significantly reduced insecticide inputs compared with whole-field integrated pest management. Cumulative season-long Colorado potato beetle insecticide savings of 30-40% across a broad range of colonization pressures were observed.
TL;DR: Evaluation of the relative efficacy of fumigation and nonchemical alternatives for the control of drywood termites under conditions that simulated infestations in structures found both fumigant gases and mortality levels varied for some treatment techniques.
Abstract: Chemical and nonchemical methods for control of western drywood termites, Incisitermes minor (Hagen), were evaluated under conditions that simulated infestations in structures. The efficacy of excessive heat or cold, electrocution, microwaves, and 2 fumigants was evaluated. Termite mortality in artificially infested boards was 100% at 3 d after treatment for both fumigant gases. Heating the whole-structure or spot-applications using microwaves resulted in 96 and 90% mortality, respectively 3 d after treatment. Mortality levels 4 wk after treatment increased to 98% for heat and 92% for microwaves. Spot-applications of liquid nitrogen at 381.8 kg/m 3 achieved 100% mortality 3 d after treatment. However, for 122.7 and 57.3 kg/m 3 , mortality levels 4 wk after treatment were 99 and 87%, respectively. Mortality by spot-applications of electricity was 44% 3 d after treatment in the 1st test. Four weeks after treatment drywood termite mortality increased to 81%. In a 2nd electrocution test, using spotapplication techniques infrequently used in structures, mortality levels increased to 93% at 3 d and 99% at 4 wk after treatment. The distribution of termite survivors within the test building and test boards varied for some treatment techniques. For naturally infested boards, both fumigants exceeded 99% mortality. Use of heat and microwaves resulted in 100 and 99% mortality levels, respectively, 4 wk after treatment. Applications of liquid nitrogen resulted in mortality ≥ 99.8% at 381.8 and 122.7 kg/m 3 ; however, mortality for 57.3 kg/m 3 was significantly lower (74%). Mortality levels from electrocution were 89 and 95% 4 wk after treatment, respectively, in the 2 tests. Damage to test boards and the test building did occur. Six test boards were scorched during microwave treatment, 80% of test boards were damaged during electrocution, and visible signs of damage to the test building were noted for whole-structure heating. This study provides information for evaluation of the relative efficacy of fumigation and nonchemical alternatives for the control of drywood termite infestations in structures.
TL;DR: Results indicated that S. pyrioides reduced leaf photosynthesis in azalea by damaging palisade parenchyma which restricted gas exchange through stomata and reduced leaf chlorophyll content and photosynthetic capacity of remainingchlorophyll.
Abstract: Feeding injury caused by nymphs, males and females of the azalea lace bug, Stephanitis pyrioides (Scott), reduced rates of photosynthesis and transpiration in ‘Delaware Valley White’ azalea, Rhododendron mucronatum leaves. Females caused substantially more leaf feeding injury than males or nymphs. S. pyrioides was observed to insert stylets through stomata on the lower leaf surface and to feed almost entirely on upper palisade parenchyma tissue by piercing and removing cell contents. Lace bug feeding increased leaf stomatal resistance which indicated that gas exchange was restricted by stomatal closure. Feeding injury also reduced leaf chlorophyll content and photosynthetic capacity of remaining chlorophyll, but did not consistently affect chlorophyll a:b or specific leaf weight. Net leaf photosynthesis was negatively correlated with stomatal resistance and positively correlated with both chlorophyll content per unit leaf area and photosynthetic rate of remaining chlorophyll. These results indicated that S. pyrioides reduced leaf photosynthesis in azalea by damaging palisade parenchyma which restricted gas exchange through stomata and reduced leaf chlorophyll content and photosynthetic capacity of remaining chlorophyll.
TL;DR: Resistance declined from >500 times the resistance ratio to >74 times after 1 generation without selection pressure, remained ≈100 times after 3–6 generations and fell to 11 times after 8 generations and sex ratio remained the same over selection period.
Abstract: Laboratory selection of a strain of Spodoptera littoralis Boisduval with spore-crystal preparations of the Bacillus thuringiensis CryIC toxin for 14 generations resulted in resistance ratios from 10- to >500-fold resistance by using 2 different methods of selection. Partial cross-resistance was exhibited to CryID, CryIE, CryIAb toxins and to the parental strain B. thuringiensis aizawai 7.29. No cross-resistance occurred to CryIF. Resistance declined from >500 times the resistance ratio to >74 times after 1 generation without selection pressure, remained ≈100 times after 3–6 generations and fell to 11 times after 8 generations. Sex ratio remained the same over selection period. Pupal weights of the selected strain varied, but we observed no trend in these differences. Developmental time increased from 5 to 6 d for treated, resistant insects.
TL;DR: In laboratory and microplot consumption tests, spined soldier bug, Podisus maculiventris, ate at least as many Colorado potato beetle, Leptinotarsa decemlineata, eggs and larvae as did the twospotted stink bug, Perillus bioculatus (F).
Abstract: In laboratory and microplot consumption tests, spined soldier bug, Podisus maculiventris (Say), ate at least as many Colorado potato beetle, Leptinotarsa decemlineata (Say), eggs and larvae as did the twospotted stink bug, Perillus bioculatus (F) P maculiventris also remained in field microplots infested with Colorado potato beetle egg masses for slightly longer than did P bioculatus The 2 predators were equally effective at consuming egg masses, reducing densities of beetle larvae, and preventing potato defoliation in small field plots These results contrast with previous trials, in which P bioculatus had been more effective In laboratory trials, larger P maculiventris nymphs selected larger prey larvae, whereas P bioculatus nymphs did not discriminate by size of prey; thus, the relative effectiveness of the 2 predators may depend on the life stages of the prey that are present at the time of predator release
TL;DR: An automated system detected insects in all of the bins in which insects were found in grain samples and provided a good estimate of infestation level, and insects were most abundant in the top center of the wheat stored in bins, and only a few sensors in this area were needed for early detection.
Abstract: An automated method using cables with acoustical sensors was compared with the conventional grain sampling method for monitoring insect populations in wheat stored in 1 or 2 bins on each of 6 farms in Kansas. Seven flexible cables, each with 20 sensors 15 cm apart, were installed vertically in the grain mass along a transect across the diameter of the bin. A computer collected and stored the data. The automated system detected insects in all of the bins in which insects were found in grain samples and provided a good estimate of infestation level. Lesser grain beetle, Rhyzopertha dominica (F.) was the dominant species, and red flour beetle, Tribolium castaneum (Herbst), and rice weevil, Sitophilus oryzae (L.) were also detected. The number of times that insect sounds were detected was correlated with insect density in grain samples over a density range of 0-17 insects per kilogram. Insects were most abundant in the top center of the wheat stored in bins, and only a few sensors in this area were needed for early detection. Insects were found in grain samples at 5-37 sensor locations in any bin, but locations differed between bins. Insects were found in grain samples at a total of 50 sensor locations in 10 bins. Sensors will need to be distributed over a representative portion of a bin to determine insect infestation levels accurately.
TL;DR: The object of this study was to establish the relationship between a gradient of honey bees, Apis mellifera L., and fruit production of low bush blueberry, Vaccinium angustifolium Aiton and V. myrtilloides Michaux.
Abstract: The object of this study was to establish the relationship between a gradient of honey bees, Apis mellifera L., and fruit production of low bush blueberry, Vaccinium angustifolium Aiton and V. myrtilloides Michaux. Five hundred colonies of honey bees were grouped at one end of a blueberry culture, and pollinator counts as well as fruit sampling were made between 0.5 and 5.0 km from the hives, thus obtaining fruit production data from plots with many to no observed honey bees. Four parameters were estimated to assess blueberry production: seed set, fruit set, berry weight, and maturation rate. All parameters were significantly and positively correlated with an increase in the density of honey bees.
TL;DR: Characterization of abamectin resistance using residual and contact assays and by the use of the synergists piperonyl butoxide (PBO) and S,S, S, S,- tributyl phosphorotrithioate (DEF), indicated that differences may exist in the mechanisms used by different T. urticae populations to develop resistance.
Abstract: Populations of twospotted spider mite, Tetranychus urticae (Koch), from nurseries in California, Florida, the Canary Islands, and Holland that have been treated with abamectin for the control of Lyriomiza spp. and twospotted spider mites were evaluated for their susceptibility to abamectin using a leaf residual bioassay. Mite populations sampled during 1990-1992 varied greatly in their susceptibility to abamectin, with resistance ratios at the LC95 ranging from 0.5 to 175 in a I-d leaf residual assay. Resistance was correlated with the numbers of applications per year and years of use of abamectin. Based on correlation analyses, there may be differences in the development of resistance to abamectin in mites from California and mites from Holland. The data on number of applications per year show that resistance was not detected in California nurseries that had used the product <6 times per year or for 4 yr, whereas in Holland, resistance was detected in nurseries that had used the product 3 times per year or for 2 yr. Although functional resistance was detected in this laboratory bioassay, no field failures were observed. Characterization of abamectin resistance using residual and contact assays and by the use of the synergists piperonyl butoxide (PBO) and S, S, S,- tributyl phosphorotrithioate (DEF), indicated that differences may exist in the mechanisms used by different T. urticae populations to develop resistance.
TL;DR: Resistance mechanisms of a strain (PRAIAS) of northern house mosquito, Culex pipiens L., collected in Portugal in 1993, and highly resistant to organophosphates and carbamates, were investigated and found an insensitive AChE was the only resistance mechanism detected.
Abstract: Resistance mechanisms of a strain (PRAIAS) of northern house mosquito, Culex pipiens L., collected in Portugal in 1993, and highly resistant to organophosphates and carbamates, were investigated by comparing the resistance characteristics to 3 organophosphorous (temephos, chlorpyrifos, malathion) and 1 carbamate (propoxur) insecticides in the presence or absence of synergists; and by determining the possible occurrence of overproduced esterases or insensitive acetylcholinesterase (AChE). The reference strain MSE from southern France, with an insensitive AChE, was included in all analyses for comparison. For organophosphorous insecticides, resistance in PRAIAS was caused by an insensitive AChE and an increase in oxidative metabolism, although the 2nd mechanism has only a marginal effect. For propoxur, the insensitive AChE was the only resistance mechanism detected. Biochemical properties of both the French and Portuguese insensitive AChEs were similar. We cannot exclude the possibility that PRAIAS and MSE strains possess exactly the same insensitive AChE allele.
TL;DR: Factors that likely contribute to decreased performance of barrier sprays against ants include heavy irrigation, dense ground cover, exposure to direct sunlight, alkaline nature of the stucco and concrete surfaces, and extremely high temperatures.
Abstract: Insecticide was applied to the perimeter of homes and adjacent areas likely to be visited by Argentine ants, Iridomyrmex humilis (Mayr). Treatment configuration consisted of a 1.8- to 2.4-m-wide band of spray around the exterior of the structure. Margins of sidewalks and pathways and around stepping stones, bases of trees, potted plants, and garbage cans were sprayed with 1.2-to 1.8-m-wide bands. Based on monitoring with traps, significant and relevant control was achieved when the number of ants trapped post treatment declined at least 80%. Barrier sprays of 237 mg (AI)/m2 chlorpyrifos, 14.5 mg (AI)/m2 cyfluthrin and 67.2 mg (AI)/m2 cypermethrin provided >80% reductions in the number of ants trapped at 7 d. Chlorpyrifos provided >82% reductions for at least 30 d. The combination of cyfluthrin spray + granules provided >85% reductions in ant trap counts at day 7. Only the combination treatment provided >80% reductions at 60 d. Cypermethrin and permethrin sprays failed to provide >80% reductions for 30 d. Factors that likely contribute to decreased performance of barrier sprays against ants include heavy irrigation, dense ground cover, exposure to direct sunlight, alkaline nature of the stucco and concrete surfaces, and extremely high temperatures.
TL;DR: Field experiments were performed in 1993 and 1994 to establish varying densities of striped Acalymma vittatum (F.) and spotted, Diabrotica undecimpunctata howardi Barber, cucumber beetles in spring-planted cucumber plots, and to determine the incidence of bacterial wilt symptoms in each treatment to develop regression models to examine the relationship between beetle density and the severity ofacterial wilt disease.
Abstract: Field experiments were performed in 1993 and 1994 to establish varying densities of striped Acalymma vittatum (F.) and spotted, Diabrotica undecimpunctata howardi Barber, cucumber beetles in spring-planted cucumber plots, and to determine the incidence of bacterial wilt symptoms in each treatment. These data were used to develop regression models to examine the relationship between beetle density and the severity of bacterial wilt disease. Cucumber beetle numbers peaked during the first 2 wk after colonization of plants, with a rapid decline in numbers thereafter. Bacterial wilt symptoms were first observed 12-14 d after peak numbers of beetles were recorded. Critical point linear regression analyses of both year's data demonstrated a strongly linear and positive relationship between cucumber beetle density and the severity of wilt symptoms. No significant improvement was detected by fitting quadratic models. Beetle numbers recorded two weeks after colonization of plants provided the highest r 2 values when regressed on the percentage of wilted vines (final disease rating). Covariance analysis determined that regression slope values were not significantly different between years; therefore data for both years were pooled and a generalized model was developed. Substituting area under the disease progress curve values for the percentage of wilted vines per plant values resulted in a higher coefficient of determination (P = 0.0001, r2 = 0.73, slope = 70.3, intercept = 92.6), indicating that use of the progress curve, which accounts for disease development over time, provides a better regression fit than does use of a variable that reflects measurement of disease incidence at discrete intervals. The regression analyses also indicated that even low numbers (1 per plant) of beetles during the 1st few weeks after colonization of plants will result in wilt symptoms.
TL;DR: The characteristics of resistance to Bacillus thuringiensis Berliner in a strain of Colorado potato beetles, Leptinotarsa decemlineata (Say), and the toxicity ofCryIIIA toxin of transgenic potato plants containing the CryIIIA gene to each larval stage of susceptible and resistant strains of Colorado Potato beetle are examined.
Abstract: We have further examined the characteristics of resistance to Bacillus thuringiensis Berliner in a strain of Colorado potato beetles, Leptinotarsa decemlineata (Say). We compared the toxicity of CryIIIA toxin of transgenic potato plants containing the CryIIIA gene to each larval stage of susceptible and resistant strains of Colorado potato beetle. In bioassays, resistance ratios for resistant 2nd in stars were substantially higher than ratios for the other instars. Second instars from strains of Colorado potato beetles resistant to chemical insecticides were susceptible to transgenic potatoes. For all strains, 1st instars were sensitive to B. thuringiensis toxins, whereas 3rd instars were typically insensitive. Second and older instars of the B. thuringiensis -resistant strain had much higher survival compared with the susceptible strain after 96 h exposure to transgenic potatoes. Second and older resistant instars gained weight on transgenic plants, but at a significantly slower rate than on conventional foliage. Larvae of the susceptible strain typically lost weight when they fed on transgenic foliage. Adult beetles from the resistant strain experienced ≈;25% mortality in 14 d while feeding on transgenic potatoes, whereas the susceptible adults died.
TL;DR: The results support the hypothesis that the insect-to-host dissipation ratio increases at frequencies >2.45 GHz, and indicate that S. zeamais is more susceptible to pests.
Abstract: Insect mortality studies were performed with a high-power microwave source operating at a frequency of 10.6 GHz at power levels of 9–20 kW to irradiate samples of soft white wheat, Triticum aestivum (L.), infested with maize weevil, Sitophilus zeamais Motschulsky, and ground wheat infested with red flour beetle, Tribolium castaneum (Herbst). These pests are common internal and external feeders in stored products, respectively. Samples at various age intervals from egg to adult were exposed. The results support the hypothesis that the insect-to-host dissipation ratio increases at frequencies >2.45 GHz. Mean mortalities ≥93% occurred for all ages of S. zeamais and ≥94% for adults and larvae of T. castaneum for mean specific input energies of ≥5I J/g and 53 J/g, respectively, indicating that S. zeamais is more susceptible. Extrapolating the results to the cost of treating the product in bulk volume at a busbar electric energy cost of $0.05 per kW-h (3,600 kJ) indicates a unit cost for electric energy ranging only from 0.056 per bushel of wheat infested with S. zeamais to $0.139 per hundred weight of ground wheat infested with T. castaneum .
TL;DR: The overall potential of lufenuron as a bait toxicant is less than that of hexaflumuron, and baits treated with the nondeterrent concentrations of liffenuron caused only 50-80% mortality.
Abstract: Lethality, molting inhibitory effects, and feeding deterrence of 2 chitin synthesis inhibitors, hexaflumuron and lufenuron, were studied in a laboratory choice test using wood sawdust as feeding medium. Feeding deterrence of hexaflumuron in sawdust medium was lower than that observed in a previous study in which hexaflumuron-impregnated wooden blocks were used. The concentration threshold of hexaflumuron for feeding deterrence is high [>8,000 ppm for Coptotemes formosanus Shiraki, and >4,000 ppm for Reticulitermes flavipes (Kollar)], whereas ≈100% mortality was recorded 9 wk after exposure even at the lowest concentrations tested (125 ppm for C. formosanus and 31.3 ppm for R. flavipes ). Feeding deterrence of lufenuron was observed at lower concentration intervals (1,000-2,000 ppm and 50-100 ppm for C. formosanus and R. flavipes , respectively) than hexaflumuron, but baits treated with the nondeterrent concentrations of lufenuron caused only 50-80% mortality. even after 9 wk of exposure. The overall potential of lufenuron as a bait toxicant is less than that of hexaflumuron.