Trunk injection to control Xylosandrus germanus (Coleoptera: Curculionidae) in topworked apple trees

Xylosandrus germanus (Blandford) is an invasive species of ambrosia beetle known to attack apple trees in North America. Xylosandrus germanus are attracted to ethanol produced by stressed and injured trees and can be a serious problem when grafting a new cultivar onto established fruit trees (topworking). The objective of this study was to evaluate the efficacy of 2 insecticides (emamectin benzoate and azadirachtin) and injection timing (fall and spring) on their ability to control X. germanus colonization in apple trees with simulated topworking. Our study shows evidence that both emamectin benzoate and azadirachtin injections can reduce X. germanus infestations; however, our results were inconsistent. The timing of injections influenced X. germanus, with spring injected azadirachtin being more effective than fall injections. Residue analyses of emamectin benzoate and azadirachtin showed the presence of residues in woody tissue comparable to those found in leaves.

Systemic insecticides for control of stem gall wasp in highbush blueberry

The gall wasp, Hemadas nubilipennis Ashmead, is a pest of highbush and lowbush blueberry and can pose a challenge to control with foliar sprays due to adult activity being during bloom and because larval development is within plant tissues. We hypothesized that systemic insecticides that move within the blueberry vascular system would reach areas where H. nubilipennis eggs are laid, causing larval mortality. Three application methods, crown injection, soil drench, and foliar spray were applied to potted 'Jersey' blueberry bushes at 50% and 100% rates to quantify systemic residue concentrations in shoots and leaves. Additionally, systemic insecticides were evaluated for control of gall wasps using single-shoot bioassays and measuring larval mortality at 0.01%, 0.1%, 1%, and 10% of field rate provided within a floral pick. Systemic insecticides tested in both studies included imidacloprid, flupyradifurone, and spirotetramat. The potted bush residue study determined that insecticides moved from three tested sites of entry: the roots, crown cavity, and foliage. Results from the shoot bioassays found that the mean percent larval survival of H. nubilipennis was negatively correlated with the concentration of AI detected in galls. Imidacloprid and spirotetramat were found to have the greatest potential for control of H. nubilipennis due to mortality in the shoot bioassays and similar residue concentrations in the potted bush studies to shoot bioassays. Future research should evaluate systemic insecticides applied in highbush blueberry plantings for control of H. nubilipennis using the bioassay mortality assessment method developed in this study.

Trunk injection delivery of dsRNA for RNAi-based pest control in apple trees

BACKGROUND

RNA interference (RNAi) is a promising new approach for controlling insect pests without the use of synthetic pesticides. Trunk injection is a delivery system for woody plants that harnesses the vascular system of the tree to transport materials to the tree canopy. Full size apple trees were injected with double-stranded RNA (dsRNA), and season-long leaf samples were taken to measure the vascular mobility and temporal persistence of dsRNA, using quantitative reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS

The qRT-PCR results revealed that the quantities of dsRNA in the apple leaves of treated trees were significantly greater than those in the leaves of untreated trees for both 2019 and 2020 studies. The peak dsRNA concentration in 2019 was 242 pg/30 mg of leaf tissue, and in 2020 was 16.4 pg/30 mg. The persistence of dsRNA in the apple tree canopy in 2019 was at least 84 days, and in 2020 was at least 141 days.

CONCLUSIONS

The highest mean measurement of dsRNA on a single date in 2019 was 242 pg, which is approximately equivalent to 8 ng/1 g leaf tissue. The projection using the highest replicate concentration from the same date is approximately equivalent to 27 ng/1 g leaf tissue, which may be sufficient to be considered biologically active. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Curative Activity of Insecticides Used to Control Spotted-Wing Drosophila (Diptera: Drosophilidae) in Tart Cherry Productions

Spotted-wing drosophila (Drosophila suzukii Matsumura) is a major pest of soft-skinned fruit and due to the low infestation tolerance for marketable fruit, growers take preventive actions to hinder spotted-wing drosophila damages. Insecticides application is one of the measures taken by growers. Although intensive spraying programs have been used to manage spotted-wing drosophila, its early infestation, rapid reproduction, and vast range of host have caused damage to still occur in fruit, including tart cherries, Prunus ceraus (Linnaeus). Therefore, there is a merit for information on insecticide's curative activity to understand whether sprays manage spotted-wing drosophila individuals within infested fruit. Tart cherry fruit were exposed to spotted-wing drosophila adults for 3 d. After this infestation period, insecticides were applied 1 and 3 d later. Small larvae, large larvae, and pupae were counted 9 d after initial infestation. A parallel set of insecticide-treated tart cherries were subjected to residue analysis. Phosmet and spinetoram were able to reduced live spotted-wing drosophila counts compared with the control at all life stages and insecticide application times, whereas zeta-cypermethrin, acetamiprid, and cyantraniliprole were less consistent in reducing spotted-wing drosophila numbers. Chromobacterium subtsugae demonstrated no curative action. Residue analysis demonstrated that zeta-cypermethrin residues mostly remained on fruit surface. Small portions of phosmet, spinetoram, and cyantraniliprole were able to penetrate fruit surfaces and move into subsurface tissues. Acetamiprid was the only compound which >47% penetrated into the fruit subsurface consistently across both years. Curative activity demonstrated in this study can provide additional tactics for spotted-wing drosophila management in tart cherry Integrated Pest Management (IPM) programs.

Organic Control of Pear Psylla in Pear with Trunk Injection

Simple Summary

Organic pear production is challenged, in part, by short lived effects of biopesticides when applied as foliar sprays. Trunk injection may enhance their performance by delivering the biopesticides directly to the vascular system of the tree, right where pear psylla feed. The objective of this study is to compare trunk injections to foliar sprayed applications of two insecticides, azadirachtin and abamectin, on their ability to control pear psylla in pear trees. The azadirachtin and abamectin trunk injected treatments performed equally or better than two foliar applications in the control of the pear psylla. The trunk injected trees from the first season provided a moderate level of control into the second season, one year after the injections. This study suggests that trunk injection is a superior delivery system for biopesticides used in organic pear production.

Abstract

Organic production of pears is challenging in part because OMRI (Organic Materials Review Institute) approved biopesticides are short lived when applied as foliar sprays. Trunk injection is an alternative method of insecticide delivery that may enhance the performance of biopesticides for control of pear psylla. The objective of this study is to compare the efficacy of azadirachtin and abamectin in the control of pear psylla using two different application methods, airblast sprayer and trunk injection. Trunk injections of azadirachtin and abamectin were compared to airblast applications of equal labeled rates on 33-year-old Bartlett Pear trees (Pyrus communis L., var “Bartlett”). The azadirachtin and abamectin trunk injected treatments performed equally or better than the two airblast applications in the control of the pear psylla. The trunk injected trees from the first season provided a moderate level of control into the second season, one year after the injections. This study suggests that trunk injection is a superior delivery system for biopesticides used in organic pear production.

Metabolic mechanisms of indoxacarb resistance in field populations of Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae)

Synergism and metabolic studies were conducted to identify the resistance mechanism against indoxacarb in two Choristoneura rosaceana (Harris) field populations compared to a susceptible population. The synergism study was carried out using diet incorporation bioassay for indoxacarb and the three synergists PBO, DEM, and DEF. The metabolic study consists of indoxacarb in vitro reaction with fifth instar larvae 12,000 g midgut supernatant or with pre-inhibited (in vivo by the esterases inhibitor DEF) fifth instar larvae 12,000 g midgut supernatant at different incubation times. In both susceptible and cherry populations, only DEF significantly synergized indoxacarb with a synergism ratio (SR) of 6.5 and 22.6-fold respectively indicating an involvement of esterases in the both populations. In the apple population, all synergists PBO, DEM, and DEF significantly synergized indoxacarb with SR of 9.6, 7.7, and 285.6-fold respectively indicating a complex resistance case with the possible involvement of all three metabolic resistance mechanisms with the central role of esterase enzymes. In vitro, the indoxacarb (DPX-JW062) was very rapidly metabolized within 5 min into small molecules in the lower portion of the metabolic pathway when it reacted with the midgut supernatant of each population. None of the metabolites in the upper portion of the metabolic pathway were detected at any incubation time including the potent sodium channel blocker DCJW metabolite. The two field populations showed significantly higher rates of metabolism of DPX-JW062 compared to the susceptible population at five min of incubation and that may explain the presence of indoxacarb resistance. In the second part of the in vitro study, the bio-transformation of DPX-JW062 was remarkably decreased when it reacted with the pre-inhibited (by DEF) midgut supernatant of each population. Additionally, the degradation of metabolites in the upper portion of the metabolic pathway remarkably decreased, which resulted in accumulation of DCJW and MP819 metabolites. The accumulation of DCJW metabolite under the pre-inhibited midgut supernatants treatment provided a persuasive explanation of the synergistic impact of esterase inhibitor DEF on indoxacarb in C. rosaceana.

Leaching of insecticides used in blueberry production and their toxicity to red worm

Soil columns were collected from a blueberry field, and insecticide solutions were allowed to leach through these columns. Insecticides from four different chemical classes were applied at two different rates: the concentration at which the insecticides wash off blueberries under rainfall conditions and the labeled field rate at which they are sprayed. The soil columns were divided into thirds; top, middle and bottom. Soil bioassays using Eisenia foetida Savigny, as an indicator species, were set up to determine the toxicity of the insecticides at a top, middle and bottom layer of the soil column. The mass of E. foetida was also measured after the bioassay experiment was completed. The concentrations at which insecticides wash-off of blueberries from rainfall were not lethal to E. foetida. In order to support mortality data, insecticide residues were quantified in the soil layers for each insecticide. Under field rate leaching conditions, carbaryl showed the high levels of toxicity in the top and middle layers of soil suggesting that it has the highest risk to organisms from leaching. This study will help blueberry growers make informed decisions about insecticide use, which can help minimize contamination of the environment.

Residual Toxicity of Insecticides to Neoseiulus fallacis (Acari: Phytoseiidae) in Apples

Neoseiulus fallacis (Garman) is a predatory mite that is common in apple orchards and distributed throughout North America. However, N. fallacis may be susceptible to pesticides used for the management of crop pests. This study aimed to evaluate the temporal effects of commonly used insecticides on N. fallacis survival. Neoseiulus fallacis adults were exposed to field-aged residues, and mortality and lethal time were measured over 96 h of exposure. Carbaryl caused high mortality to N. fallacis and the shortest lethal time values (LT50), followed by spinetoram, with moderate lethal time values. Esfenvalerate, acetamiprid, chlorantraniliprole, and novaluron showed little to no lethality to N. fallacis following exposure to dry field-aged residues. The results of this study provide important field-relevant knowledge that is often void from laboratory-based studies, which can aid integrated pest management (IPM) decision-makers in apple production systems.

Insecticide dose and seasonal timing of trunk injection in apples influence efficacy and residues in nectar and plant parts

BACKGROUND

Trunk injection is an established method for delivering pesticides in ornamental and shade trees, but further research is needed to determine efficacy and pollinator safety in tree fruit crops. Apple trees were injected in 2013 and 2014 with the insecticides emamectin benzoate, imidacloprid, dinotefuran, spinosad, chlorantraniliprole, or abamectin. Additional emamectin benzoate and imidacloprid injections were performed in the spring and fall of 2015. Nectar and pollen were sampled in the following spring to compare the effects of application timings on insecticide loading into flowers.

RESULTS

Neonicotinoids reduced Empoasca fabae density in the field. Emamectin benzoate, chlorantraniliprole, and abamectin resulted in moderate to high mortality and reduced Choristoneura rosaceana feeding in bioassays. Imidacloprid was not detected in nectar or pollen when injected in the spring, and was detected at 0.39 ng g^-1 in pollen when injected the previous fall. Emamectin benzoate was not detected in nectar or pollen when injected the previous fall, and was detected at 7.36 ng g^-1 (nectar) and 1.15 ng g^-1 (pollen) when injected in the spring.

CONCLUSIONS

This study identified a broader list of possible trunk-injectable pesticides for apple trees. This study also shows that managing the seasonal timing of injection can reduce the risk of insecticide exposure to pollinators. © 2018 Society of Chemical Industry.

Seasonal and Cross-Seasonal Timing of Fungicide Trunk Injections in Apple Trees to Optimize Management of Apple Scab

To optimize the number and timing of trunk injections for season-long control of apple scab (Venturia inaequalis), we evaluated 1 to 2 and 4 seasonal and cross-seasonal injections of potassium phosphites and synthetic fungicides and quantified residues in leaves and fruit. Phosphites accumulated in the canopy at the highest concentrations, aligned well in time with scab suppression, and gave better leaf scab control of 41.8 to 73.5% than propiconazole (16.9 to 51.5%) or cyprodinil + difenoconazole (5.4 to 17.4%). More injections of phosphites controlled leaf scab better than fewer (23.7% versus 48.2%), and more fungicide injections resulted in 21.9 to 51.1% better leaf scab control than fewer. Leaf scab control with phosphites was only 3.2 to 13.9% better with 4 cross-seasonal compared with 4 seasonal injections, while 1 to 2 seasonal compared with 1 to 2 cross-seasonal injections improved scab control only for 4.2 to 22.1%. On shoots, injected phosphites provided comparable or for 4.4 to 10.5% and 22.3 to 41.4% better scab control than spray standards. On fruit, injected phosphites slightly improved control compared with sprayed phosphites or the sprayed fungicide standard (33.4 to 40.8%). Two seasonal injections of phosphites controlled shoot scab 5.7% better than 9 spray applications. Five sprays of cyprodinil + difenoconazole controlled scab better than their injections. Fruit residues of phosphites reached 2.8 ppm and declined in all treatments except in 2 seasonal injections and phosphite sprays. Cyprodinil and difenoconazole fruit residues reached 0.02 and 0.07 ppm and declined sharply toward the end of the season. These were far below the United States, Codex, and EU MRL-s of 1, 0.8, and 0.5 ppm for difenoconazole, and 1.7, 2, and 1 ppm for cyprodinil, respectively.

Spatial and temporal distribution of trunk-injected imidacloprid in apple tree canopies

BACKGROUND

Pesticide use in orchards creates drift-driven pesticide losses which contaminate the environment. Trunk injection of pesticides as a target-precise delivery system could greatly reduce pesticide losses. However, pesticide efficiency after trunk injection is associated with the underinvestigated spatial and temporal distribution of the pesticide within the tree crown. This study quantified the spatial and temporal distribution of trunk-injected imidacloprid within apple crowns after trunk injection using one, two, four or eight injection ports per tree.

RESULTS

The spatial uniformity of imidacloprid distribution in apple crowns significantly increased with more injection ports. Four ports allowed uniform spatial distribution of imidacloprid in the crown. Uniform and non-uniform spatial distributions were established early and lasted throughout the experiment. The temporal distribution of imidacloprid was significantly non-uniform. Upper and lower crown positions did not significantly differ in compound concentration. Crown concentration patterns indicated that imidacloprid transport in the trunk occurred through radial diffusion and vertical uptake with a spiral pattern.

CONCLUSION

By showing where and when a trunk-injected compound is distributed in the apple tree canopy, this study addresses a key knowledge gap in terms of explaining the efficiency of the compound in the crown. These findings allow the improvement of target-precise pesticide delivery for more sustainable tree-based agriculture.

Lethality of reduced-risk insecticides against plum curculio (Coleoptera: Curculionidae) in blueberries, with emphasis on their curative activity

BACKGROUND

Historically, management of plum curculio, Conotrachelus nenuphar (Herbst), in highbush blueberries has focused on post-bloom broad-spectrum insecticide applications targeting the adults. Here, the efficacy of different classes of insecticides against various stages of C. nenuphar was compared, and a prebloom treatment with the chitin synthesis inhibitor novaluron in combination with a post-bloom insecticide application was tested.

RESULTS

Novaluron decreased the number of oviposition scars and eggs on fruit and reduced larval emergence by >60% when applied prebloom. Post-bloom applications of the oxadiazine indoxacarb and the organophosphate phosmet, but not the neonicotinoid acetamiprid, showed significant adulticidal activity. The neonicotinoids acetamiprid and thiamethoxam and phosmet showed significant curative activity on C. nenuphar larvae when applied topically to infested fruit, whereas the pyrethroid fenpropathrin, indoxacarb and novaluron were weaker curative agents. Residue profiles showed that acetamiprid and phosmet residues had the highest levels while fenpropathrin and novaluron had the lowest levels of fruit penetration.

CONCLUSIONS

In blueberries, novaluron showed anti-ovipositional/ovicidal activity, indoxacarb and phosmet showed adulticidal activity, while the neonicotinoids and phosmet showed best curative (larvicidal) control on C. nenuphar. A prebloom novaluron application in combination with a post-bloom treatment with an adulticidal/larvicidal insecticide is recommended for optimal multi-life-stage management of C. nenuphar. © 2013 Society of Chemical Industry.

Rainfastness of insecticides used to control Japanese beetle in blueberries

Field-based bioassays were used to determine the relative impact of rainfall on the relative toxicity of four insecticides, phosmet, carbaryl, zeta-cypermethrin, or imidacloprid, from different chemical classes on adult Japanese beetles, Popillia japonica Newman, in highbush blueberries, Vaccinium corymbosum L. Bioassays were set up 24 h after spraying occurred and Japanese beetle condition was scored as alive, knockdown or immobile 1, 24, and 48 h after bioassay setup. All insecticides were significantly more toxic than the untreated control and zeta-cypermethrin consistently had the greatest toxic effect against the Japanese beetles. All insecticides experienced a decrease in efficacy after simulated rainfall onto treated blueberry shoots, although the efficacy of zeta-cypermethrin was the least affected by rainfall. This study will help blueberry growers make informed decisions on when reapplications of insecticides are needed in the field with the aim of improving integrated pest management (IPM).

Rainfastness and residual activity of insecticides to control Japanese beetle (Coleoptera: scarabaeidae) in Grapes

Field-based bioassays and residue profile analysis were used to determine the relative toxicity, rainfastness, and field degradation over time of five insecticides from five insecticide classes on adult Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), in grapes, Vitis labrusca L. Bioassays assessed Japanese beetle condition as alive, knockdown, or immobile when exposed for 24 h or 7-d field-aged residues of phosmet, carbaryl, bifenthrin, thiamethoxam, or indoxacarb after 0, 12.7, or 25.4 mm of rain had been simulated. We found that the two most toxic insecticides to Japanese beetle were phosmet and carbaryl, followed by bifenthrin, thiamethoxam, and then indoxacarb. The efficacy of phosmet decreased because of rainfall, but not because of field aging. The efficacy of carbaryl decreased because of rainfall and field aging. The efficacies of bifenthrin and thiamethoxam were not affected by rainfall but decreased because of field aging. The efficacy of indoxacarb was not affected by rainfall or field aging. This study will help vineyard managers make informed decisions on when reapplications of insecticides are needed with the aim of improving integrated pest management programs.

Plum curculio (Coleoptera: Curculionidae) adult mortality and associated fruit injury after exposure to field-aged insecticides on tart cherry branches

Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), adults were exposed to field-aged residues of thiamethoxam, acetamiprid, thiacloprid, indoxacarb, or azinphos-methyl on tart cherry, Prunus cerasus L. variety Montmorency. At 1, 3, 7, and 14 d postapplication, fruit were sampled for chemical residues, and bioassays were used to assess beetle mortality and plant tissue injury. Azinphos-methyl had lethal activity within 1 d of exposure at all postapplication intervals and significant fruit protection extended to 14 d postapplication. All of the neonicotinoids had lethal activity at 3 d posttreatment, with acetamiprid activity extending to 7 d. Antifeedant and oviposition deterrent effects were seen with thiamethoxam and thiacloprid; damage incidence was significantly reduced in the absence of significant beetle mortality or intoxication. Thiamethoxam and acetamiprid penetrated into leaf and fruit tissue and were detected in the interior tissues at 14 d postapplication, but interior thiacloprid residues were not detected after day 1. Indoxacarb provided some fruit protection out to 7 d postapplication, and 14-d-old residues intoxicated beetles, but the slow action of this compound allowed significant damage to occur before beetles were incapacitated. Indoxacarb was only detected as a surface residue after the first day postapplication. These data on the plant-insect-chemistry interactions will support use and management decisions as compounds with acute contact activity are phased out.

Curative activity of insecticides on Rhagoletis pomonella (Diptera: Tephritidae) in apples

Field-based experiments were used to determine the lethal activity of insecticides on apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), eggs and larvae in apple (Malis spp.) fruit. The organophosphates azinphosmethyl and phosmet and the neonicotinoids thiacloprid, acetamiprid, clothianidin, and thiamethoxam showed significant curative activity on the apple maggot postinfestation, when applied topically to apple fruit 24 h postharvest. Of the compounds tested, only phosmet showed significant curative activity on apple maggot when applied 14 d postharvest. The pyrethroid esfenvalerate, oxadiazine indoxacarb, anthranilic diamide chlorantraniliprole, and spinosyns spinosad and spinetoram did not show activity on apple maggot eggs and larvae in fruit. Residue profiles showed that for most compounds, the majority (>85%) of residues were found in the skin and the outside 2 mm of the apple flesh. For the neonicotinoid compounds, however, substantial portions of residues were found to penetrate in and beyond the outer flesh regions, and the total flesh residue recoveries were generally greater than those from the skin. Residues of azinphosmethyl and phosmet were detected in all three flesh regions, with the largest proportions recovered from the skin.

Curative activity of insecticides against plum curculio (Coleoptera: Curculionidae) in tart cherries

Tart cherry, Prunus cerasus L. variety Montmorency, fruit were infested with plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), and treated with insecticides to target late instars, neonates, and eggs. The organophosphates azinphos-methyl and phosmet and the neonicotinoid thiamethoxam reduced larval emergence rates by >90% for all life stage targets; after >30 d, few surviving larvae were found inside fruit. Acetamiprid and thiacloprid also had curative activity and yielded >75% reductions in emergence and few surviving larvae in the fruit after >30 d. The juvenile hormone analog pyriproxyfen reduced larval emergence, but 66% of fruit that was treated to target late-instars still had live larvae inside of them after >30 d. Novaluron, chlorantraniliprole, and esfenvalerate had no curative activity. Indoxacarb had limited curative activity, and all targeted life stages had larval emergence. Internal and external residues were analyzed and are discussed in relation to their penetration and curative potential. The curative activity of azinphos-methyl has played an important role in meeting federal standards for infestation-free tart cherries at processing. Regulatory changes are eliminating the use of this compound, and new integrated pest management programs for plum curculio will need to address the loss of azinphos-methyl's curative activity.

Lethal and sublethal activities of imidacloprid contribute to control of adult Japanese beetle in blueberries

Field-based bioassays and residue profile analysis were used to determine the relative importance of lethal and sublethal effects of imidacloprid on adult Japanese beetle, Popillia japonica Newman, in blueberries, Vaccinium corymbosum L. Field-based bioassays assessed adult mortality and knockdown, and fruit and leaf injury from Japanese beetles exposed to 4-h and 7-d field-aged residues of imidacloprid, and the conventional insecticides azinphosmethyl and esfenvalerate. Azinphosmethyl and imidacloprid caused high levels of mortality when beetles were exposed to blueberry shoots with ripe fruit 4 h postapplication, and all compounds protected blueberry fruit and foliage from beetle feeding. Azinphosmethyl and esfenvalerate caused significant Japanese beetle mortality when adults were exposed to blueberry shoots 7 d postapplication, whereas imidacloprid residues caused effects that protected leaves, although not of ripe fruit. When beetles were exposed to shoots with immature green fruit, relatively more leaf feeding and mortality were observed, suggesting that earlier treatment timings may be most effective for systemic neonicotinoids. Japanese beetle mortality was highly correlated with imidacloprid fruit and leaf surface residues, whereas sublethal feeding deterrent effects were observed after the surface residues diminished. The value of the plant-insect-chemistry model for describing the spatial and temporal dimensions of insecticide modes of activity is discussed in terms of optimizing crop protection.

Novel life stage targets against plum curculio, Conotrachelus nenuphar (Herbst), in apple integrated pest management

In this study the authors employed the plant-insect-chemistry (PIC) triad to investigate two novel life stage targets against the plum curculio (PC), Conotrachelus nenuphar (Herbst), in apple integrated pest management (IPM). Laboratory treated apple bioassays were used to determine if the insect growth regulator (IGR) insecticides novaluron and tebufenozide have physiological effects on PC larvae following adult exposure. Curative activity bioassays were conducted for IGR, neonicotinoid, oxidiazine and organophosphate insecticides on PC larvae post-infestation, and fruit penetration profiles of insecticides were developed. The results revealed that novaluron exhibits activity on PC larvae via vertical transmission following exposure of mated females to treated substrate. Surface treatments of azinphos-methyl, thiacloprid and thiamethoxam to preinfested fruit resulted in significant reductions in larval emergence. For all compounds, 50% or more of the total recovered active ingredient was from apple skin, and for azinphos-methyl, indoxacarb and thiamethoxam it was greater than 80%. For azinphos-methyl, novaluron, methoxyfenozide and thiacloprid, however, active ingredient was recovered from every section of the apple, from skin to core. Implications for twenty-first century IPM are discussed.

Contaminants in fishes from Great Lakes-influenced sections and above dams of three Michigan rivers. II: Implications for health of mink

Populations of mink (Mustela vison) have declined in many areas of the world. Such declines have been linked to exposures to synthetic, halogenated hydrocarbons. In the Great Lakes region, mink are fewer in areas along the shore of the Great Lakes and their tributaries where mink have access to fish from the Great Lakes. Recently, there has been discussion of the relative merits of passage of fishes around hydroelectric dams on rivers in Michigan. A hazard assessment was conducted to determine the potential for adverse effects on mink, which could consume such fishes from above or below dams on the rivers. Concentrations of organochlorine insecticides, polychlorinated biphenyls (PCBs), 2,3,7,8-tetrachlordibenzo-p-dioxin equivalents (TCDD-EQ), and total mercury were measured in composite samples of fishes from above or below hydroelectric dams on the Manistee and Muskegon Rivers, which flow into Lake Michigan, and the Au Sable River, which flows into Lake Huron. Concentrations of organochlorine insecticides, PCBs, and TCDD-EQ were all greater in fishes from below the dams than those from above. Concentrations of neither organochlorine insecticides nor mercury in fishes are currently a risk to mink above or below the dams. All of the species of fishes collected from downstream of the dams contained concentrations of PCBs and TCDD-EQ, which represent a hazard to mink. The hazard index for PCBs was less than one for the average of all species from the upstream reaches of the Manistee and Au Sable Rivers, but not the Muskegon. The hazard index (concentration in fish/NOAEC) was greater than 1 for all of the species collected from below the dams, in all three rivers. The greatest hazard index was observed for carp (Cyprinus carpio) downstream on the Muskegon River. Because the concentrations of PCBs used in the hazard assessment were corrected for relative toxic potencies, the hazard ratios based on PCBs should be similar to those based on TCDD-EQ. This was found to be true. Thus, either total PCBs or TCDD-EQ could be used as the critical toxicant in the hazard assessment. However, if uncorrected concentrations of PCBs, expressed as Aroclors, were used in the hazard assessment, the toxicity of the weathered mixture would have been underestimated by approximately five-fold, and, in that instance, TCDD-EQ would be the critical contaminant for the hazard assessment.(ABSTRACT TRUNCATED AT 400 WORDS)

Contaminants in fishes from Great Lakes-influenced sections and above dams of three Michigan rivers. I: Concentrations of organo chlorine insecticides, polychlorinated biphenyls, dioxin equivalents, and mercury

Fishes of the Great Lakes contain hazardous chemicals such as synthetic halogenated hydrocarbons and metals. These fish can move from the lakes into the Great Lakes tributaries of Michigan. In doing so, they transport concentrations of contaminants which may represent a risk to wildlife. Concentrations of mercury (Hg), total polychlorinated biphenyls (PCBs), 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ), total DDT complex, aldrin, endrin, dieldrin, heptachlor, heptachlor epoxide, lindane, hexachlorobenzene, cis-chlordane, oxychlordane, endosulfan-I, methoxychlor, trans-chlordane, and trans-nonachlor were determined in composite samples of fishes from above and below Michigan hydroelectric dams, which separate the fishes which have access to the Great Lakes from fishes that do not. Mean concentrations of total PCBs, TCDD-EQ, DDT, and most of the other pesticides were greater in composite samples of six species of fishes from below than above the dams on the Au Sable, Manistee, and Muskegon Rivers. Concentrations of mercury, were the same or greater above the dams than below. However, this difference was statistically significant only on the Au Sable. Mercury concentrations ranged from less than 0.05 mg/kg to 0.73 mg Hg/kg, ww. Total concentrations of PCBs ranged from 0.02 to 1.7 mg/kg, ww. Concentrations of 2,3,7,8-tetrachlordibenzo-p-dioxin equivalents varied among fishes and locations. The concentrations of TCDD-EQ ranged from 2.4 to 71 micrograms/kg, ww, with concentrations in carp being the greatest. Concentrations of TCDD-EQ were greater than the concentrations which would be expected to occur, due solely to the presence of polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and technical mixtures of PCBs.