Toxicity and kinetics of spinosad in different developmental stages of the endoparasitoid Hyposoter didymator (Hymenoptera: Ichneumonidae) and its host Spodoptera littoralis larvae (Lepidoptera: Noctuidae) (original) (raw)
Related papers
Biocontrol Science and Technology, 2005
Laboratory studies were performed on the lethal and sublethal effects of spinosad on three important species of parasitoids attacking Spodoptera frugiperda (J.E. Smith) in Mexico. Reproduction of the braconid Chelonus insularis (Cresson), on treated egg masses was completely eliminated at 200 parts per million (ppm) and reduced by Â/70% at 20 ppm compared to the controls. Adult C. insularis did not avoid contact with residues on maize (200 ppm), but suffered a 7-day reduction in longevity after contact with residues. Initial toxicity of spinosad applied to a natural host of S. frugiperda was concentration dependent and resulted in 23 to 100% mortality of the eulophid Euplectrus plathypenae Howard at 25 to 200 ppm, respectively. The survival of Eu. plathypenae was initially reduced, especially in males, following contact with field weathered residues on maize (200 ppm). However, survival of both sexes rapidly returned to control values on foliage sampled after rainfall. A similar effect was observed in the mortality response of female Eu. plathypenae exposed to residues on sorghum. The ichneumonid Eiphosoma vitticolle Cresson did not avoid reproduction in S. frugiperda larvae that were externally contaminated with 200 ppm spinosad, although all spinosad-treated hosts died before the parasitoid progeny could develop. We use these results to predict the impact of spinosad applications on the foraging and reproduction of these parasitoids in the field. Such predictions require validation by field studies.
SUBLETHAL EFFECTS OF SPINOSAD (TRACER®) ON THE COTTON LEAFWORM (LEPIDOPTERA: NOCTUIDAE)
The effects of sublethal concentrations of spinosad (Tracer®) on development, fecundity, and food utilization, in the cotton leafworm, Spodoptera littoralis (Boisd.) were investigated. The fourth-instar larvae were fed on castor bean leaves treated with LC25 (13.9 ppm) or LC50 (57.8 ppm) of spinosad. Pupation and pupal weight were significantly reduced in both LC25 and LC50 treatments, compared with those of the controls. The fecundity rates of females in either LC25 or LC50 treatment were also reduced, compared with the controls. The residual activity of spinosad, applied on cotton at labeled field- and subfield-rates (200 and 70 g active substance (a.s.)/ 200 l water, respectively), was examined against the fifth-instar larvae of S. littoralis. Feeding deterrent effects were significantly demonstrated in larvae that fed on leaves collected from field plots with residual deposits of spinosad at 3 and 7 days old after application (DAA). The residual activity of spinosad on feeding and other metabolic parameters was decreased after 21 DAA indicating that the chemical started to degrade under field conditions. A histological study on midgut from larvae that previously fed on leaves treated with a concentration corresponding to the labeled-field rate of spinosad showed some alterations occurred after 48 and 96 h of treatment, compared to the normal midgut from the controls. The histological alterations included degeneration in the epithelial lining of the midgut and in the peritrophic matrix. Such histopathological effects are presumed to be responsible for the reduction in growth and food utilization caused by spinosad. It is, therefore, concluded that spinosad has sublethal effects on S. littoralis that may affect population dynamics in the field via reductions in survival and reproduction.
Journal of Economic Entomology, 2004
The toxicity of two biorational insecticides, spinosad (Tracer) and methoxyfenozide (RH-2485), was tested against eggs, larvae, and pupae of the noctuid Spodoptera littoralis (Boisduval). In the Þrst experiment, Þlter paper circles containing egg masses of two different age classes, young (Ͻ24 h old) and old (24 Ð 48 h old), were dipped in different concentrations of each insecticide diluted in either water or acetone. No ovicidal activity was recorded when insecticides were diluted in water. In contrast, when insecticides were diluted in acetone, both egg age classes generally showed a concentration-dependent response for both compounds. Mortality of larvae that hatched from both egg age classes was signiÞcantly increased, compared with control larvae, at all concentrations of both insecticides when diluted in water or acetone alike. The prevalence of mortality was similar with each insecticide. In the second experiment, third instars of S. littoralis were fed semisynthetic diet containing different concentrations of both insecticides. According to LC 50 values, no signiÞcant differences were observed between spinosad (2.11 mg [AI]/kg diet) and methoxyfenozide (3.98 mg [AI]/kg diet) after 48 h of treatment, based on the overlap of 95% CL. Toxic effects on the mortality of pupae, adult emergence, and the prevalence of deformed adults after topical application on young pupae also were examined. Only methoxyfenozide caused pupal mortality and deformed adults. Our results suggest that spinosad and methoxyfenozide are potentially potent compounds for control of S. littoralis.
Environmental Entomology, 2006
The toxicity of spinosad and methoxyfenozide against neonates and fourth instars of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) was tested under laboratory conditions. According to LC 50 values, no signiÞcant differences were observed between spinosad (0.50 mg [AI]/kg diet) and methoxyfenozide (0.54 mg [AI] /kg diet) after 48 h of ingestion treatment on neonate larvae, based on the overlap of 95% CL. Similarly, on fourth instars, no signiÞcant differences were observed between LC 50 (2.98 and 5.17 mg [AI]/kg diet for spinosad and methoxyfenozide, respectively, at 96 h after ingestion of artiÞcial diet) and LD 50 (4.74 and 2.68 g [AI]/g larva for spinosad and methoxyfenozide, respectively, at 144 h after topical application). In addition, spinosad and methoxyfenozide signiÞcantly suppressed weight gain of neonates and fourth instars continuously fed with artiÞcial diet containing the insecticides. The second part of this project was focused on the effects of methoxyfenozide on the reproduction of S. littoralis by determining the effect on oviposition in three different crosses and the pharmacokinetics pattern of ( 14 C)-methoxyfenozide in the body tissues of female and male adults after topical application in their excrement and in the deposited eggs to test transport through the female and the male adult. Methoxyfenozide negatively affected the reproduction of adults regardless the treated sex, presumably because of its presence in the adult body, accumulation in the laid eggs, and slow excretion of the product. We conclude that spinosad and methoxyfenozide represent an important choice to be used in integrated pest management where S. littoralis is a major pest.
Toxic Effects of Spinosad on Predatory Insects
Biological Control, 2002
Spinosad (Dow AgroSciences) is a mixture of tetracyclic-macrolide compounds produced by a soil actinomycete and has been classified as a bioinsecticide. Spinosad is highly active against Lepidoptera but is reported to be practically nontoxic to insect natural enemies. We assessed the impact of Spinosad in a granular maize-flour formulation on a selection of insect predators over periods of 2-14 days. In all cases, the quantities of Spinosad used were less than the maximum recommended rates given on the product label. Adults of Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae) suffered a high prevalence of mortality following consumption of 1000 or 2000 ppm Spinosad active ingredient (a.i.), but little mortality at 200 ppm. Larvae of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) did not consume the granular formulation and suffered little overall mortality. After 14 days of exposure, the earwig, Doru taeniatum (Dohrn) (Dermaptera:Forficulidae), suffered 48% mortality in the 1.2 ppm Spinosad treatment increasing to 98% in the 1200 ppm Spinosad treatment compared to 20% in controls. Earwigs suffered 86% mortality/intoxication 72 h after feeding on Spinosad-contaminated Spodoptera frugiperda J. E. Smith (Lepidoptera:Noctuidae) larvae. A field trial was performed to compare applications of commercial granular chlorpyrifos and Spinosad in maize-flour granules (200 and 2000 ppm a.i.; 4.8 -48 g a.i./ha, respectively) or as an aqueous spray (160 ppm a.i.; 48 g a.i./ha) on earwigs held inside gauze bags. Mortality of earwigs on control plants was less than 15% at 2 days postapplication compared to 33% on plants treated with granular chlorpyrifos, 83% on plants sprayed with 160 ppm Spinosad, and 91-95% on plants treated with 200 -2000 ppm Spinosad granules, respectively. Further mortality in the 24-h period postsampling ranged from <5% in control treatments, to 9% in the chlorpyrifos treatment, and to 55-65% in the Spinosad spray and granule treatments. We conclude that Spinosad cannot be considered to have an environmental safety profile similar to most established biological insecticides. © 2002 Elsevier Science
Mature third-instar larvae of the parasitoid Hyposoter didymator (Thunberg) should be considered as a susceptible stage because as demonstrated in this study, when they exit frOID the dead host to spin the silken cocoon, they are very exposed to pesticides due to their low mability and absence of concealment inside the host. The rOBC classification for standard tests (residual exposure) was also used in the other exposure routes, to classify insecticides according to the total effect caused in the enemy. Topically applied at the maximum fieId recommended concentrations in Spain, the insect growth regulatars (IGRs) tebufenozide (TEB) and methoxyfenozide (MET), were not toxic to tbis developmental stage (rOBC class 1). The IGRs diflubenzuron (DFB), pyriproxyfen (PYR) llild azadirachtin (AZA) and the l1aturalyte spinosad (SPIN) were slightly, moderately or verj harmful, and they were classified as rOBe classes 2 CAZA), 3 (PYR) and 4 (DFB and SPIN). In contrast with results reponed for other natural enemies, pupae were rather susceptible when treated with 1¡..tI of 11.2A and DFB (IOBC class 2) ar PYR and SPIN (IOBC class 4). Only TEB and MET were harrnless (IOBC class 1). Adults of the parasitoíd were more tolerant to the studied IGRs which were classified as IOBC class 1 in residual or topical tests, and IOBC classes 1 and 2 in ingestion assays. Fresh resid{1es of SPIN however, were very toxic to the wasp adults (IOBC class 4) but they had little residual toxicity at 10 days post application (IOBC c1ass 1). In topical ar ingestion assays, the toxicity of SPIN was very high to adults (rOBe c1asses 4). The ÍI1L11lature stages (concealed inside me host) were not affected by A2A, DFB, MET, TEB and SPIN topically applied to parasitized LJ larvae of the host and all 01' them were classified as rOBe class 1..
2004
Mature third-instar larvae of the parasitoid Hyposoter didymator (Thunberg) should be considered as a susceptible stage because as demonstrated in this study, when they exit frOID the dead host to spin the silken cocoon, they are very exposed to pesticides due to their low mability and absence of concealment inside the host. The rOBC classification for standard tests (residual exposure) was also used in the other exposure routes, to classify insecticides according to the total effect caused in the enemy. Topically applied at the maximum fieId recommended concentrations in Spain, the insect growth regulatars (IGRs) tebufenozide (TEB) and methoxyfenozide (MET), were not toxic to tbis developmental stage (rOBC class 1). The IGRs diflubenzuron (DFB), pyriproxyfen (PYR) llild azadirachtin (AZA) and the l1aturalyte spinosad (SPIN) were slightly, moderately or verj harmful, and they were classified as rOBe classes 2 CAZA), 3 (PYR) and 4 (DFB and SPIN). In contrast with results reponed for other natural enemies, pupae were rather susceptible when treated with 1¡..tI of 11.2A and DFB (IOBC class 2) ar PYR and SPIN (IOBC class 4). Only TEB and MET were harrnless (IOBC class 1). Adults of the parasitoíd were more tolerant to the studied IGRs which were classified as IOBC class 1 in residual or topical tests, and IOBC classes 1 and 2 in ingestion assays. Fresh resid{1es of SPIN however, were very toxic to the wasp adults (IOBC class 4) but they had little residual toxicity at 10 days post application (IOBC c1ass 1). In topical ar ingestion assays, the toxicity of SPIN was very high to adults (rOBe c1asses 4). The ÍI1L11lature stages (concealed inside me host) were not affected by A2A, DFB, MET, TEB and SPIN topically applied to parasitized LJ larvae of the host and all 01' them were classified as rOBe class 1..
The maximum fieid recoITh"'TIcndedeoneentratiens (based en the reeommended maximum [ield rate and a water amount of 1000 liha) ef spinesad (120 mg a.i./l) and the IGRs tebufenozide(144 mg a.i./i), methoxyfenozide (J44 mg a.i./l), diflubenzuron (100 mg a.i./l), azadiraehtin (48 mg a.i.l1) and pyriproxyfen (75 mg a.i./I) were tested in the laboratory on adults of the parasitoid Hyposoter didymmor using different bioassays. Fresh residues of spinosad on glass surfaees were highly toxic to the natural enemy, eausing 100% mortality of adults. However, the de1eterious effeet of the insecticide deereased quickly with the age of the residues, and lO-d-old residues did not cause any mortality or modified longevity. Fresh residues and five-d-old residues ofazadirachtin reduced the benefieial cilpacity of females. In the sarne assay, tebufenozide, methoxifenozide, diflubenzuron and pyriproxyfen were nontoxie irrespeetive of the age of the residue: Spinosad topically applied eaused mortalitíes >95% and azadirachtin deereased the number of attacked hosts per female. The ather insectieides did not affeet any life parameter of the parasitoid. The IGRs tested had a mínimal oral toxicity to adults of H didymator after 72 h, but spinosad caused more than 80% mortality. Longevity was decreased by spinosad and azadiraehtin, and the benefieial capacity lowered by any inseetieide but tebufenozide and methoxyfenozide.