Effects of Two Biorational Insecticides, Spinosad and Methoxyfenozide, on Spodoptera littoralis (Lepidoptera: Noctuidae) Under Laboratory Conditions (original) (raw)
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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.
Journal of Economic Entomology, 2007
Susceptibility to methoxyfenozide of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) larvae was determined through exposure of neonate and fourth instars to dipped and sprayed pepper, Capsicum annum L., leaves. Methoxyfenozide and spinosad were tested against adults of this noctuid by oral, residual, and topical application. In larvae, we evaluated Þve (range, 0.001Ð10 mg active ingredient [AI]/liter) and six (range, 1Ð250 mg [AI]/liter) concentration levels by instars, respectively, by using two application methods at three different age leaf residues (0, 3, and 6 d after application). According to LC 50 values, no signiÞcant differences were observed between the same age leaf residues of both application methods at 96 and 72 h after ingestion treatment on neonates and fourth instars, respectively. Nevertheless, toxicity of methoxyfenozide decreased signiÞcantly after time. For both application methods, the LC 50 values of the Þrst leaf residue (0 d after application) were signiÞcantly lower than those of 6-d-old residues. Furthermore, larval weight of fourth instars fed for 48 h with pepper, Capsicum annum L., leaves containing methoxyfenozide was signiÞcantly suppressed. Spinosad and methoxyfenozide reduced in a dose-dependent manner the fecundity and fertility of S. littoralis adults when treated oral and residually. Likewise, when methoxyfenozide was administered orally in three different adult crosses, the fecundity was strongly affected, independently of the treated sex. We conclude that the combination of lethal and sublethal effects of methoxyfenozide and spinosad might exhibit signiÞcant effects on the population dynamics of S. littolaris.
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.
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.
Susceptibility to methoxyfenozide of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) larvae was determined through exposure of neonate and fourth instars to dipped and sprayed pepper, Capsicum annum L., leaves. Methoxyfenozide and spinosad were tested against adults of this noctuid by oral, residual, and topical application. In larvae, we evaluated Þve (range, 0.001Ð10 mg active ingredient [AI]/liter) and six (range, 1Ð250 mg [AI]/liter) concentration levels by instars, respectively, by using two application methods at three different age leaf residues (0, 3, and 6 d after application). According to LC 50 values, no signiÞcant differences were observed between the same age leaf residues of both application methods at 96 and 72 h after ingestion treatment on neonates and fourth instars, respectively. Nevertheless, toxicity of methoxyfenozide decreased signiÞcantly after time. For both application methods, the LC 50 values of the Þrst leaf residue (0 d after application) were signiÞcantly lower than those of 6-d-old residues. Furthermore, larval weight of fourth instars fed for 48 h with pepper, Capsicum annum L., leaves containing methoxyfenozide was signiÞcantly suppressed. Spinosad and methoxyfenozide reduced in a dose-dependent manner the fecundity and fertility of S. littoralis adults when treated oral and residually. Likewise, when methoxyfenozide was administered orally in three different adult crosses, the fecundity was strongly affected, independently of the treated sex. We conclude that the combination of lethal and sublethal effects of methoxyfenozide and spinosad might exhibit signiÞcant effects on the population dynamics of S. littolaris.
The lethal and sublethal effects of the ecdysone agonist methoxyfenozide on the fall armyworm, Spodoptera frugiperda (J. E. Smith), were investigated by feeding a methoxyfenozide-treated diet to ifth instars until pupation in doses corresponding to the LC 10 and LC 25 for the compound. Larval mortality reached 8% and 26% in the low and high concentration groups, respectively, on the seventh day of the experiment. A progressive larval mortality of 12% for the LC 10 and 60% for the LC 25 was observed before pupation. Treated larvae exhibited lower pupal weights, higher pupal mortality, presence of deformed pupae, and more deformed adults than untreated larvae. The incorporation of methoxyfenozide into the diet had a signi icant effect on the timing of larval development. The development period for males and females was about seven days longer than the controls for both concentrations tested. In contrast, the compound affected neither pupae nor adult longevity. Finally, S. frugiperda adults that resulted from ifth instars treated with methoxyfenozide were not affected in their mean cumulative number of eggs laid per female (fecundity), nor percentages of eggs hatched (fertility), or the sex ratio. Our results suggest that the combination of lethal and sublethal effects of methoxyfenozide may have important implications for the population dynamics of the fall armyworm.
Toxicity and Sublethal Effects of Methoxyfenozide on Spodoptera exigua (Lepidoptera: Noctuidae)
Journal of Economic Entomology, 2010
The toxicity and sublethal effects of methoxyfenozide were evaluated in third instars of the beet armyworm, Spodoptera exigua (Hü bner) (Lepidoptera: Noctuidae), that fed on contaminated semisynthetic diet. The LC 50 value was estimated at 0.23 mg of active ingredient (AI)/kg diet (range, 95% CI: 0.17Ð 0.37) at 264 h after treatment. The effects on development, survival, and reproduction were observed in third instars of this pest that survived exposure to an LC 25 concentration of methoxyfenozide. The larvae from the insecticide treatment exhibited lower pupal weights, an increase in both larval and pupal developmental times and a higher frequency of malformations of the wings in adults than untreated larvae. Adults from the methoxyfenozide treatment did not show reduced fecundity (mean cumulative number of eggs laid per female), but fertility as measured by the percentage of eggs hatched (fertility) was signiÞcantly reduced compared with untreated control insects. No signiÞcant effects were observed on pupal sex ratio. We concluded that the lethal and sublethal effects of methoxyfenozide are likely to have a signiÞcant impact on S. exigua populations on treated crops.
BioControl, 2008
The toxicity of spinosad was evaluated using the RaPID Assay 1 Spinosad immunosorbent assay in different developmental stages of the parasitoid, Hyposoter didymator, and in its host, fourth-instar larvae of the cotton leafworm Spodoptera littoralis. Spinosad was applied directly to pupae and adults of H. didymator (ingestion or topical application) or to the immature stages of the parasitoid via the host larvae. Low amounts of spinosad were recovered from S. littoralis host larvae after topical treatment, and the compound was mainly retained in the hemolymph. Amounts of spinosad detected in thirdinstar larvae of H. didymator, pulled out from the hemolymph of parasitized S. littoralis larvae, were 85 pg (3.57 ng a.i./g body weight) in dead larvae, and 82 pg (3.42 ng a.i./g body weight) in alive individuals. After topical treatment of H. didymator cocoons, most of the compound was retained in the silken cocoon, preventing contamination of the pupa. Also in the parasitoid adults, relatively low amounts of spinosad were accumulated in the body overall, but half of all the insecticide recovered was found in the ovaries. The kinetic results obtained help to better understand the toxicity of spinosad in the complex S. littoralis-H. didymator, and to ascertain the compatibility between spinosad and the parasitoid for optimizing the control of lepidopteran pests.
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.