JUAN CISNEROS | Pontificia Universidad Javeriana (original) (raw)
Papers by JUAN CISNEROS
Biological Control, 2002
The efficacy of bioinsecticides that act by ingestion can be improved by the use of phagostimulan... more The efficacy of bioinsecticides that act by ingestion can be improved by the use of phagostimulant formulations that increase the consumption of the pathogen. A granule recipe comprising of pregelatinized flour, starch, ground maize cob, maize oil, and water was identified that was highly palatable to Spodoptera frugiperda larvae. To compare the performance of a multiple nucleopolyhedrovirus (SfMNPV) in aqueous spray and phagostimulant granules, multiple linear regression procedures were employed to analyze the results of seven independent field trials involving spray applications and eight independent field trials involving application of phagostimulant granules for control of S. frugiperda in maize. Prevalence of infection was positively correlated with the quantity of inoculum applied but negatively correlated with the interval between application and sampling of larvae for both granular and spray formulations. Virus-induced mortality was greater when inoculum was applied in granular than in spray formulation. A field experiment involving the application of 1:5 Â 10 12 occlusion bodies (OBs)/ha in quantities of 6, 18, and 32 kg granules/ha indicated that the quantity of granules applied did not significantly affect viral mortality at any timepoint. Persistence of activity of viral inoculum applied in spray or granular formulations was significantly greater when applied in the granular formulation, with approximately 23% of the original activity remaining at 8 days postapplication compared to <1% in the spray-treated plants. We conclude that the efficacy of SfMNPV was improved by formulation; the granular formulation caused a higher prevalence of infection in S. frugiperda larvae and persisted longer on crop foliage compared to an aqueous spray application. The cost of the formulation ingredients alone was approximately US$0.50/kg. When combined with the virus, the cost of the basic bioinsecticide components would be about US$17/ha, although this estimate does not include additional costs involved in the commercialization of a potential bioinsecticide product. Ó
Behavioral Ecology and Sociobiology, 2000
The incidence of cannibalism of larval Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize un... more The incidence of cannibalism of larval Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize under field conditions was investigated using field cages. Cannibalism was found to account for approximately 40% mortality when maize plants were infested with two or four fourth-instar larvae over a 3-day period. Field trials examined the effect of larval density on the prevalence of natural enemies of S. frugiperda. The abundance of predators (earwigs, staphylinids, other predatory beetles, and Chrysoperla spp.) was significantly greater on maize plants with higher levels of larval feeding damage, while the relationship between predator abundance and number of S. frugiperda larvae per plant was less clear. As larval damage is probably a more reliable indicator of previous larval density than numbers collected at an evaluation, this indicates that predation risk will be greater for larvae living in large groups. Parasitism accounted for 7.1% mortality of larvae in sorghum, and involved six species of Hymenoptera and Tachinidae. There was no effect of larval density or within-plant distribution on the probability of larval attack by parasito-ids. The selective benefits of cannibalism, in relation to the risk of predation and parasitism, are discussed.
Biological Control, 2002
Spinosad (Dow AgroSciences) is a neurotoxin mixture produced during fermentation of a soil actino... more Spinosad (Dow AgroSciences) is a neurotoxin mixture produced during fermentation of a soil actinomycete that has high activity towards Lepidoptera. Diet surface contamination bioassays were performed with Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) and Spinosad alone and in mixtures. The interaction of SfMPNV + Spinosad mixtures in S. frugiperda larvae was generally independent or slightly antagonistic in nature, although weak synergism was detected in mixtures containing 3 ppm Spinosad + 20 or 70 occlusion bodies/mm 2 diet of SfMNPV. Mean time to death was not a reliable indicator of mortality over time in larvae exposed to SfMNPV-Spinosad mixtures because Spinosad killed larvae quickly whereas virus mortality occurred at a much lower rate. Therefore, threshold tolerance analysis was employed to generate time-response curves that showed two clear phases; an initial response to Spinosad until $100 h followed by virus-induced mortality at 120-250 h post-contamination. A field trial was performed to assess the degree of pest control achieved by SfMNPV-Spinosad mixtures applied to maize. Recovery of S. frugiperda larvae was significantly reduced in all treatments compared to recovery from control plots. The mixture of SfMNPV with 3 ppm Spinosad resulted in ca. 90% S. frugiperda control, which was 12.5-32% greater than for plots treated with SfMNPV alone. The impact of low concentrations of Spinosad on non-target arthropods present in the maize crop was evaluated in a field trial. Application of 3 ppm Spinosad had very little effect on the abundance of insect natural enemies present on maize plants, whereas application of the product label recommended rate of 200 ppm Spinosad had effects similar to those observed following application of chlorpyrifos. The use of low concentrations of Spinosad merits further study as a means of controlling lepidopteran pests either alone or in combination with other entomopathogens. Ó
Biological Control, 2002
The degree of control of the fall armyworm, Spodoptera frugiperda, by a multiple nucleopolyhedrov... more The degree of control of the fall armyworm, Spodoptera frugiperda, by a multiple nucleopolyhedrovirus (SfMNPV) appears to be limited by the quantity of inoculum consumed by the insect and the delivery of the virus to the insect feeding site. The formulation of the virus with phagostimulants and/or viral synergists, such as boric acid, may help overcome this problem. The present study aimed to determine the degree of potentiation of boric acid toward SfM-NPV in a granular phagostimulant formulation. In a laboratory bioassay the LC 50 value for second-instar larvae was reduced from 114 virus occlusion bodies (OBs)/mm 2 of diet surface for virus alone to 51 OBs/ mm 2 of diet in the presence of 1% boric acid. The mean time to death of larvae exposed to virus mixed with 0.5 or 1% boric acid was not significantly different from that of larvae inoculated with virus alone. Increasing the concentration of boric acid at a single determined concentration of virus (80 OBs/mm 2 ) resulted in a significant increase in the prevalence of virus-induced mortality. The boric acid alone did not cause S. frugiperda mortality at the concentrations tested. A field trial performed with S. frugiperda larvae held on plants within fine gauze bags indicated that application of maize flour granules containing virus ؉ 1% boric acid caused a significant increase in virus-induced mortality compared to application of granules containing virus alone. A randomized block experiment performed later also resulted in a higher prevalence of virus-induced mortality in S. frugiperda larvae exposed to virus mixed with 1% boric acid in samples collected at 5 days postapplication and reared in the laboratory until death or pupation, but not in samples made at 1 day and 3 days postapplication. Differences in the prevalence of virus infection in insects collected at each time point may have been related to the consistency of the granular formulation, which turned into a paste and adhered to the surface of maize plants under conditions of heavy rainfall. Granules containing 1 and 4% boric acid were not toxic to the earwig, Doru taeniatum, in the laboratory. The same concentrations of boric acid sprayed onto maize plants did not significantly reduce the abundance of natural enemies or other nontarget insects at any sample time point. Boric acid offers an economical means of enhancing baculovirus activity with little apparent risk to nontarget arthropods. © 2002 Elsevier Science
Biocontrol Science and Technology, 2005
Laboratory studies were performed on the lethal and sublethal effects of spinosad on three import... more 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.
Journal of Economic Entomology, 2003
The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), ... more The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), and pyrethroid (cypermethrin) insecticides on insect natural enemies was compared with that of a nucleopolyhedrovirus (Baculoviridae) of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in maize grown in southern Mexico. Analyses of the SELECTV and Koppert Side Effects (IOBC) databases on the impact of synthetic insecticides on arthropod natural enemies were used to predict Ϸ75Ð90% natural enemy mortality after application, whereas the bioinsecticide was predicted to have no effect. Three Þeld trails were performed in mid-and late-whorl stage maize planted during the growing season in Chiapas State, Mexico. Synthetic insecticides were applied at product label recommended rates using a manual knapsack sprayer Þtted with a cone nozzle. The biological pesticide was applied at a rate of 3 ϫ 10 12 occlusion bodies (OBs)/ha using identical equipment. Pesticide impacts on arthropods on maize plants were quantiÞed at intervals between 1 and 22 d postapplication. The biological insecticide based on S. frugiperda nucleopolyhedrovirus had no adverse effect on insect natural enemies or other nontarget insect populations. Applications of the carbamate, pyrethroid, and organophosphate insecticides all resulted in reduced abundance of insect natural enemies, but for a relatively short period (8 Ð15 d). Pesticide applications made to late-whorl stage maize resulted in lesser reductions in natural enemy populations than applications made at the mid-whorl stage, probably because of a greater abundance of physical refuges and reduced spray penetration of late-whorl maize.
Biological Control, 1999
Near identical trials conducted concurrently in maize plots in Honduras and Mexico produced simil... more Near identical trials conducted concurrently in maize plots in Honduras and Mexico produced similar results in the pattern of larval mortality of Spodoptera frugiperda following application of a baculovirus or a conventional synthetic insecticide. The highest application rates of virus resulted in approximately 40% mortality of S. frugiperda larvae. Virus-induced mortality decreased with time. Parasitism by wasps and tachinids also contributed up to 40% mortality in field-collected larvae. The application of chlorpyrifos resulted in a resurgence of S. frugiperda. Chlorpyrifos also reduced a number of important predators in the maize crop which is likely to have been influential in the observed resurgence of this pest. The use of granulated sugar in the viral formulation caused an increase in the population density of several maize-associated insect species, and in Mexico a transient increase in parasitism was observed in sugar-treated plots. Sugar did not appear to increase the probability of infection by acting as a feeding stimulant in either trial. A preliminary analysis of the cost of viral production and application indicates that virus was considerably more costly than conventional control. To be commercially viable, economies of scale both in the cost of raw material for the insect diet and in the efficiency of manpower-related activities are needed to substantially reduce the costs of the viral product. Despite high levels of infestation by S. frugiperda, grain weight/ cob was not significantly improved by the application of the biological or synthetic insecticide. Natural mortality factors both biotic and abiotic appear to have a large impact on larval S. frugiperda populations. For improvements in yield, the impact of control measures against S. frugiperda may be dependent on plant growth stage. Trials on timing and frequency of virus application are in progress to test this idea. 1999 Academic Press
International Journal of Pest Management, 2003
A pilot study performed on the Pacific coastal plain of Chiapas, Mexico, focused on the prevalenc... more A pilot study performed on the Pacific coastal plain of Chiapas, Mexico, focused on the prevalence of maize crop infestation by insect pests, parasitism of pests and the abundance of insect predators in maize plots with weeds compared with plots under a regime of rigorous manual weed control. Sampling was conducted on four occasions at 20, 32, 44 and 56 days post-planting. Infestation of maize by fall armyworm larvae, Spodoptera frugiperda (Lepidoptera: Noctuidae), was more than twice as great in plots with strict weed control compared with weedy plots at 20 days post-planting, but declined thereafter in both treatments. The prevalence of aphid infestation and the abundance of nitidulid beetles were consistently greater in weedcontrolled plots. In contrast, the density of beneficial predatory Coleoptera increased significantly in plots with weeds, and it is suggested that this probably explains the lower incidence of pests. S. frugiperda egg masses placed in experimental plots suffered a significantly higher incidence rate of parasitism by Chelonus insularis (Hymenoptera: Braconidae) in clean plots (42.0%) compared with those placed in weedy plots (3.75%); it is suspected that weeds may hinder the location of egg masses by parasitoids. Overall, the presence or absence of weeds had a marked influence on the arthropod community present in maize fields. The weeds did not affect maize plant height, the levels of plant damage or the yield of grain from plants under each type of weed regime, implying that competitive effects of weeds may be offset by greater numbers of beneficial insects in weedy plots. Our pilot study indicates that strict weed control in maize may be unnecessary.
Entomologia Experimentalis Et Applicata, 2001
The behaviour of two abundant predators in Mesoamerican maize crops, Chrysoperla rufilabris larva... more The behaviour of two abundant predators in Mesoamerican maize crops, Chrysoperla rufilabris larvae and Doru taeniatum adults, towards healthy and nucleopolyhedrovirus-infected Spodoptera frugiperda larvae was compared. C. rufilabris did not discriminate between healthy and virus-infected prey, although the mean search time was approximately two times longer towards virus-infected larvae. In contrast, D. taeniatum directed a greater proportion of their attacks towards virus-infected prey but there was no significant difference in the search time. Prey consumption time did not differ significantly for each type of prey by either predator, although prey consumption was much faster in D. taeniatum. Viable virus was detected in D. taeniatum faeces up to 3 d after feeding on infected S. frugiperda larvae, whereas virus was inactivated in the gut of C. rufilabris. Both predators were shown to have acidic guts. A field experiment demonstrated that D. taeniatum that had fed on infected prey could contaminate foliage resulting in the transmission of the disease at a low prevalence (4.7%) to S. frugiperda larvae in a field maize crop.
Journal of Economic Entomology, 2004
were performed to determine the efÞcacy of maize ßour-based granular formulations with ultralow r... more were performed to determine the efÞcacy of maize ßour-based granular formulations with ultralow rates of the naturally derived insecticide spinosad (0.1, 0.3, and 1.0 g [AI]/ha), for control of Spodoptera frugiperda (J.E. Smith) in maize, Zea mays L., in southern Mexico. Spinosad formulations were compared with a chemical standard, a commercial granular formulation of chlorpyrifos (150 g [AI]/ha). In both years, application of spinosad resulted in excellent levels of control, indicated by the number of living S. frugiperda larvae recovered from experimental plots. The efÞcacy of spinosad applied at 0.3 and 1.0 g (AI)/ha was very similar to that of chlorpyrifos. Natural reinfestation caused S. frugiperda numbers in insecticide treated plots to return to values similar to the control treatment by 10 Ð15 d postapplication. Many spinosad-intoxicated larvae collected in the Þeld died later in the laboratory in 2002, but not in 2003. Percentage mortality due to parasitoid emergence did not differ in any treatment in either Þeld trial. The number of parasitoids that emerged from S. frugiperda collected in each treatment was signiÞcantly reduced after application of spinosad (all rates) or chlorpyrifos due to a reduction in the number of host larvae. Parasitoid numbers returned to control values by 9 Ð15 d postapplication in all treatments. The most prevalent parasitoid was the braconid Chelonus insularis Cresson, which represented Ϸ80% of emerging parasitoids in both years. We conclude that appropriate formulation technology can greatly enhance the performance of this naturally derived, biorational insecticide.
Biological Control, 2002
The efficacy of bioinsecticides that act by ingestion can be improved by the use of phagostimulan... more The efficacy of bioinsecticides that act by ingestion can be improved by the use of phagostimulant formulations that increase the consumption of the pathogen. A granule recipe comprising of pregelatinized flour, starch, ground maize cob, maize oil, and water was identified that was highly palatable to Spodoptera frugiperda larvae. To compare the performance of a multiple nucleopolyhedrovirus (SfMNPV) in aqueous spray and phagostimulant granules, multiple linear regression procedures were employed to analyze the results of seven independent field trials involving spray applications and eight independent field trials involving application of phagostimulant granules for control of S. frugiperda in maize. Prevalence of infection was positively correlated with the quantity of inoculum applied but negatively correlated with the interval between application and sampling of larvae for both granular and spray formulations. Virus-induced mortality was greater when inoculum was applied in granular than in spray formulation. A field experiment involving the application of 1:5 Â 10 12 occlusion bodies (OBs)/ha in quantities of 6, 18, and 32 kg granules/ha indicated that the quantity of granules applied did not significantly affect viral mortality at any timepoint. Persistence of activity of viral inoculum applied in spray or granular formulations was significantly greater when applied in the granular formulation, with approximately 23% of the original activity remaining at 8 days postapplication compared to <1% in the spray-treated plants. We conclude that the efficacy of SfMNPV was improved by formulation; the granular formulation caused a higher prevalence of infection in S. frugiperda larvae and persisted longer on crop foliage compared to an aqueous spray application. The cost of the formulation ingredients alone was approximately US$0.50/kg. When combined with the virus, the cost of the basic bioinsecticide components would be about US$17/ha, although this estimate does not include additional costs involved in the commercialization of a potential bioinsecticide product. Ó
Behavioral Ecology and Sociobiology, 2000
The incidence of cannibalism of larval Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize un... more The incidence of cannibalism of larval Spodoptera frugiperda (Lepidoptera: Noctuidae) on maize under field conditions was investigated using field cages. Cannibalism was found to account for approximately 40% mortality when maize plants were infested with two or four fourth-instar larvae over a 3-day period. Field trials examined the effect of larval density on the prevalence of natural enemies of S. frugiperda. The abundance of predators (earwigs, staphylinids, other predatory beetles, and Chrysoperla spp.) was significantly greater on maize plants with higher levels of larval feeding damage, while the relationship between predator abundance and number of S. frugiperda larvae per plant was less clear. As larval damage is probably a more reliable indicator of previous larval density than numbers collected at an evaluation, this indicates that predation risk will be greater for larvae living in large groups. Parasitism accounted for 7.1% mortality of larvae in sorghum, and involved six species of Hymenoptera and Tachinidae. There was no effect of larval density or within-plant distribution on the probability of larval attack by parasito-ids. The selective benefits of cannibalism, in relation to the risk of predation and parasitism, are discussed.
Biological Control, 2002
Spinosad (Dow AgroSciences) is a neurotoxin mixture produced during fermentation of a soil actino... more Spinosad (Dow AgroSciences) is a neurotoxin mixture produced during fermentation of a soil actinomycete that has high activity towards Lepidoptera. Diet surface contamination bioassays were performed with Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) and Spinosad alone and in mixtures. The interaction of SfMPNV + Spinosad mixtures in S. frugiperda larvae was generally independent or slightly antagonistic in nature, although weak synergism was detected in mixtures containing 3 ppm Spinosad + 20 or 70 occlusion bodies/mm 2 diet of SfMNPV. Mean time to death was not a reliable indicator of mortality over time in larvae exposed to SfMNPV-Spinosad mixtures because Spinosad killed larvae quickly whereas virus mortality occurred at a much lower rate. Therefore, threshold tolerance analysis was employed to generate time-response curves that showed two clear phases; an initial response to Spinosad until $100 h followed by virus-induced mortality at 120-250 h post-contamination. A field trial was performed to assess the degree of pest control achieved by SfMNPV-Spinosad mixtures applied to maize. Recovery of S. frugiperda larvae was significantly reduced in all treatments compared to recovery from control plots. The mixture of SfMNPV with 3 ppm Spinosad resulted in ca. 90% S. frugiperda control, which was 12.5-32% greater than for plots treated with SfMNPV alone. The impact of low concentrations of Spinosad on non-target arthropods present in the maize crop was evaluated in a field trial. Application of 3 ppm Spinosad had very little effect on the abundance of insect natural enemies present on maize plants, whereas application of the product label recommended rate of 200 ppm Spinosad had effects similar to those observed following application of chlorpyrifos. The use of low concentrations of Spinosad merits further study as a means of controlling lepidopteran pests either alone or in combination with other entomopathogens. Ó
Biological Control, 2002
The degree of control of the fall armyworm, Spodoptera frugiperda, by a multiple nucleopolyhedrov... more The degree of control of the fall armyworm, Spodoptera frugiperda, by a multiple nucleopolyhedrovirus (SfMNPV) appears to be limited by the quantity of inoculum consumed by the insect and the delivery of the virus to the insect feeding site. The formulation of the virus with phagostimulants and/or viral synergists, such as boric acid, may help overcome this problem. The present study aimed to determine the degree of potentiation of boric acid toward SfM-NPV in a granular phagostimulant formulation. In a laboratory bioassay the LC 50 value for second-instar larvae was reduced from 114 virus occlusion bodies (OBs)/mm 2 of diet surface for virus alone to 51 OBs/ mm 2 of diet in the presence of 1% boric acid. The mean time to death of larvae exposed to virus mixed with 0.5 or 1% boric acid was not significantly different from that of larvae inoculated with virus alone. Increasing the concentration of boric acid at a single determined concentration of virus (80 OBs/mm 2 ) resulted in a significant increase in the prevalence of virus-induced mortality. The boric acid alone did not cause S. frugiperda mortality at the concentrations tested. A field trial performed with S. frugiperda larvae held on plants within fine gauze bags indicated that application of maize flour granules containing virus ؉ 1% boric acid caused a significant increase in virus-induced mortality compared to application of granules containing virus alone. A randomized block experiment performed later also resulted in a higher prevalence of virus-induced mortality in S. frugiperda larvae exposed to virus mixed with 1% boric acid in samples collected at 5 days postapplication and reared in the laboratory until death or pupation, but not in samples made at 1 day and 3 days postapplication. Differences in the prevalence of virus infection in insects collected at each time point may have been related to the consistency of the granular formulation, which turned into a paste and adhered to the surface of maize plants under conditions of heavy rainfall. Granules containing 1 and 4% boric acid were not toxic to the earwig, Doru taeniatum, in the laboratory. The same concentrations of boric acid sprayed onto maize plants did not significantly reduce the abundance of natural enemies or other nontarget insects at any sample time point. Boric acid offers an economical means of enhancing baculovirus activity with little apparent risk to nontarget arthropods. © 2002 Elsevier Science
Biocontrol Science and Technology, 2005
Laboratory studies were performed on the lethal and sublethal effects of spinosad on three import... more 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.
Journal of Economic Entomology, 2003
The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), ... more The impact of commonly used organophosphate (chlorpyrifos, methamidophos), carbamate (carbaryl), and pyrethroid (cypermethrin) insecticides on insect natural enemies was compared with that of a nucleopolyhedrovirus (Baculoviridae) of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in maize grown in southern Mexico. Analyses of the SELECTV and Koppert Side Effects (IOBC) databases on the impact of synthetic insecticides on arthropod natural enemies were used to predict Ϸ75Ð90% natural enemy mortality after application, whereas the bioinsecticide was predicted to have no effect. Three Þeld trails were performed in mid-and late-whorl stage maize planted during the growing season in Chiapas State, Mexico. Synthetic insecticides were applied at product label recommended rates using a manual knapsack sprayer Þtted with a cone nozzle. The biological pesticide was applied at a rate of 3 ϫ 10 12 occlusion bodies (OBs)/ha using identical equipment. Pesticide impacts on arthropods on maize plants were quantiÞed at intervals between 1 and 22 d postapplication. The biological insecticide based on S. frugiperda nucleopolyhedrovirus had no adverse effect on insect natural enemies or other nontarget insect populations. Applications of the carbamate, pyrethroid, and organophosphate insecticides all resulted in reduced abundance of insect natural enemies, but for a relatively short period (8 Ð15 d). Pesticide applications made to late-whorl stage maize resulted in lesser reductions in natural enemy populations than applications made at the mid-whorl stage, probably because of a greater abundance of physical refuges and reduced spray penetration of late-whorl maize.
Biological Control, 1999
Near identical trials conducted concurrently in maize plots in Honduras and Mexico produced simil... more Near identical trials conducted concurrently in maize plots in Honduras and Mexico produced similar results in the pattern of larval mortality of Spodoptera frugiperda following application of a baculovirus or a conventional synthetic insecticide. The highest application rates of virus resulted in approximately 40% mortality of S. frugiperda larvae. Virus-induced mortality decreased with time. Parasitism by wasps and tachinids also contributed up to 40% mortality in field-collected larvae. The application of chlorpyrifos resulted in a resurgence of S. frugiperda. Chlorpyrifos also reduced a number of important predators in the maize crop which is likely to have been influential in the observed resurgence of this pest. The use of granulated sugar in the viral formulation caused an increase in the population density of several maize-associated insect species, and in Mexico a transient increase in parasitism was observed in sugar-treated plots. Sugar did not appear to increase the probability of infection by acting as a feeding stimulant in either trial. A preliminary analysis of the cost of viral production and application indicates that virus was considerably more costly than conventional control. To be commercially viable, economies of scale both in the cost of raw material for the insect diet and in the efficiency of manpower-related activities are needed to substantially reduce the costs of the viral product. Despite high levels of infestation by S. frugiperda, grain weight/ cob was not significantly improved by the application of the biological or synthetic insecticide. Natural mortality factors both biotic and abiotic appear to have a large impact on larval S. frugiperda populations. For improvements in yield, the impact of control measures against S. frugiperda may be dependent on plant growth stage. Trials on timing and frequency of virus application are in progress to test this idea. 1999 Academic Press
International Journal of Pest Management, 2003
A pilot study performed on the Pacific coastal plain of Chiapas, Mexico, focused on the prevalenc... more A pilot study performed on the Pacific coastal plain of Chiapas, Mexico, focused on the prevalence of maize crop infestation by insect pests, parasitism of pests and the abundance of insect predators in maize plots with weeds compared with plots under a regime of rigorous manual weed control. Sampling was conducted on four occasions at 20, 32, 44 and 56 days post-planting. Infestation of maize by fall armyworm larvae, Spodoptera frugiperda (Lepidoptera: Noctuidae), was more than twice as great in plots with strict weed control compared with weedy plots at 20 days post-planting, but declined thereafter in both treatments. The prevalence of aphid infestation and the abundance of nitidulid beetles were consistently greater in weedcontrolled plots. In contrast, the density of beneficial predatory Coleoptera increased significantly in plots with weeds, and it is suggested that this probably explains the lower incidence of pests. S. frugiperda egg masses placed in experimental plots suffered a significantly higher incidence rate of parasitism by Chelonus insularis (Hymenoptera: Braconidae) in clean plots (42.0%) compared with those placed in weedy plots (3.75%); it is suspected that weeds may hinder the location of egg masses by parasitoids. Overall, the presence or absence of weeds had a marked influence on the arthropod community present in maize fields. The weeds did not affect maize plant height, the levels of plant damage or the yield of grain from plants under each type of weed regime, implying that competitive effects of weeds may be offset by greater numbers of beneficial insects in weedy plots. Our pilot study indicates that strict weed control in maize may be unnecessary.
Entomologia Experimentalis Et Applicata, 2001
The behaviour of two abundant predators in Mesoamerican maize crops, Chrysoperla rufilabris larva... more The behaviour of two abundant predators in Mesoamerican maize crops, Chrysoperla rufilabris larvae and Doru taeniatum adults, towards healthy and nucleopolyhedrovirus-infected Spodoptera frugiperda larvae was compared. C. rufilabris did not discriminate between healthy and virus-infected prey, although the mean search time was approximately two times longer towards virus-infected larvae. In contrast, D. taeniatum directed a greater proportion of their attacks towards virus-infected prey but there was no significant difference in the search time. Prey consumption time did not differ significantly for each type of prey by either predator, although prey consumption was much faster in D. taeniatum. Viable virus was detected in D. taeniatum faeces up to 3 d after feeding on infected S. frugiperda larvae, whereas virus was inactivated in the gut of C. rufilabris. Both predators were shown to have acidic guts. A field experiment demonstrated that D. taeniatum that had fed on infected prey could contaminate foliage resulting in the transmission of the disease at a low prevalence (4.7%) to S. frugiperda larvae in a field maize crop.
Journal of Economic Entomology, 2004
were performed to determine the efÞcacy of maize ßour-based granular formulations with ultralow r... more were performed to determine the efÞcacy of maize ßour-based granular formulations with ultralow rates of the naturally derived insecticide spinosad (0.1, 0.3, and 1.0 g [AI]/ha), for control of Spodoptera frugiperda (J.E. Smith) in maize, Zea mays L., in southern Mexico. Spinosad formulations were compared with a chemical standard, a commercial granular formulation of chlorpyrifos (150 g [AI]/ha). In both years, application of spinosad resulted in excellent levels of control, indicated by the number of living S. frugiperda larvae recovered from experimental plots. The efÞcacy of spinosad applied at 0.3 and 1.0 g (AI)/ha was very similar to that of chlorpyrifos. Natural reinfestation caused S. frugiperda numbers in insecticide treated plots to return to values similar to the control treatment by 10 Ð15 d postapplication. Many spinosad-intoxicated larvae collected in the Þeld died later in the laboratory in 2002, but not in 2003. Percentage mortality due to parasitoid emergence did not differ in any treatment in either Þeld trial. The number of parasitoids that emerged from S. frugiperda collected in each treatment was signiÞcantly reduced after application of spinosad (all rates) or chlorpyrifos due to a reduction in the number of host larvae. Parasitoid numbers returned to control values by 9 Ð15 d postapplication in all treatments. The most prevalent parasitoid was the braconid Chelonus insularis Cresson, which represented Ϸ80% of emerging parasitoids in both years. We conclude that appropriate formulation technology can greatly enhance the performance of this naturally derived, biorational insecticide.