Archytas Marmoratus Research Articles

Parasitismo Natural de Spodoptera frugiperda1 en Maíz en la Comarca Lagunera, México

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is the insect pest of great economic importance because of damage to maize (Zea mays L.) worldwide. The parasitoid species of S. frugiperda and the degree of natural parasitism in maize from the Comarca Lagunera located at Coahuila and Durango, Mexico, were determined. Egg parasitism was low, 4.7% in 2020 and 2.0% in 2021, mostly because of Trichogramma spp. Larval parasitism was 20.6% in 2020 and 59.7% in 2021. Nine species of larval parasitoids identified were: Chelonus insularis (Cresson), Chelonus cautus (Cresson), Pristomerus spinator (Fabricius), Campoletis sonorensis (Cameron), Aleiodes laphygmae (Vierechk), Ophion flavidus Brulle, Euplectrus platyhypenae Howard, Lespesia archippivora (Riley), Archytas marmoratus (Townsend), and Aleiodes laphygmae. The latter is a new report for the State of Durango. These results are a contribution to knowledge of natural parasitism of fall armyworm in the Comarca Lagunera, establishing the basis for future studies of its biological control.

Biology, Ecology and Ipm of Fall Army Worm <I>Spodoptera Frugiperda </I> (J E Smith): A Review

The fall armyworm, Spodoptera frugiperda (J E Smith) is an emerging polyphagous pest. Its primary food is the corn cob, which suffers significant damage with its larvae skeletonizing or “windowing” the leaves. Only the larval stage is seriously risky and small and large communities as well as researchers have used a variety of control methods A number of low-cost mitigation strategies are available and these strategies include encouraging smallholder farmers to plant crops directly after major rainstorms, using cultural methods, such as intercropping and crop rotation, and avoiding some of the ineffective insecticides. Understanding the function of natural enemies in agricultural systems requires monitoring them in the field. Chelonus insularis, Pristomerus spinator, Cotesia marginiventris, Meteorus laphygmae, Chelonus sonorensis, Orius insidiosus, Chelonus texanus, Archytas marmoratus, Elenomus remus, and Trichogramma spp. are parasitoids of S. frugiperda Metarhizium anisopliae, Erynia radicans, Fusarium solani, Nomuraea rileyi and Beauveria bassiana are the main entomopathogenic fungi. These biocontrol agents should be promoted to manage this pest in a sustainable manner.

Parasitoides associados com Helicoverpa armigera em áreas de refúgio de algodão, no Oeste da Bahia, Brasil

ABSTRACT: Natural biological control is one of the major causes responsible for reduction of pest population in agricultural ecosystem. However, natural biological control importance is usually minimized by not being estimated. This study reports the occurrence of Campoletis sonorensis (Cameron, 1886) (Hymenoptera: Ichneumonidae), Archytas marmoratus (Townsend, 1915) and Archytas incertus (Macquart, 1851) (Diptera: Tachinidae) associated with Helicoverpa armigera (Hübner, 1809) (Lepidoptera: Noctuidae). The rate of larval parasitism was up to 41% in structured refuge areas of cotton, without chemical control with insecticides. This study strengthens our knowledge relating to parasitoids associated with natural control of H. armigera in the American continent. In addition, it documents the rule that structured refuge areas could play as a source of natural enemies, besides their contribution to production of non-selective populations to Bt technology.

Occurrence of Natural Enemies ofSpodoptera frugiperda(Lepidoptera: Noctuidae) in Chihuahua, Mexico

All instars of fall armyworm (FAW), Spodoptera frugiperda Smith & Abbot (Lepidoptera: Noctuidae), were collected in maize (corn) fields in 5 localities of the state of Chihuahua, Mexico, in 2014, with the main objectives of identifying its natural enemies and estimating the level of parasitism. Larvae were maintained under controlled conditions, fed with artificial diet, and observed daily until the emergence of parasitoids, until the appearance of mycosis, nematodes, or typical symptoms of baculoviral infection, or until they reached adulthood. Out of 5,870 larvae collected, 1,068 were attacked by natural enemies (parasitoids and entomopathogens), representing a total incidence of 18.2%. The incidence of parasitism by parasitoids was 8.1%, and parasitoids emerged from 5.8% of the larvae. The parasitoids found were: Chelonus insularis Cresson and Meteorus arizonensis Muesebeck (Hymenoptera: Braconidae); Campoletis sonorensis (Cameron), Campoletis flavicincta (Ashmead), Pristomerus sp. (Hymenoptera: Ichneumonidae); Euplectrus platyhypenae Howard (Hymenoptera: Eulophidae); and Lespesia sp. and Archytas marmoratus (Townsend) (Diptera: Tachinidae). Meteorus arizonensis and C. flavicincta were the most commonly encountered parasitoids, affecting 3% and 1.3% of the total collected larvae, respectively. Also, 2 species of entomopathogenic fungi were found: Metarhizium rileyi (Farl.) Kepler, S.A. Rehner & Humber comb. nov. (= Nomuraea rileyi [Farl.] Samson; Hypocreales: Clavicipitaceae) and Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae), with incidences of 8.6% and 0.65%, respectively. Forty-nine nucleopolyhedrovirus (Baculoviridae) isolates were obtained, corresponding to an incidence of 0.8%. Also, 0.07% of larvae were infected by entomopathogenic nematodes. In addition to the parasitoids and pathogens obtained, 34 specimens of the predator Podisus maculiventris (Say) (Hemiptera: Pentatomidae) were found during the surveys.

Parasitoids and Entomopathogens of the Fall ArmywormSpodoptera frugiperda(Lepidoptera: Noctuidae) in Nayarit, Mexico

Thirteen-hundred larvae of Spodoptera frugiperda were collected from infested maize fields in Nayarit in 2011 and 2012. These larvae were examined for natural enemies. Six parasitoid species were found and identified such as Cotesia sp. (0.3%) and Chelonus insularis (3.9%) (Hymenoptera: Braconidae), Pristomerus spinator (1.1%), Campoletis sp. (0.3%) and Hyposoter sp. (0.1%) (Hymenoptera: Ichneumonidae), and one tachinid fly Archytas marmoratus (0.07%) (Diptera: Tachinidae). Also two entomopathogenic fungi were isolated: Beauveria bassiana (3.7%) and Nomuraea rileyi (8.9%), and one nucleopolyhedrovirus (11%) SfMNPV (Baculoviridae). Total percentage of parasitism was 29.7%, which generates a potential use in biological control programs by conservation.

Natural Distribution of Parasitoids of Larvae of the Fall Armyworm,Spodoptera frugiperda, in Argentina

To develop a better understanding of the natural distribution of the fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae), and to update the knowledge of the incidence of its complex of parasitoids. S. frugiperda, samplings in whorl-stage corn were carried out in provinces of Argentina from 1999 to 2003. S. frugiperda larvae were collected from corn in localities of the provinces of Tucumán, Salta, Jujuy, Santiago del Estero, La Rioja, Córdoba, San Luis, Chaco and Misiones. In each locality 30 corn plants were sampled and only larvae located in those plants were collected. The parasitoids that emerged from S. frugiperda larvae were identified and counted. The abundance of the parasitoids and the parasitism rate were estimated. The S. frugiperda parasitoids collected were Campoletis grioti (Blanchard) (Hymenoptera: Ichneumonidae), Chelonus insularis (Cresson) (Hymenoptera: Braconidae), Archytas marmoratus (Townsend) (Diptera Tachinidae) and/or A. incertus (Macquart), Ophion sp. (Hymenoptera: Ichneumonidae), Euplectrus platyhypenae Howard (Hymenoptera: Eulophidae), and Incamyia chilensis (Aldrich) (Diptera Tachinidae). C. grioti was the most abundant and frequent during the five-year survey. Similar diversity of parasitoids was obtained in all the provinces, with the exception of I. chilensis and E. platyhypenae that were recovered only in the province of Salta. In the Northwestern region, in Tucumán, C. grioti and species of Archytas were the most abundant and frequent parasitoids. On the contrary, in Salta and Jujuy Ch. insularis was the parasitoid most abundant and frequently recovered. The parasitism rate obtained in Tucumán, Salta and Jujuy provinces were 21.96%, 17.87% and 6.63% respectively with an average of 18.93%. These results demonstrate that hymenopteran and dipteran parasitoids of S. frugiperda occurred differentially throughout the Argentinian provinces and played an important role on the natural control of the S. frugiperda larval population.

Mortality of the Corn Earworm (Lepidoptera: Noctuidae) on Sorghum Panicles in Georgia

The mortality of the corn earworm, Helicoverpa zea (Boddie), on sorghum panicles in Georgia was determined in a 2-yr study. Percent total real mortality (rx) of H. zea exceeded 99% for each year and planting date. Percent total real mortality was highest for eggs followed by 1st instars. Parasitization and predation were the primary mortality factors for eggs on sorghum panicles. Larval mortality was due in part to predation, parasitization, and infection by pathogens. Trichogramma pretiosum Riley was the only egg parasitoid observed on sorghum panicles. Orius insidiosus (Say) was the predominant predator of H. zea. Other predators observed feeding on H. zea included the big-eyed bug, Geocoris punctipes (Say), the spined soldier bug, Podisus maculiventris (Say), green lynx spiders, Peucetia viridans (Hentz), and lady beetles (mainly Hippodamia convergens Guérin-Méneville). A variety of parasitoids attacked larvae on sorghum. The braconid Cotesia marginiventris (Cresson) parasitized small to medium-sized larvae. The tachinids Eucelatoria rubentis Coquillett and Archytas marmoratus (Townsend) parasitized large larvae. Two pathogens, HzNPV, a naturally-occurring nuclear polyhedrosis virus of H. zea, and the fungus, Entomophthora aulicae (Reichardt) G. Winter, caused mortality of larvae. In conclusion, biological control by natural enemies of H. zea on sorghum panicles resulted in significant mortality for this pest.

Survival of Archytas marmoratus (Diptera: Tachinidae) in Helicoverpa zea and Spodoptera frugiperda (Lepidoptera: Noctuidae) at Low Temperatures and Short Days

Archytas marmoratus (Townsend) was reared on corn earworm, Helicoverpa zea (Boddie), or fall armyworm, Spodoptera frugiperda (J. E. Smith). Rearing chambers were programmed for a constant temperature of 15, 16, 19, 20, 22, 24, or 25°C and a photoperiod of 10:14 h (L:D) or 25°C and a photoperiod of 12:12 h (L:D). Development of parasitoids was faster when corn earworm larvae were parasitized than when fall armyworm larvae were parasitized. At 15°C parasitoid survival was poor on both hosts but at 16°C, more parasitoids eclosed on corn earworm than fall armyworm. Diapause induction in this strain of corn earworm was low. All pupae that eclosed after being in diapause produced an adult corn earworm. The data suggested that A. marmoratus is not influenced by diapause induction in its host but continues to develop above the threshold temperature for survival. This would restrict its overwintering as a larva or pupa to regions that have a continuous, nondiapausing host population. Thus, yearly establishment of A. marmoratus in more temperate areas would be required.

Levantamento dos inimigos naturais da lagarta do cartucho do milho, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), na região de Cascavel, PR

A survey of the natural enemies of S. frugiperda larvae was done during the years of 1992/93 and 94/95, in Cascavel region, Parana State. The most frequent parasitoids were Campoletis sp. (Hymenoptera: Ichneumonidae), which reached 47.0% of parasitism and Archytas marmoratus (Diptera: Tachinidae), which reached 15.4%. Of all Baculovirus found, 10.8% were NPV (nuclear polihedrosis virus) and only 1% was GV (granulosis virus).

Archytas marmoratus (Diptera: Tachinidae) Survival in Diapausing and Nondiapausing Strains of Helicoverpa zea (Lepidoptera: Noctuidae)

Archytas marmoratus (Townsend) was reared on four strains of corn earworm, Helicoverpa zea (Boddie). One strain did not diapause or entered a weak diapause. A portion of the other three strains entered diapause when reared at 19 or 22°C and 10:14 h photoperiod (L:D). No A. marmoratus entered diapause; 90% eclosed with no differences among strains or rearing condition, and the number of days from host pupation to eclosion within rearing condition was similar regardless of host strain. Parasitized pupae did not enter a chill-terminated diapause, as indicated by loss of larval eyespots within 2 wks. Either the presence of A. marmoratus maggots prevented diapause in its host or diapause was terminated by rapid development of the maggot after host pupation. These data suggest that A. marmoratus does not overwinter as a larva or pupa in the cooler regions of its distribution.

Inundative Release of Archytas marmoratus (Diptera: Tachinidae) Against the Corn Earworm and Fall Armyworm (Lepidoptera: Noctuidae) in Whorl-Stage Corn

A 3-yr pilot test was conducted to determine the feasibility of controlling early-season populations of corn earworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda (J. E. Smith), by augmentative releases of the tachinid parasitoid Archytas marmoratus (Townsend). Percentage parasitism of corn earworm larvae was increased to 42% in non-isolated fields of whorl-stage corn and >90% in isolated fields by inundative releases (≈1500 A. marmoratus ♀♀ per ha per week). Fall armyworm larvae were parasitized at a much lower level than corn earworm larvae. In a contiguous corn growing area, there was a positive correlation between density of corn earworm larvae and percentage parasitism within 0.8 km of the release field. The field with the greatest larval density and percentage parasitism of corn earworm larvae was the one farthest from the release site, indicating good host finding capability by A. marmoratus. These results show that inundative releases of this parasitoid could become an important component of integrated management strategies against early-season populations of corn earworm and fall armyworm. The high percentage of superparasitism in corn earworm larvae suggests that the release rate of A. marmoratus will need to be adjusted to host larval density.

Effects of linear furanocoumarins on the herbivore Spodoptera exigua and the parasitoid Archytas marmoratus: host quality and parasitoid success

AbstractWe assessed the effects of three photoactivated linear furanocoumarins, secondary plant metabolites present in Apium spp. (Apiaceae) and other taxa, on the larval‐pupal parasitoid, Archytas marmoratus (Townsend) (Diptera: Tachinidae) and the host Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), in the presence and absence of ultraviolet radiation. These results then were compared with previously described responses of Archytas marmoratus and other hosts to different plant allelochemicals. Ultraviolet radiation had no consistent detrimental effects. Increasing concentrations of linear furanocoumarins (from 0 to 0.029% of fresh weight) increased mortality of both the host and parasitoid. Increasing linear furanocoumarin levels also prolonged larval development of surviving S. exigua, but had no effect on pupal developmental time or pupal mass. Consequently, there was no effect of increasing linear furanocoumarin levels on surviving parasitoid development time (from the time of host pupation) or size. These results indicate the effects of linear furanocoumarins are mediated through effects on the host. Because reported responses of Ar. marmoratus to other allelochemicals (e.g., flavones, methyl ketones) are mediated through host effects, these results support the hypothesis that Ar. marmoratus displays a generalized response to plant allelochemicals that are predictable based on host mediated effects.

Superparasitism and Intraspecific Competition by the Solitary Larval-Pupal Parasitoid Archytas marmoratus (Diptera: Tachinidae)

Superparasitism and intrinsic larval competition by the solitary larval-pupal parasitoid Archytas marmoratus (Townsend) were studied in vivo. In superparasitized hosts, when two parasitoids entered a host pupa, only one parasitoid completed development. The surviving A. marmoratus maggot eliminated the conspecific competitor through physiological suppression during the second stadium of the supernumerary maggot. Supernumerary parasitoids never survived beyond the second instar, regardless of the time interval between initial parasitism and subsequent superparasitism. Physical combat was not evident because the parasitoid eliminated did not show signs of physical injuries. Scramble competition for host resources was not a probable mechanism of elimination because puparial weights and adult eclosion rates from superparasitized host pupae, and those from singly parasitized pupae, were not signif-icantly different.

Integration of Inherited Sterility and a Parasitoid, Archytas marmoratus (Diptera: Tachinidae), for Managing Helicoverpa zea (Lepidoptera: Noctuidae): Acceptability and Suitability of Hosts

One of the factors important to the successful integration of inherited sterility and biological control is the suitability of hosts from irradiated parents. In this study corn earworm, Helicoverpa zea (Boddie), larvae from irradiated parents were compared with larvae from normal parents as to their acceptance by and suitability for Archytas marmoratus (Townsend). Normal larvae and larvae from crosses of irradiated males with normal females were placed in whorl-stage com and subsequently exposed to maggots of A. marmoratus. Host and parasitoid emergence was approximately equal from both the normal and the irradiation treatment; however, parasitism was greater in the normal hosts. In field-cage studies in which adult A. marmoratus were released and allowed to larviposit, percentage parasitism and emergence of H. zea and A. marmoratus were equal between the normal treatment and the irradiation treatment. When maggots were applied to caged plants, emergence of H. zea and A. marmoratus were both low. Significantly more H. zea emerged in the normal treatment than in the irradiation treatment and the application of maggots did not affect emergence of H. zea. There were no significant differences in emergence of A. marmoratus between the normal and irradiation treatments. In a concurrent laboratory study, emergence of H. zea did not differ between normal and irradiation treatment but was greatly reduced when exposed to maggots. Similarly, emergence of A. marmoratus was not affected by irradiation treatment. Larvae from a cross of irradiated males and normal females appear to be both acceptable and suitable for development and subsequent emergence of A. marmoratus.

Host Corn Earworm (Lepidoptera: Noctuidae) Reared on Meridic Diet Containing Silks from a Resistant Corn Genotype on Archytas marmoratus (Diptera: Tachinidae) and Ichneumon promissorius (Hymenoptera: Ichneumonidae)

Larvae of Helicoverpa zea (Boddie) fed on a meridic diet containing silks of a resistant corn genotype, ‘Zapalote Chico 2451# (PC3)’, were examined as suitable hosts for a larval–pupal parasitoid, Archytas marmoratus (Townsend), and a pupal parasitoid, Ichneumon promissorius (Erich). Host pupal weight, parasitoid weight, and developmental time were significantly reduced when host larvae were reared on a diet containing resistant silks compared with diet without resistant silks. Weight of A. marmoratus was strongly correlated with host weight for both host diets. Parasitoid developmental time for both parasitoids was also correlated with host pupal weight for hosts fed on a diet containing resistant silks. Fecundity of both parasitoids was not affected by host diet. Adult longevity of I. promissorius was significantly reduced when reared from hosts fed the diet containing resistant silks compared with hosts reared on the diet without resistant silks. Longevity of female A. marmoratus was not affected by host diet, but male A. marmoratus lived longer when reared from hosts fed the resistant diet. Despite a few negative effects (lower percentage emergence of A. marmoratus ) of a resistant host diet on the parasitoids, these strategies could be compatible because the negative effects did not result in lower parasitoid fecundity or increased parasitoid developmental time.

Distribution of Fall Armyworm (Lepidoptera: Noctuidae) Parasitoids on Five Corn Genotypes in South Georgia

Five genotypes of corn were planted on four different dates in south Georgia during the spring of 1991. Plants were infested with neonate fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), larvae and collected either seven or twelve days later. Larvae were reared in the laboratory on artificial diet to determine distribution of FAW parasitoids. Larvae recovered from the resistant genotype MpSWCB-4 had the highest percent parasitism (44.30%), while the susceptible genotype Pioneer 3192 had the lowest parasitism (31.70%). Aleiodes laphygmae (Gahan) was the most abundant parasitoid, attacking a total of 12.8% of the 16,120 FAW larvae recovered. Archytas marmoratus (Townsend) parasitized 10.0% of the FAW larvae while Ophion flavidus Brulle and Cotesia marginiventris (Cresson) parasitized 7.9% and 6.3%, respectively, of the recovered FAW. Ten additional parasitoid species emerged from the FAW, but none of these species attacked more than 1% of the recovered FAW larvae.

Influence of Helicoverpa zea (Lepidoptera: Noctuidae) Age During the Last Instar on Rates of Parasitization by the Larval-Pupal Parasitoid, Archytas marmoratus (Diptera: Tachinidae)

Effects of host age during each of the 5 d of the last host instar were determined by exposing larvae of Helicoverpa (= Heliothis ) zea (Boddie) to newly larviposited maggots of the larval-pupal parasitoid Archytas marmoratus (Townsend). Based on determinations made in host pupae, lower percentages of older hosts were parasitized and lower percentages of maggots from older hosts developed to the second ins tar. Weights of maggots that parasitized older hosts were lower in 1-d-old host pupae. For older hosts, mean length of the larval stage of A. marmoratus after host pupation was longer; weights of young A. marmoratus larvae revealed that maggots developed very slowly until just before the host pupated. Surviving maggots developing from older hosts used the longer developmental times to overcome the weight differentials, and weights of A. marmoratus pupae were the same regardless of host age and parasitoid weight at the beginning of the host's pupal stage. These and other data indicate that complex behavior allows the A. marmoratus maggot to evade host defenses and grow to a size that enables the parasitoid to avoid encapsulation when it finally enters the host hemocele.

Incidence of Fall Armyworm (Lepidoptera: Noctuidae) Parasitoids on Resistant and Susceptible Com Genotypes

Fall armyworm, Spodoptera frugiperda (J. E. Smith), larvae were collected from 24 May to 28 August 1990 and from 20 May to 17 June 1991 to determine parasitoid distribution of fall armyworm on resistant and susceptible com genotypes. Resistant corn genotypes were ‘MpSWCB-4’ and ‘Pioneer X304C’ and susceptible genotypes were ‘Pioneer 3192’ and ‘Cacahuacintle X’s'. In 1990, Cotesia marginiventris (Cresson) was the most prevalent parasitoid in early season, parasitizing 34% of fall armyworm larvae, and it continued to be present in low numbers throughout the summer. On only one collection date (24 May 1990) did corn genotype have a significant effect on parasitism rates. On that date, significantly more C. marginiventris were reared from hosts obtained from resistant corn genotype ‘MpSWCB-4’ than from the other three genotypes. In 1991, Archytas marmoratus (Townsend) was the most abundant parasitoid, attacking an average of 13.6% of fall armyworm recovered. Corn genotype had a significant effect on the incidence of parasitism throughout 1991. Fall armyworm collected from the susceptible genotype ‘Pioneer 3192’ were parasitized significantly less frequently (8.3%) than were the larvae collected from the susceptible corn genotype ‘Cacahuacintle X’s' (9.8%) or the resistant genotype ‘MpSWCB-4’ (9.6%).

Seasonal Distribution, Response to Host Developmental Stage, and Screened-Cage Performance of Archytas marmoratus (Diptera: Tachinidae) and Ophion flavidus (Hymenoptera: Ichneumonidae) on Spodoptera frugiperda (Lepidoptera: Noctuidae)

Laboratory and field studies with Archytas marmoratus (Townsend) and Ophion flavidus Brulle were designed to provide a better understanding of their individual and combined impact on the fall armyworm, Spodoptera frugiperda (J. E. Smith). The highest percentage of natural parasitism by A. marmoratus and O. flavidus on S. frugiperda occurred from late April through mid-June during 1985-1986 near Tifton, Georgia. Ophion flavidus parasitized 4th, 5th, and 6th instars with equal success, but were minimally successful in completing development on late 6th instars. Archytas marmoratus were equally successful in completing development on 3rd, 4th, 5th, and 6th instars. When S. frugiperda were multiply parasitized, A. marmoratus did not successfully compete with O. flavidus. When two A. marmoratus and two O. flavidus females, or four A. marmoratus and four O. flavidus females were released against 5-6th instar S. frugiperda in whorl-stage corn within 1.8 @? 1.8 2? 1.8 m screened cages, the number of emerged S. frugiperda adults of the subsequent generation was reduced by 50.6 and 92.1%, respectively. With the development of economical methods for mass propagation of A. marmoratus and/or O. flavidus, will come primary opportunities for advancing biologically based strategies for managing S. frugiperda.

Field Release and Evaluation of Archytas marmoratus (Diptera: Tachinidae) Against Larvae of Heliothis zea (Lepidoptera: Noctuidae) in Whorl Stage Corn

Laboratory-reared adults of the tachinid parasitoid, Archytas marmoratus Townsend, were released and evaluated against larvae of Heliothis zea (Boddie) in whorl stage corn during 1986–1988. Resulting rates of parasitism by A. marmoratus on H. zea larvae occurring at 0.3, 0.5, and 1.0 per row-m were 58.3, 44.2, and 52.8%, respectively, when about 340 females/ha were released, and 45.9, 38.2, and 32.1%, respectively, when about 170 females/ha were released. In both studies, no significant differences ( P > 0.05) in rates of parasitism were found between host densities. The number of H. zea larvae parasitized by A. marmoratus increased linearly over the range of host densities studied. This suggests that per capita mortality is density-independent and, therefore, should not increase or decrease as host density is varied within the range of early season populations. A. marmoratus females appeared to disperse predominately into the prevailing wind. Rates of A. marmoratus parasitism were significantly higher (P < 0.05) on fourth and fifth instars than on third instars. Approximately 370 and 860 female A. marmoratus /ha would be needed to yield 50 and 80% parasitism of fourth and fifth instars of H. zea , respectively, in 9–14-leaf stage dent corn. Data suggest that A. marmoratus females are highly efficient in finding larvae of H. zea in whorl stage corn, and that rates of parasitism observed in the relatively small release areas are likely far lower than could be expected from sustained releases throughout large corn ecosystems wherein the effects of predominately unilateral movement from release areas would be minimized. With the development of economical methods of mass propagation, A. marmoratus likely could play a major role in the safe, efficient, and selective management of the early season populations of H. zea in whorl stage corn.