Incidence of superparasitism in the egg parasitoid,Ooencyrtus kuvanae Howard (Hymenoptera: Encyrtidae)

The encyrtid Ooencyrtus kuvanae is a solitary parasitoid of the gypsy moth, Lymantria dispar L. (Lepidoptera-Lymantridae) that is used in biological control programmes and whose mass rearing is influenced by superparasitism. The purpose of this study was to investigate the effect of the self-superparasitism of O. kuvanae at different host densities (5, 10, 15 and 20), female ages (3 and 5 days) and durations of exposure (1 and 5 days) under various laboratory conditions (25°C?±?1°C, RH 60?±?5% and a 16:8?h light:dark photoperiod) as well as in a new laboratory host, Philosamia ricini (Danovan) (Lepidoptera: Saturniidae) of O. kuvanae. In this study, we determined the rate of egg superparasitism and adult emergence and recorded development time, longevity and body weight. Superparasitism increased with female age and the duration of exposure to parasitoids when females had access to five host eggs. Superparasitism increased the number of parasitoid offspring, but it resulted in male-biased (56.90%) progeny. Furthermore, superparasitism caused deleterious effects to the fitness of the progeny by prolonging the developmental process, and decreasing longevity. For example, we found that when four adults can emerge from one superparasitised host egg, the body size of the parasitoid offspring decreases significantly. Hence, superparasitism should be avoided when mass rearing O. kuvanae.     

Optimal biological parameters for rearing Ooencyrtus pityocampae on the new laboratory host Philosamia ricini

Biological control programmes involving Ooencyrtus pityocampae Mercet (Hymenoptera: Encyrtidae) have proved effective at reducing the damage caused by the pine processionary Thaumetopoea pityocampa Denis & Schiffermüller (Lepidoptera: Thaumatopoeidae). In this study, the biological variables that influence the parasitism of O. pityocampae on the new laboratory host Philosamia ricini Danovan (Lepidoptera: Saturniidae) have been investigated. Laboratory experiments were conducted under the conditions of 25 ± 1°C, 65 ± 5% R.H (relative humidity) and a photoperiod of 16 : 8 h (L : D = light : dark). The host egg age and parasitoid age are often regarded as being key factors influencing the emergence rate of O. pityocampae. The optimal age of host eggs for parasitization was 1–2 days, and the emergence rate was highest with 5‐day‐old female parasitoids. Thus, our results define the optimal conditions for the effective and economic rearing of parasitoids as follows: one 5‐day‐old female parasitoid per 50 (1–2)‐day‐old host eggs. The development time of O. pityocampae ranged between 19.5 and 22.6 days. Parasitoids that were exposed to bio‐honey survived 10.5 times longer than those that did not receive supplemental food. O. pityocampae was reared for more than nine generations on the eggs of P. ricini. Consequently, P. ricini has been found as a suitable new laboratory host for the mass rearing of O. pityocampae for the use of biological control programmes against T. pityocampa in future.     

Study on some biological characteristics of Tetrastichus gallerucae (Hym. Eulophidae), important parasitoid of Elm leaf beetle eggs in Kerman,Iran

In this study, a number of biologic characteristics of Tetrastichus gallerucae, the most important natural enemy of Xanthogaleruca luteola (Col.: Chrysomellidae), were studied. Experiments were carried out in growth room with a temperature of 25°C±1°C, relative humidity of 60%±5% and light period of 16L:8D. The results demonstrated the following outcomes: without food and host egg, the longevity of male and female bees was respectively, 1.23 and 1.35 days. On the host egg, their longevities were 3.85 and 6.02 days, respectively. On rarefied honey their longevities were 14.04 and 24.74 days, respectively and on the host eggs together with rarefied honey, their longevities were 13.4 and 34.72 days, respectively. The average growth period times in the egg of elm leaf beetle of male and female bees were 12.97 and 12.63 days, respectively. The percentage of female bees decreases as the longevity of the insects increases. These bees lay eggs in the 1–9-day-old eggs of elm leaf beetle but 1-day-old eggs of the host are preferred by T. gallerucae.     

The reproductive capability of Ooencyrtus kuvanae reared on eggs of the factitious host Antheraea pernyi

Ooencyrtus kuvanae is a key egg parasitoid of Lymantria dispar (L.), an important defoliating pest in China and North America. We have developed mass rearing techniques for O. kuvanae and in this study compared the reproductive capacity of O. kuvanae when it was previously reared on the natural host, L. dispar or the factitious host, Antheraea pernyi Guerin‐Meneville. There was no significant difference in the oviposition period or total number of eggs laid between L. dispar‐reared and A. pernyi‐reared females. However, the mean number of offspring successfully emerging from those eggs was significantly larger from the A. pernyi‐reared females compared with L. dispar‐reared females. From this, we can conclude that, with respect to reproductive capability, eggs of A. pernyi are suitable factitious hosts for mass rearing of O. kuvanae.     

A modified DNA barcode approach to define trophic interactions between native and exotic pentatomids and their parasitoids

The establishment of invasive Halyomorpha halys (Stål) outside of its native range may impact native species assemblages, including other pentatomids and their scelionid parasitoids. This has generated interest in defining species diversity and host‐parasitoid associations in this system to better understand the impact of invasive alien species on trophic interactions in invaded regions. Information on scelionid–pentatomid associations in natural habitats is lacking, and species‐level identification of these associations can be tenuous using rearing and dissection techniques. Naturally occurring pentatomid eggs were collected in areas where H. halys has established in Canada and were analysed using a modified DNA barcoding approach to define species‐level trophic interactions. Identification was possible for >90% of egg masses. Eleven pentatomid and five scelionid species were identified, and trophic links were established. Approximately 70% of egg masses were parasitized; parasitism and parasitoid species composition were described for each species. Telenomus podisi Ashmead was the dominant parasitoid and was detected in all host species. Trissolcus euschisti Ashmead was detected in several host species, but was significantly more prevalent in Chinavia hilaris (Say) and Brochymena quadripustulata (Fabricius). Trissolcus brochymenae Ashmead and Tr. thyantae Ashmead were recorded sporadically. Parasitism of H. halys was 55%, and this species was significantly less likely to be parasitized than native pentatomids. The scelionid species composition of H. halys consisted of Te. podisi, Tr. euschisti and Tr. thyantae. Although these species cannot develop in fresh H. halys eggs, we demonstrate that parasitoids attempt to exploit this host under field conditions.     

Effects of persimmon tannin on survival and reproduction of Halyomorpha halys (Hemiptera: Pentatomidae)

Halyomorpha halys (Hemiptera: Pentatomidae) occurs in sweet persimmon orchards from late July to early September and its damage level is negligible before mid‐July. It rarely appears in persimmon orchards after mid‐September, but is easily found in soybean fields. From the phenological observation of H. halys, it is assumed that seasonal migration of H. halys to sweet persimmon orchards may be related to the content of soluble tannin in sweet persimmon fruits. The feeding preference of H. halys was evaluated on sweet and astringent persimmon fruits, and the effects of persimmon fruits and purified persimmon tannin were tested on the survival of H. halys. Numbers of visiting bugs and feeding spots on the fruits were significantly higher on sweet persimmon than those on astringent persimmon. There was no significant difference in survivorships of H. halys fed sweet persimmon and soybean. However, the number of eggs laid by sweet persimmon fed adult females was significantly lower than those fed soybean. The higher concentration of persimmon tannin caused higher mortality of H. halys. Male and female H. halys fed with 3% persimmon tannin showed the lowest survival. Longevities of male H. halys fed with 0, 0.01, 0.1 and 1% persimmon tannin were 14.9, 12.7, 14.5 and 16.3 days, respectively. However, males fed with 3% tannin lived only 6.4 days. The longevities of female H. halys were similar to those of male (10.1, 14.4, 13.8, 12.0 and 6.1 days for 0, 0.01, 0.1, 1 and 3% tannin concentration, respectively). These results suggest that H. halys invades sweet persimmon orchards during late July and early September when more suitable foods, e.g. soybean, are in short supply and sweet persimmon fruits become suitable for feeding (e.g. lower tannin content).     

Parasitism,host feeding and immature development of Encarsia formosa reared from Trialeurodes vaporariorum and Bemisia tabaci on Trialeurodes ricini

Encarsia formosa Gahan (Hymenoptera: Aphelinidae), a thelytokous parasitoid, is an important biological control agent of whiteflies because of its outstanding reproduction and host‐feeding ability. In this study, we evaluated the parasitism, host feeding and developmental time of E. formosa populations reared on Trialeurodes vaporariorum (Westwood) (EFT) or on Bemisia tabaci (Gennadius) (EFB) when different nymphal instars of the castor whitefly, Trialeurodes ricini (Misra), were offered as hosts, with an aim to understand the preference of the parasitoid on nymphal instars of T. ricini. Experiments were conducted on castor bean plants at 26 ± 2°C, 50–60% RH and 16 : 8 (L : D) photoperiod. The results showed that E. formosa successfully oviposited and fed on all nymphal instars of T. ricini. However, numbers of the first instars fed on by the E. formosa populations reared on T. vaporariorum (EFT) and B. tabaci (EFB) were significantly greater (45.9 and 31.3, respectively) than those of the second (EFT: 30.4 and EFB: 15.8), the third (EFT: 22.4 and EFB: 13.2) and the fourth nymphal instars (EFT: 6.0 and EFB: 3.8). The number of T. ricini nymphs parasitized by E. formosa varied significantly among different instars, and the parasitism rates on the first instar (EFT: 15.2; EFB: 7.7) and fourth instar (EFT: 19.3; EFB: 4.9) were greater than those on the second and third instars. Encarsia formosa reared on T. vaporariorum had a significantly higher host feeding and ovipositing potential on T. ricini than EFB. When parasitizing the fourth instar nymphs, E. formosa completed development in a significantly shorter time (12.9 day) than when ovipositing in other instars (17.8–19.1 day). These results showed that EFT had a better host adaption than EFB. The information from this study should be useful for us to better understand the performance and nymphal preference of E. formosa from T. vaporariorum and B. tabaci when they parasitized and fed on T. ricini, and the interactions of parasitoids with different host whitefly species.     

Measuring host plant selection and retention of Halyomorpha halys by a trap crop

Trap cropping may exploit a pest's dispersal and host selection behavior in order to protect a desired crop. Here, we used a combination of visual sampling, immunomarking, and harmonic radar to assess host plant selection and retention time of the highly mobile and invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), as it moves within and between a polyculture trap crop of sorghum and sunflower, and a bell pepper cash crop. Visual sampling demonstrated no significant differences in H. halys densities across crops, whereas dislodging stink bugs to collect for protein analysis revealed ca. 4× more bugs in the trap crop plants than in the peppers. In total 145 H. halys were collected and of these 6% were doubly marked with proteins, demonstrating that minimal movement occurred between the two planting systems. Tracking tagged H. halys with harmonic radar revealed that the trap crop retained adult H. halys within the plots 1.5× longer and reduced their movement by nearly half compared with bugs released in the pepper cash crop. The data suggest the trap crop of sunflower plus sorghum has the potential to attract and arrest the invasive H. halys, demonstrating that trap cropping may operate as an effective management tool.     

Production of Anagrus epos Girault (Hymenoptera: Mymaridae) on Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs

Anagrus epos Girault (Hymenoptera: Mymaridae) is a natural enemy candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology or ecology of A. epos when it utilizes GWSS eggs as a host. Here, we report the results of laboratory studies that describe the host age preference for oviposition, longevity of A. epos adults provided with different food sources, and developmental rates at six different constant temperature regimes. Anagrus epos is a gregarious parasitoid in GWSS eggs with up to 14 adults emerging from each GWSS egg. In choice and no-choice tests for oviposition, A. epos females successfully parasitized all developmental ages of GWSS eggs (1–8 days old). In choice tests, parasitism rates were significantly higher in 1-, 3-, 4-, and 5-day-old GWSS eggs than in 2-, 6-, 7-, and 8-day-old eggs. If provided with honey and water, honey only, water only, or no food or water, A. epos females lived on average 8.2, 4.7, 2.6, and 1.6 days, respectively. Anagrus epos required 294.1 degree-days above a lower temperature threshold of 12.4 °C to develop from egg to adult (eclosion). Our results provide baseline information useful in the development of an efficient parasitoid mass rearing program for A. epos release and evaluation in California.     

Effects of the mixed biocide Bacillus thuringiensis–abamectin on the development of the parasitoid Microplitis mediator and its host Helicoverpa armigera

The effects of the mixed biocide Bacillus thuringiensis Berliner with abamectin (BtA) on the development of the parasitoid Microplitis mediator (Haliday) (Hymenoptera: Braconidae) and its cotton bollworm host, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), were evaluated in the laboratory. Weight gain in larvae of H. armigera was initially delayed, but larval developmental period increased and pupal weight increased when they were fed on a diet containing BtA. Due to increased longevity of the host larvae, the susceptible period to parasitization of H. armigera by M. mediator increased when the host larvae were reared on diets containing BtA at concentrations of 0.5, 1, 2, and 4 μg g^?1. The longevity of female and male parasitoids significantly decreased when newly emerged wasps were fed a honey solution containing 200 μg ml^?1 BtA in comparison with those fed only a honey solution. Mean longevity was significantly prolonged when parasitoids were fed a honey solution and BtA–honey solution in comparison with those fed BtA–distilled water, distilled water, or nothing. There were no significant differences compared with the control in any biological characteristics for the offspring of female parasitoids fed the honey solutions containing BtA at concentrations of 50, 100, and 200 μg ml^?1; characteristics measured include the egg‐larval period, pupal weight, male and female pupal periods, adult fresh weight, and adult longevity. When female parasitoids parasitized host larvae that had been fed the diet containing BtA, their male and female pupal periods were significantly prolonged compared with the control (without BtA).     

Reproductive performance of Nesolynx thymus (Hymenoptera: Eulophidae), in relation to age of Musca domestica (Diptera: Muscidae)

An investigation was undertaken to record the influence of host age on the reproductive performance of Nesolynx thymus (Hymenoptera:Eulophidae). This is an indigenous, gregarious, ecto-pupal parasitoid of certain dipteran insects, including the tachinid fly, Exorista bombycis (Louis) which is a well-known endo-larval parasitoid of the silkworm, Bombyx mori. Each gravid N. thymus female was allowed to parasitise 1–4-day-old puparia of Musca domestica L. for 2 days at a parasitoid–host ratio of 1:20. The parasitised host puparia were observed for progeny recovery, sex ratio, female longevity and fitness (adult size). In addition, reproductive performance of the parasitoid progeny was assessed by allowing its females to parasitise for 2 days, 3-day-old puparia of E. bombycis at a parasitoid–host ratio of 1:4. There was a significant negative correlation between host age and parasitisation rate, parasitoid developmental duration, sex ratio and female longevity while the correlation was positive between host age and parasitoid recovery per host puparium. Similarly, negative correlation was observed between host age and morphometric parameters (body length, head width and wing span of male and female and length and width of female abdomen) of the progeny adults. Host age did not have any impact on the reproductive performance of progeny adults when allowed to parasitise puparia of E. bombycis.     

Effects of Rag1 aphid‐resistant soybean on mortality,development, and preference of brown marmorated stink bug

The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), poses a new threat to soybean, Glycine max (L.) Merrill (Fabaceae), production in the north central USA. As H. halys continues to spread and increase in abundance in the region, the interaction between H. halys and management tactics deployed for other pests must be determined. Currently, the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is the most abundant and damaging insect pest of soybean in the region. Aphid‐resistant soybean, mainly with the Rag1 gene, is commercially available for management of A. glycines. Here, experiments were performed to evaluate the effects of Rag1 aphid‐resistant soybean on the mortality, development, and preference of H. halys. In a no‐choice test, mortality of H. halys reared on Rag1 aphid‐resistant soybean pods was significantly lower than when reared on aphid‐susceptible soybean pods (28 vs. 53%). Development time, adult weight, and proportion females of surviving adults did not differ when reared on Rag1 aphid‐resistant or aphid‐susceptible soybean pods. In choice tests, H. halys exhibited a preference for Rag1 aphid‐resistant over aphid‐susceptible soybean pods after 4 h, but not after 24 h. Halyomorpha halys exhibited no preference when tested with vegetative‐stage or reproductive‐stage soybean plants. The preference by H. halys for Rag1 aphid‐resistant soybean pods and the decreased mortality when reared on these pods suggests that the use of Rag1 aphid‐resistant soybean may favor this emerging pest in the north central USA.     

Surveying native egg parasitoids and predators of the invasive Halyomorpha halys in Northern Italy

The invasive Halyomorpha halys (Heteroptera: Pentatomidae) is a key pest of fruits in the Emilia‐Romagna region of Italy. For the development of a sustainable management programme, knowledge of its native natural enemy community and its efficacy is essential. A three‐year field survey was conducted exposing H. halys egg masses in different types of habitats to investigate the efficacy of native natural enemies in reducing the H. halys populations in the Emilia‐Romagna region, where the stinkbug was first detected in 2012. Over the first year of the study, sentinel eggs from laboratory cultures were stapled to the underside of leaves in various host trees, whereas in following years H. halys adults were directly caged on branches in sleeve cages to allow natural oviposition. Over the examined years, low rates of parasitism (1%–3%) and predation (2%–5%) were observed. Parasitism was caused exclusively by the generalist parasitoid Anastatus bifasciatus.     

Winter and spring ecology of <Emphasis Type="Italic">Anaphes nitens</Emphasis>, a solitary egg-parasitoid of the <Emphasis Type="Italic">Eucalyptus</Emphasis> snout-beetle <Emphasis Type="Italic">Gonipterus scutellatus</Emphasis>

We investigated the effects of temperature, photoperiod, food and host availability, and body size on the overwintering abilities of the egg parasitoid Anaphes nitens Girault (Hymenoptera, Mymaridae) under natural conditions. Seven groups of eighty females received one of four treatments (n = 20): (i) honey and hosts, (ii) water and hosts, (iii) honey, or (iv) water. Seven groups of forty males received only honey or water (n = 20). To test if short day-length is the main cue for larval dormancy, the experiment was replicated inside a climate chamber at 20°C and under a winter photoperiod. A. nitens overwinters because of quiescence or oligopause inside the hosts and increased adult longevity. Mean pre-emergence mortality was up to 26% indoors and 15.2% outdoors, males being more affected. Development time had a significant and positive effect on body size. Honey-fed females without hosts had the highest longevity (53 days). Mother’s diet and size affected development time, body size, longevity, and fecundity of the progeny. The results confirm the good adaptation of the parasitoid to the environmental conditions of NW Spain and its ability to synchronize its life cycle with the phenology of the host. Handling editor: Drik Babendreier.     

A molecular tool to identify Anastatus parasitoids of the brown marmorated stink bug

Globally, Anastatus species (Hymenoptera: Eupelmidae) are associated with the invasive agricultural pest Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). In Europe, the polyphagous Anastatus bifasciatus (Geoffroy) is the most prevalent native egg parasitoid on H. halys eggs and is currently being tested as a candidate for augmentative biological control. Anastatus bifasciatus frequently displays behavior without oviposition, and induces additional host mortality through oviposition damage and host feeding that is not measured with offspring emergence. This exacerbates accurate assessment of parasitism and host impact, which is crucial for efficacy evaluation as well as for pre‐ and post‐release risk assessment. To address this, a general Anastatus primer set amplifying a 318‐bp fragment within the barcoding region of the cytochrome oxidase I (COI) gene was developed. When challenged with DNA of three Anastatus species —A. bifasciatus, Anastatus japonicus Ashmead, and Anastatus sp.—, five scelionid parasitoid species that might be encountered in the same host environments and 11 pentatomid host species, only Anastatus DNA was successfully amplified. When applied to eggs of the target host, H. halys, and an exemplary non‐target host, Dendrolimus pini L. (Lepidoptera: Lasiocampidae), subjected to host feeding, no Anastatus amplicons were produced. Eggs of the two host species containing A. bifasciatus parasitoid stages, from 1‐h‐old eggs to pupae, and emerged eggs yielded Anastatus fragments. Confirmation of parasitoid presence with dissections and subsequent PCRs with the developed primer pair resulted in 95% success for 1‐h‐old parasitoid eggs. For both host species, field‐exposed sentinel emerged eggs stored dry for 6 months, 100% of the specimens produced Anastatus amplicons. This DNA‐based screening method can be used in combination with conventional methods to better interpret host‐parasitoid and parasitoid‐parasitoid interactions. It will help address ecological questions related to an environmentally friendly approach for the control of H. halys in invaded areas.     

Comparative study of development parameters of four Ooencyrtus spp. (Hymenoptera: Encyrtidae) on natural and factitious hosts

Biological control approaches such as seeding and augmentation releases of populations of natural enemies mostly rely on the indoor production of predator or parasitoid species, often with the use of alternative prey/host species. In this study, we investigated several development parameters of four egg parasitoid species: Ooencyrtus fecundus, O. near fecundus, O. pityocampae and O. telenomicida, and compared their performance on their natural host, the variegated caper bug (CB) Stenozygum coloratum, and on an alternative, factitious host, the silk moth (SM) Bombyx mori. Survival was higher and development duration shorter in CB eggs, making the CB a better host for these congeners. However, adult longevity was generally longer for individuals that developed in SM eggs. Moreover, O. fecundus and O. pityocampae females that had developed in SM eggs displayed higher fecundity than all other female/host combinations. Survival also varied according to the age of the SM eggs: parasitoid survival rates were significantly higher in 9‐ to 12‐month‐old (post‐diapausing) eggs than in young (about 1 month old) ones. These results were probably influenced by differences among the egg sizes of the studied hosts. The number of non‐laying females and self‐superparasitism rates were exceptionally high in O. near fecundus. These findings suggest that SM eggs, and especially those which are being utilized after a long storage, could serve for mass rearing of the studied Ooencyrtus spp.     

Laboratory evaluation of Orthocentrus brachycerus (Hymenoptera: Ichneumonidae), as a potential biological control agent in mushroom cultivation

Fungus gnats in the genus Neoempheria Osten Sacken (Diptera: Mycetophilidae) are serious pests of the shiitake mushroom, Lentinula edodes (Berk.) Sing. (Agaricales: Omphalotaceae), a prize edible. Recently, we found that the parasitoid wasp Orthocentrus brachycerus Humala & Lee, 2020 (Hymenoptera: Ichneumonidae) attacks larvae of Neoempheria. We have shown in previous research that O. brachycerus suppresses population growth of Neoempheria in simulated cultivation conditions, and thus shows potential for use as a biological control agent. However, the behavioural and ecological aspects of this wasp have not been studied. Here, under controlled laboratory conditions, we investigated the fecundity, longevity and host stage specificity of O. brachycerus against Neoempheria larvae. We found that O. brachycerus are prolific throughout their life cycle. On average, female O. brachycerus made over 140 attempts to parasitize pest larvae, and over 90% of Neoempheria larvae were parasitized or died before emergence. Parasitoid females kept at 20°C survived for an average of 15.4 ± 3.58 days, and some females survived >30 days. Females continued to oviposit eggs throughout their life cycle and parasitized all stages of host larvae, but not eggs. These observations indicate that O. brachycerus may be effective for control of Neoempheria larvae in shiitake cultivation facilities. These results provide a basis for establishing a protocol for using O. brachycerus in mushroom cultivation.     

Host Location and Ovipositional Behavior of Platygaster demades Walker (Hymenoptera: Platygastridae), an Egg Parasitoid of Apple and Pear Leaf Curling Midges

The foraging responses of 1–2-day-old naïve female Platygaster demades to odors of apple and pear foliage and host insect eggs were measured. The host origin of P. demades had no effect on the parasitoids’ longevity, host preference, or foraging behavior. Four distinct behaviors related to oviposition were identified. In choice experiments, more female parasitoids responded to apple foliage with no midge eggs than to midge eggs alone. In a Y-tube olfactometer, parasitoids preferred the plant cues to clean air, and responded equally to both apple and pear odors. The results indicate that P. demades utilizes plant cues to locate the habitat of its host and then searches for host eggs to parasitize.     

Influence of adult diet on fitness and reproductive traits of the egg parasitoid Anagrus virlai (Hymenoptera: Mymaridae), a potential biocontrol agent against the corn leafhopper

Dalbulus maidis is the most important leafhopper pest of maize in the Americas. Anagrus virlai is an egg parasitoid commonly associated with the corn leafhopper. We evaluated whether the performance of A. virlai is dependent on different diets provided during 24 hr or throughout adult female lifetime. Additionally, functional response of A. virlai on D. maidis eggs using maize leaves containing honeydew plus honey was described. A. virlai is a mostly pro-ovigenic autogenic species whose females are able to parasitize eggs immediately after emergence. We found that wasps oviposit the majority of their eggs in the first day of their adult life. Realized lifetime fecundity and lifetime potential fecundity did not differ significantly among treatments, but longevity and egg production increased when honey was added to diet. Data were consistent with an intermediate functional response between type II and III, but closer to type II, indicating a high parasitism rate at low host densities and a decrease in the oviposition rate at high host densities, due to a possible egg limitation. Our results suggest that carbohydrate food sources (honeydew and honey) might not be the factor limiting reproductive success during the first 24 hr. Food supply, however, might influence egg maturation and survivorship of wasps, thus potentially enhancing biological pest control when hosts are scarce in the course of the first few days of adulthood.     

Life history characteristics of Orius insidiosus (Say) fed Aphis glycines Matsumura

The soybean aphid, Aphis glycines Matsumura, is a new invasive pest of soybeans throughout most of the soybean production areas of North America. Field studies have demonstrated that the indigenous predator, Orius insidiosus (Say), is an important natural enemy of the soybean aphid early the soybean crop season. Because soybean aphid is newly introduced into North America, the life history characteristics of predators fed this aphid are not known. In laboratory assays, we measured the survival, development, longevity and reproduction of O. insidiosus fed 1, 3, 6 or 12 seconds to third instars of soybean aphid. O. insidiosus nymphal development decreased from 34.0 to 21.4 days as the number of soybean aphid nymphs provided increased from 1 to 6 aphid nymphs daily. Stage-specific mortality was highest at 68% for first instar O. insidiosus nymphs fed 1 soybean aphid nymph per day. Adult longevity (43.9 days) and fecundity (49.7 eggs per female) was highest for O. insidiosus fed 6 soybean aphid nymphs daily, but longevity (23.5 days) and fecundity (10.1 eggs per female) declined for adults fed 1 soybean aphid nymph daily. The intrinsic rate of increase of O. insidiosus ranged from 0.048 to 0.133. Compared to other prey species, soybean aphid is an adequate prey item for O. insidiosus. Our results suggest that O. insidiosus will be most effective in suppressing soybean aphid population growth in the initial phase of the aphid’s colonization of soybeans.