Mummy Production Research Articles

Effects of Plant Stress on Aphid-Parasitoid Interactions: Drought Improves Aphid Suppression.

Drought events have the potential to mediate tri-trophic interactions. Changes in plant quality influence herbivore performance, which affects prey availability and quality for natural enemies. Parasitoid wasps are particularly vulnerable to these changes since their development is inextricably linked to that of their prey. However, we know little about the indirect effects of plant water limitation on parasitoid performance, especially the consequences of mild water limitation. This study investigated the ability of a parasitoid wasp (Aphidius colemani Viereck (Hymenoptera: Braconidae)) to suppress aphid (Rhopalosiphum padi L. (Hemiptera: Aphididae)) populations on well-watered, mildly stressed, or highly stressed wheat (Triticum aestivum L. (Poales: Poaceae)). We then investigated the role that aphid body size and behavioral interactions might play in wasp acceptance of aphid hosts. We found improved aphid suppression under mild and high-water limitation, but the underlying mechanisms were different. Mild-stress appeared to maximize parasitoid performance, as indicated by the highest mummy production. Aphids were larger when feeding on mildly stressed plants than on any other treatment, which suggests improved aphid quality for parasitoids. Improved aphid suppression under high-stress may have been driven by enhanced nonconsumptive effects. Despite improved aphid suppression, mummy formation was lowest on highly stressed plants. High-stress conditions have been shown to negatively affect aphid performance, so improved aphid suppression may be driven by poor aphid performance exacerbating the cost of interactions with parasitoids, such as stinging. No differences were observed in parasitoid foraging behaviors such as antennation or stinging across any treatments. This study highlights the importance of plant water stress intensity in affecting outcomes of parasitoid-host interactions.

Timing alters how a heat shock affects a host-parasitoid interaction.

Abiotic factors' effects on species are now well-studied, yet they are still often difficult to predict, especially for strongly interacting species. If these altered abiotic factors and species interactions occur as discrete events in time, such complications may occur because of the events' relative timing. One such discrete abiotic factor is the short-duration, large magnitude increase in temperature called a heat shock. This study investigates how the timing of heat shocks affects the successful attack and reproduction of a parasitoid wasp (Aphidius ervi) attacking its host, the pea aphid (Acyrthosiphon pisum). We tested three relative timings: 1) heat shock before the wasp attacks hosts, 2) heat shock while the wasp is foraging, and 3) heat shock after the wasp has attacked hosts. In each scenario we compared wasp mummy production (pupal stage) with and without a heat shock. Our results showed that a heat shock had the largest effect when it occurred while wasps actively foraged, with fewer mummies produced when exposed to a heat shock compared to the no heat shock control. Follow-up behavioral tests suggest this was caused by wasps becoming inactive during heat shocks. In contrast, when heat shocks were applied three days before or after foraging, we found no difference in mummy production between the heat shock treatment and no heat shock control. These results show the potential importance of timing when considering the ramifications of an altered abiotic factor, especially with relatively discrete abiotic events and interactions.

The influence of feeding and host deprivation on egg load and reproduction of an aphid parasitoid, Aphidius gifuensis (Hymenoptera: Braconidae)

With a view to improving the establishment of Aphidius gifuensis Ashmead, a potential natural enemy for suppression of aphids on vegetables, the effects of host deprivation and honey feeding before release on the parasitoid’s egg load and reproduction were studied under laboratory conditions. Host deprivation significantly affected mummy production and survival rate of female parasitoids. A. gifuensis produced more mummies when exposed to a short period (1 and 2 days) of host deprivation, but when host deprivation lasted for 3 days, their mummy production sharply decreased. Offspring produced by parasitoids that had been deprived of hosts for 2 days were much heavier than those produced by parasitoids deprived of hosts for 1 and 3 days. However, host deprivation did not affect emergence rate or offspring sex ratio; the emergence rate was always above 80%, and the offspring sex ratio was always female biased irrespective of whether the host-deprivation period was 1, 2, or 3 days. Honey feeding greatly increased egg load, longevity and decelerated oosorption of A. gifuensis when hosts were absent, and significantly increased parasitoid mummy production in late age. We discuss the results in the context of augmentative biological control, with the view to understanding how to increase parasitoid performance after they are released.

Protection of Pea Aphids Associated with Coinfecting Bacterial Symbionts Persists During Superparasitism by a Braconid Wasp.

Bacterial endosymbionts that associate facultatively with insect herbivores can influence insect fitness and trophic interactions. The pea aphid, Acyrthosiphon pisum, can be protected from parasitism by the braconid wasp Aphidius ervi when harbouring particular symbiotic bacteria, with specific endosymbiont coinfections providing almost complete protection. However, studies often quantify aphid mummification with no control over parasitoid oviposition per aphid; thus, if mummy production fails or is low, the causes are often unclear. Here, we show that the high level of protection associated with the coinfecting endosymbionts Hamiltonella defensa and X-type is maintained even when pea aphids are superparasitised. This contrasts strongly with the protection provided by H. defensa alone, which has been shown by others to be overcome by superparasitism. By dissecting aphids exposed to two parasitoid attacks, we reveal that A. ervi deposits eggs equally freely in endosymbiont-infected and uninfected nymphs, and lack of mummification in endosymbiont-protected nymphs arises from failure of the wasp eggs to hatch or emerging larvae to develop.

Influence of Temperature on Flight, Walking and Oviposition Capacities of two Aphid Parasitoid Species (Hymenoptera: Aphidiinae)

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is one of the major pests of many greenhouse crops. The aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday) (Hymenoptera: Braconidae: Aphidiinae) have been considered good agents for the biological control of A. gossypii. In Mediterranean area, these parasitoids can currently be released under elevated temperature conditions. However, few findings on their behavior changes with temperature are available. In this study, we analyze the consequence of constant temperatures ranging from 20 to 32 °C on the flight, walking and oviposition capacities of Aphidius colemani and Aphidius matricariae. Our results revealed that flight capacity is clearly influenced by temperature. The optimal temperatures for flying are 20 and 25 °C for A. colemani and A. matricariae, respectively. For both species, we observed an increase in the walking capacity but a decrease in the reproductive potential at higher temperatures. Furthermore, regardless of the tested temperature, the mummy production rate was always higher in A. colemani than in A. matricariae. These results indicate that A. colemani is more suitable than A. matricariae for the biological control of A. gossypii in Mediterranean environments. © 2015, Springer Science+Business Media New York.

Suitability of three aphid species for Aphidius gifuensis (Hymenoptera: Braconidae): Parasitoid performance varies with hosts of origin

Oviposition behavior and offspring fitness of the parasitoid Aphidius gifuensis (Ashmead) were compared on three aphid species, Sitobion avenae F., Myzus persicae (Sulzer), and Aphis gossypii Glover using wasps collected from both S. avenae and M. persicae. A. gifuensis produced more mummies and adults on S. avenae and M. persicae than on A. gossypii regardless of the host of origin. Mummy production was influenced by attack rate and percentage of aphids superparasitized. The F1 generations from S. avenae and M. persicae were more female-biased and wasps were larger than those from A. gossypii. Although there were significant differences in development time of A. gifuensis in the three aphid species, the difference was generally shorter than one day. Fewer mummies were produced when A. gifuensis was transferred between S. avenae and M. persicae, but no significant difference was observed in emergence rate, percentage of female offspring, or body size. The effects of host species on A. gifuensis female performance and offspring fitness are discussed, along with the potential for using A. gifuensis to control M. persicae and A. gossypii.

Factors Contributing to the Poor Performance of a Soybean Aphid Parasitoid <I>Binodoxys communis</I> (Hymenoptera: Braconidae) on an Herbivore Resistant Soybean Cultivar

Host plant resistance and biological control are important components of integrated pest management programs. However, plants expressing resistance to herbivores may also have direct or indirect negative effects on natural enemies simultaneously providing pest suppression. Soybean aphids (Aphis glycines Matsumura) are invasive and serious pests of soybean (Glycine max L.) in the United States. Several soybean lines with aphid resistance have been identified, but the long-term impact of these resistant plants on soybean aphid biological control agents is uncertain. In a previous study, we reported that a soybean aphid parasitoid, Binodoxys communis (Gahan) had lower mummy production on resistant plants compared with a near isogenic susceptible soybean line, but the reason for this was unclear. Therefore, we examined three possible mechanisms to explain these findings: 1) resistant plants directly impact wasp emergence and longevity, 2) varying aphid density influences parasitism rates, and 3) resistant plants indirectly affect wasp development through reduced aphid longevity. We found that parasitoids in this study were not directly influenced by resistant cultivars, as there was no difference in wasp adult emergence or longevity between resistant and susceptible plants. There was also no significant effect of aphid density on mummy production over the range of aphid densities we tested. However, aphids on resistant plants had significantly shorter lifespans and were unable to survive long enough to develop into mummies compared with aphids on susceptible plants. We discuss these results and possible implications for integrating biological control and host plant resistance within soybean aphid integrated pest management programs.

Life history characteristics of Aphidius transcaspicus, a parasitoid of mealy aphids ( Hyalopterus species)

Aphidius transcaspicus Telenga (Hymenoptera: Braconidae: Aphidiinae) is a solitary koinobiont endoparasitoid that has been selected for use as a biological control agent against the mealy plum aphid Hyalopterus pruni (Geoffroy) (Hemiptera: Aphididae) in prune orchards in California. Using the alternative host Aphis fabae Scopoli (Hemiptera: Aphididae) on the host plant Vicia faba L., we determined the adult longevity and fecundity, and progeny development time and sex ratio of A. transcaspicus. Mated female parasitoids were given new, individually-enclosed, host-infested bean plants each day of her adult life. Mummified hosts were monitored daily for adult progeny emergence. Adult lifespan of parent females averaged 6.67 ± 0.56 days, and mean lifetime mummy production was 196.1 ± 19.9 per female. There was a significant linear relationship between total mummy production and both adult female weight at eclosion and adult female longevity. Mean development time of progeny was 13.3 ± 0.1 days, and varied significantly with sex and parent female age. Overall, 74% of parasitoid mummies survived to adult eclosion, but survival decreased with parent age. Lifetime sex ratio was 0.53 female, and sex ratios declined with female age. The intrinsic rate of natural increase was estimated to be 0.21, with net reproductive rate of 31.10, and mean generation time of 16.35 days.

TOOLS FOR EVALUATING LIPOLEXIS OREGMAE (HYMENOPTERA: APHIDIIDAE) IN THE FIELD: EFFECTS OF HOST APHID AND HOST PLANT ON MUMMY LOCATION AND COLOR PLUS IMPROVED METHODS FOR OBTAINING ADULTS

Abstract Lipolexis oregmae Gahan was introduced into Florida in a classical biological control program directed against the brown citrus aphid, Toxoptera citricida (Kirkaldy), on citrus. Prior to evaluating distribution, host range, and potential nontarget effects of L. oregmae in Florida, we evaluated the role of other potential host aphids and host plants on mummy production and location. Under laboratory conditions, this parasitoid produced the most progeny on the target pest, the brown citrus aphid on citrus. This parasitoid, unlike the majority of aphidiids, did not produce mummies on any of the host plants tested when reared in black citrus aphid T. aurantii (Boyer de Fonscolombe) on grapefruit, spirea aphid Aphis spiraecola Patch on grapefruit and pittosporum, cowpea aphid A. craccivora Koch on grapefruit and cowpeas, or melon aphid A. gossypii Glover on grapefruit and cucumber. Thus, sampling for L. oregmae mummies of these host aphids and host plants must involve holding foliage in the laboratory...

Age-specific survival and fecundity and their effects on the intrinsic rate of increase of Aphelinus gossypii (Hym., Aphelinidae), a parasitoid of Aphis gossypii (Hom., Aphididae)

Abstract: The age-specific survival and fecundity of female adults of the aphidophagous parasitoid, Aphelinus gossypii Timberlake (Hym., Aphelinidae), were determined at a host density of 50 Aphis gossypii Glover (Hom., Aphididae) per leaf of Ageratum houstonianum Mill each day at 25°C. The age-specific mummy production, emergence rate and sex ratio of progeny were calculated. The implication of these results in terms of potential population growth of A. gossypii and related species is discussed. The age-specific survival curve (lx) of females exhibited a Type I pattern, which resulted in little difference between Σmx and Σlx mx. The lx curve of males exhibited a Type II pattern, and their survival time was much shorter than that of females. Each mated female produced on average 598.9 ± 64.0 aphid mummies, and preyed on 87.9±6.2 aphids. Most of the biological performance parameters were not different significantly between mated and virgin females. The highly female-biased sex ratio of offspring produced by mated females soon after their emergence resulted in a high fecundity rate (mx) during the early reproductive period. Therefore, although the sex ratio of progeny was male-biased during the entire reproductive period, the intrinsic rate of increase estimated using age-specific sex ratios was larger than that estimated using a constant sex ratio of 0.5. These results indicate that the high survival and the adaptation of producing mostly female offspring during the early reproductive period contribute much to the population increase potential of this parasitoid.

Sub-lethal Effects of the Insecticides Pirimicarb and Dimethoate on the Aphid Parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) When Attacking and Developing in Insecticide-Resistant Hosts

The effectiveness of parasitoids as biological control agents can be constrained by insecticide use, not only through direct mortality but also as a result of sublethal effects. Several pest aphids have become resistant to a range of insecticides and a resistant strain of Myzus persicae was used in laboratory experiments to investigate sublethal effects of the insecticides pirimicarb and dimethoate on the parasitoid Diaeretiella rapae . Both insecticides produced sublethal effects on D. rapae when the parasitoid attacked and developed in aphids that had been dipped in insecticide solutions. Dimethoate affected oviposition behaviour; females were apparently repelled by residues on the surface of dipped aphids, thus reducing their attack rate and hence the number of mummies produced. Also, the reproductive performance of parasitoids that had developed in pirimicarb-dipped aphids appeared to be adversely affected, in comparison with parasitoids that emerged from uncontaminated hosts, and this was reflected both in lower mummy production and lower attack rates. Pirimicarb, but not dimethoate, affected the sex ratio of the offspring of D. rapae that had developed in dipped aphids, causing a significant increase in the proportion of males. This only occurred when the male parent had developed in a pirimicarb-dipped aphid, suggesting that the effect involves male sterility or mating behaviour, although they appeared to mate normally. These sublethal effects are potential constraints on the efficiency and effectiveness of D. rapae as a biological control agent of aphid pests, but to assess fully their potential impact further studies need to be done using more realistic extended laboratory and semi-field techniques.

Colonization behaviour and parasitization by Ephedrus cerasicola (Hym., Aphidiidae) in choice studies with two species of plants and aphids

AbstractExperienced females of the aphid parasitoid Ephedrus cerasicola Stary were released into a glasshouse compartment or into a cage, where they could choose between an equal number of cucumber and swede plants. The plants were uninfested in some experiments, or cucumbers were infested with Aphis gossypii Glover and swedes with Myzus persicae (Sulzer). The parasitoids were reared on M. persicae on swedes. In all experiments, both with uninfested and infested plants, the females colonized the cucumber plants much more frequently than the swedes. Also mummy production was higher on the cucumber plants.In some additional cage experiments with a single infested plant (no choice), A. gossypii on cucumbers were more parasitized than M. persicae on swedes in three of four experiments.The results indicate that even if E. cerasicola is reared on M. persicae/swedes, parasitoid females released into a cucumber glasshouse will probably readily spread to the cucumber plants and parasitize A. gossypii there.

The abilities of the aphid parasitoids Aphidius ervi Haliday and A. rhopalosiphi De Stefani Perez (Hymenoptera: Braconidae) to transfer between different known host species and the implications for the use of alternative hosts in pest control strategies

AbstractA series of host-transfer trials using both laboratory-cultured and field-collected individuals of the aphid parasitoids Aphidius ervi Haliday and A. rhopalosiphi De Stefani Perez were done in order to clarify inconsistent results from several previous studies. A. ervi cultured on Acyrthosiphon pisum (Harris) produced very few mummies when confined with Microlophium carnosum (Buckton), whereas those cultured on M. carnosum produced as many mummies on A. pisum as they did on their original host. Mummy production was correlated with the attack rate of adult parasitoids on potential hosts. The production of mummies on M. carnosum by parasitoids reared on A. pisum was often greatly improved if their male parent had been reared on M. carnosum, suggesting that genotype strongly influences host preference. Aphidius rhopalosiphi from laboratory cultures produced significantly more mummies on Metopolophium dirhodum (Walker) than on Sitobion avenae (F.) regardless of their original host, but this preference was not shown by parasitoids from field populations. It is concluded that inadvertent selection occurs in laboratory cultures of aphid parasitoids as a result of low founder numbers, genetic drift and genetic bottlenecks and that this can strongly influence experimental results in biology and behaviour studies, which has important implications for biological control workers.