Search

The article focuses on the potential cost-effective use of Trichogramma parasitoids in managing Spodoptera pests, particularly the fall armyworm, which poses a significant threat to global food security. Topics include the protective scale variation on Spodoptera egg masses, the non-renewable nature of these scales, and the performance of Trichogramma species based on different egg scale thicknesses, challenging previous conclusions about their effectiveness as parasitoids.

Autoparasitoids are important biocontrol agents for controlling hemipteran pests. Females of these wasps lay fertilized eggs in whitefly nymphs (primary host) which develop as females. The males develop as hyperparasitoids from unfertilized eggs on conspecific or other primary parasitoid species (as secondary hosts). To date, the effects of mating and secondary host sex on hyperparasitism have been largely neglected. We studied heteronomous hyperparasitism of mated and unmated Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) females on different secondary hosts (conspecific or heterospecific: Eretmocerus hayati Zolnerowich & Rose (Hymenoptera: Aphelinidae)) in no-choice and paired-choice bioassays. We demonstrated that regardless of their mating status E. sophia females were unable to parasitize male secondary hosts. Although mating of E. sophia females had no effect on the number of parasitized conspecific females, the number of heterospecific females (E. hayati) parasitized by mated E. sophia was greater than in the unmated females. The mating status of E. sophia females had no effect on host feeding on conspecific secondary hosts, but it did increase host feeding on heterospecific secondary hosts (E. hayati). In no-choice bioassays, both mated and unmated E. sophia females preferred E. sophia third instar female larvae and one-day-old E. hayati female pupae as their hosts, and preferred to feed on E. sophia third instar female larvae. In paired-choice bioassays, E. sophia females preferred to feed on E. hayati male pupae over female pupae, and consumed more E. sophia female pupae than male pupae regardless of mating status. Our results suggest that mating status modulates parasitism and host feeding of E. sophia females on heterospecific secondary hosts. In addition, we demonstrated that E. sophia females are unable to parasitize secondary male hosts to produce E. sophia males. [ABSTRACT FROM AUTHOR]

The egg parasitoid Trichogramma dendrolimi Matsumura is one of the most widely used agents in sustainable crop protection to manage many lepidopteran pests in China, especially via inundative releases. It has been used as an important biocontrol agent in Integrated Pest Management (IPM) programs for the control of the plum fruit moth Grapholitha funebrana Tr. However, accurate knowledge of the parasitoid's biology and ecology is needed to optimize its practical application in pest management. In the current study, the effect of key factors on T. dendrolimi effectiveness as biocontrol agent, including host age, exposure time, parasitoid density and, host density was evaluated under laboratory conditions. The parasitoid showed a higher parasitism rate on younger over older G. funebrana eggs. When host egg density increased, the number of eggs parasitized by the parasitoid also increased, but parasitism rates decreased. The functional response of T. dendrolimi on G. funebrana eggs fitted the Holling type II Model (Nt = 0.932N/(1+0.112N)). When parasitoid density and exposure time of hosts to parasitoids increased, the parasitism rate of T. dendrolimi also increased. In addition, previous exposure of host eggs to ultraviolet (UV) light did not affect parasitism rate. All aforementioned factors did not influence the emergence rate of the parasitoid offspring. Our results would provide references for optimizing the application of T. dendrolimi inundative releases in large-scale management of G. funebrana in orchards. [ABSTRACT FROM AUTHOR]

The preference of Trichogramma parasitoids is known to be modulated by the fertilization status of host eggs encountered. However whether the actual suitability of host eggs is at play for modulating the preference of Trichogramma when choosing fertilized vs. unfertilized host eggs has not been well documented yet. In the present study, fertilized and unfertilized eggs of Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae), of which the eggs are suitable for Trichogramma ostriniae (Pang & Chen) (Hymenoptera: Trichogrammatidae) but are suboptimal for T. dendrolimi Matsumura, were used to investigate host preference, host acceptance, and offspring performance of the two Trichogramma species. The results showed that, in a no-choice test, T. dendrolimi parasitized significantly more unfertilized O. furnacalis eggs than fertilized ones. In contrast, the number of fertilized eggs parasitized by T ostriniae was significantly higher than for unfertilized eggs. The sex ratio (female proportion), developmental time and fitness of offspring wasps were similar between fertilized and unfertilized host eggs for both Trichogramma species. In a choice test, T. dendrolimi preferred unfertilized host eggs over fertilized ones, whereas T. ostriniae did not show a preference. The higher rate of eggs laying by T. dendrolimi on unfertilized eggs than on fertilized ones may explain the different parasitism performances reported for the two Trichogramma species. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Applied Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Population genetic structuring is common among herbivorous insects and frequently is associated with divergent host plants, such as crops and their wild relatives. Previous studies showed population genetic structuring in corn leafhopper Dalbulus maidis in Mexico, such that the species consists of two sympatric, host plant‐associated populations: an abundant and widespread "pestiferous" population on maize (Zea mays mays), and a small and localized "wild" population on perennial teosinte (Zea diploperennis), a maize wild relative with a limited distribution. This study addressed whether assortative mating and immigrant inviability mediate genetic structuring of corn leafhopper by comparing the mating and reproductive successes of pestiferous and wild females that colonize their nonassociated host plants against the successes of females colonizing their associated host plants. Assortative mating was assessed by comparing mating frequencies and premating and mating times among females of each population on each host plant; immigrant inviability was assessed by comparing, across two generations, the fecundity, survival, development time, sex ratio, and population growth rate among leafhopper populations and host plants. Our results showed that on maize, and compared to resident, pestiferous females, wild females were more likely to mate, and greater proportions of their offspring survived to adult stage and were daughters; consequently, the per‐generation population growth rate on maize was greater for immigrant, wild leafhoppers compared to resident, pestiferous leafhoppers. Our results suggested that wild leafhoppers emigrating to maize have a fitness advantage over resident, pestiferous leafhoppers, while immigrant pestiferous and resident wild leafhoppers on teosinte have similar fitnesses. [ABSTRACT FROM AUTHOR]

Lateralization is a fundamental principle of the brain organization widespread among vertebrates but rather unknown in invertebrates. Evidences of lateralized courtship and mating behavioral traits in parasitic wasps are extremely rare. Here, courtship and mating sequences and the presence of mating lateralization in Anagyrus sp. near pseudococci, one of the most effective biological control agents of mealybugs, were investigated. Courtship and mating behavior in A. sp. near pseudococci consisted in the male chasing of the female, pre-copula, copula, and post-copula phases. Males mating success was not related to the duration of chasing and pre-copula. High-speed videos showed population-level lateralization in A. sp. near pseudococci during courtship. Most the wasps used the right antenna to start antennal tapping and this led to a higher mating success, although lateralization had no impact on the frequency of the antennal tapping. Both females and males displayed this behavior. Higher mating success was detected when females displayed antennal tapping during sexual interaction, though male tapping was performed with a slightly higher frequency. To the best of our knowledge, this report on behavioral asymmetries of mating traits in A. sp. near pseudococci represents a quite rare evidence of lateralized behavior in parasitic wasps of economic importance. Our findings add basic knowledge on the behavioral ecology of this biocontrol agent with potential implications on the optimization of mass-rearing procedures aimed at using this parasitoid in Integrated Pest Management. [ABSTRACT FROM AUTHOR]

BACKGROUND Geocoris punctipes (Hemiptera: Lygaeidae) and Eretmocerus eremicus (Hymenoptera: Aphelinidae) are whitefly natural enemies. Previously, under laboratory conditions, we showed that G. punctipes engages in intraguild predation ( IGP), the attack of one natural enemy by another, on E. eremicus. However, it is unknown whether this IGP interaction takes place under more complex scenarios, such as semi-field conditions. Even more importantly, the effect of this interaction on the density of the prey population requires investigation. Therefore, the present study aimed to establish whether this IGP takes place under semi-field conditions and to determine whether the predation rate of G. punctipes on the whitefly decreases when IGP takes place. RESULTS Molecular analysis showed that, under semi-field conditions, G. punctipes performed IGP on E. eremicus. However, although IGP did take place, the predation rate by G. punctipes on the whitefly was nevertheless higher when both natural enemies were present together than when the predator was present alone. CONCLUSION While IGP of G. punctipes on E. eremicus does occur under semi-field conditions, it does not adversely affect whitefly control. The concomitant use of these two natural enemies seems a valid option for inundative biological control programmes of T. vaporariorum in tomato. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Intraguild predation ( IGP), predation between species that use a common resource, can affect the populations of a pest, of the pest's natural enemy ( IG prey) and of the predator of the pest's natural enemy ( IG predator). In this study, we determined whether the parasitoid Eretmocerus eremicus (Hymenoptera: Aphelinidae) ( IG prey), modifies its foraging behaviour under the risk of IGP by Macrolophus pygmaeus (Hemiptera: Miridae) ( IG predator). Parasitoid behaviour was analysed using two bioassays (choice and no-choice) with the following treatments: (i) control, tomato leaf infested with whitefly nymphs; and (ii) PEP, tomato leaf infested with whitefly nymphs and previously exposed to the IG predator; and (iii) PP, tomato leaf infested with whitefly nymphs, with both, the IG predator and the IG prey present. RESULTS In both bioassays, we found that E. eremicus did not significantly modify the number of ovipositions, time of residence, duration of oviposition or behavioural sequence. However, in the no-choice bioassay, the number of attacks was higher and their duration shorter in the PEP treatment than in the control. CONCLUSION Our results indicate that the parasitoid may detect IGP risk to a certain extent, but it did not significantly modify its foraging behaviour, suggesting that simultaneous release of the two natural enemies can be successfully employed. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Intraguild predation (IGP) takes place when natural enemies that use similar resources attack each other. The impact of IGP on biological control can be significant if the survival of natural enemy species is disrupted. In the present study, we assessed whether Geocoris punctipes (Hemiptera: Lygaeidae) engages in IGP on Eretmocerus eremicus (Hymenoptera: Aphelinidae) while developing on whitefly nymphs of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). In choice and non-choice tests, we exposed G. punctipes to parasitized and non-parasitized whitefly nymphs. We found that G. punctipes does practice IGP on E. eremicus. However, choice tests assessing G. punctipes consumption revealed a significant preference for non-parasitized T. vaporariorum nymphs. Subsequently, we investigated whether E. eremicus females modify their foraging behavior when exposed to conditions involving IGP risk. To assess this, we analyzed wasp foraging behavior under the following treatments: i) whitefly nymphs only (control = C), ii) whitefly nymphs previously exposed to a predator ( = PEP) and, iii) whitefly nymphs and presence of a predator ( = PP). In non-choice tests we found that E. eremicus did not significantly modify its number of attacks, attack duration, oviposition duration, or behavior sequences. However, E. eremicus oviposited significantly more eggs in the PEP treatment. In the PP treatment, G. punctipes also preyed upon adult E. eremicus wasps, significantly reducing their number of ovipositions and residence time. When the wasps were studied under choice tests, in which they were exposed simultaneously to all three treatments, the number of attacks and frequency of selection were similar under all treatments. These results indicate that under IGP risk, E. eremicus maintains several behavioral traits, but can also increase its number of ovipositions in the presence of IG-predator cues. We discuss these findings in the context of population dynamics and biological control. [ABSTRACT FROM AUTHOR]