Non-target effects of ten essential oils on the egg-parasitoid Trichogramma evanescens

Essential oils (EOs) are increasingly used as biopesticides due to their insecticidal potential. This study addresses their non-target effects on a biological control agent: the egg parasitoid Trichogramma evanescens. In particular, we tested whether EOs affected parasitoid fitness either directly, by decreasing pre-imaginal survival, or indirectly, by disrupting parasitoids' orientation abilities. The effect of Anise, Fennel, Sweet orange, Basil, Coriander, Oregano, Peppermint, Mugwort, Rosemary and Thyme EOs were studied on five strains of T. evanescens. Specific experimental setups were developed, and data obtained from image analysis were interpreted with phenomenological models fitted with Bayesian inference. Results highlight the fumigant toxicity of EOs on parasitoid development. Anise, Fennel, Basil, Coriander, Oregano, Peppermint and Thyme EOs are particularly toxic and drastically reduce the emergence rate of T. evanescens. Most EOs also affect parasitoid behavior: (i) Basil, Coriander, Oregano, Peppermint, Mugwort and Thyme EOs are highly repellent for naive female parasitoids; (ii) Anise and Fennel EOs can have repellent to attractive effects depending on strains; and (iii) Sweet orange, Oregano and Rosemary EOs have no detectable impact on orientation behavior. This study shows that EOs fumigation have non-target effects on egg parasitoids. This highlights the need to cautiously precise the deployment framework of biopesticides in an agroecological perspective.

Old Parasitoids for New Mealybugs: Host Location Behavior and Parasitization Efficacy of Anagyrus vladimiri on Pseudococcus comstocki

The Comstock mealybug, Pseudococcus comstocki (Hemiptera: Pseudococcidae) is a primary pest of orchards in the North and Northwest of China. This pest appeared recently in Europe, including Italy, where it is infesting mainly vineyards as well as apple and pear orchards. The present study investigated the efficacy of Anagyrus vladimiri, a known biological control agent (BCA) of Planococcus ficus, on P. comstocki to evaluate a potential use for the management of this new pest. No-choice tests were conducted to quantify the parasitoid behavior against P. ficus and P. comstocki. The parasitoid successfully parasitized both species (parasitization rate: 51% and 67% on P. comstocki and P. ficus, respectively). The A.vladimiri developmental time (19.67 ± 1.12 vs. 19.70 ± 1.07 days), sex ratio (1.16 ± 1.12 vs. 1.58 ± 1.07) and hind tibia length of the progeny showed no differences when P. comstocki and P. ficus, respectively, were exploited as hosts. Two-choice tests, conducted by providing the parasitoid with a mixed population of P. ficus and P. comstocki, showed no host preference for either of the two mealybug species (23 vs. 27 first choices on P. comstocki and P. ficus, respectively). The parasitization rate (61.5% and 64.5% in P. comstocki and P. ficus, respectively) did not differ between the two hosts. Overall, our study adds basic knowledge on parasitoid behavior and host preferences and confirms the use of this economically important encyrtid species as an effective BCA against the invasive Comstock mealybug.

Primeiro registro da vespa parasitoide Pachysomoides, associada a ninhos de Mischocyttarus cerberus e alguns comentários sobre o comportamento da espécie de vespa parasitoide

In this work, we are reporting, for the first time, a parasitoid wasp associated to the nests of Mischocyttarus cerberus, also we provide information concerning the parasitoid behavior when close to its host. We believe that the parasitism process is not easily accomplished, because the host resident females keep guarding and attacking whenever they detect any kind of parasitoid approach. Our results provide more detailed and important information about the host-parasitoid interaction behavior involving the Pachysomoides sp. and M. cerberus, which so far is scarce scientific literature.

Studi keberadaan hiperparasitoid dalam mempengaruhi perilaku imago parasitoid pada kutudaun, Aphis gossypii (Hemiptera: Aphididae)

Study Hyperparasitoid Existing Affected to Adul Parasitoid Behavior on Aphid, Aphis gossypii (Hemiptera: Aphididae). In general, hyperparasitoid is needed for establishing food and chain webs, but in contrary, it could become a limiting factor in existing biological control program. An observation to aim positive impact of hyperparasitoid existence has been carried out. Chili plant, Capsicum annuum, Aphis gossypii, Trioxys sinensis parasitoid and Aphidencyrtus sp. were used in this observation. Results showed that hyperparasitoid existence assisted parasitoid distribution. Parasitoids were placed with hyperparasitoids enhanced parasitoid distribution or dispersion two times farther compare to without hyperparasitoids. It was concluded that dispersal behaviour of hyperparasitoid adult was a parasitoid adult’s response to avoid its suppression by the hyperparasitoid and also increase parasitoid’s searching ability.

From parasitoid behavior to biological control: applied behavioral ecology

A hypothetical parasitoid mass rearing facility is used to unite principles from behavioral ecology and biological control. The key to the problem is variation in the tendency of solitary parasitoids to superparasitize. Superparasitism affects individual and population parasitoid productivity, though not necessarily to the same degree. Herein, the interest is in determining conditions that will maximize parasitoid population productivity when superparasitism varies. To accomplish this, a combination of graphical marginal analysis (to provide an economic context), dynamic optimization models (to determine individual parasitoid superparasitism tendency), and functional response models (to determine parasitoid population productivity) has been used. Marginal analysis shows that marginal returns decrease with an increase in the number of parasitoids released but that the slope of the marginal returns curve depends upon the sensitivity of superparasitism to environmental conditions. In addition, results show that parasitoid responses can be highly nonlinear and, as such, can greatly affect optimal numbers of parasitoids released in a nonintuitive manner. This behavioral ecology approach greatly increases efficiency and predictability of parasitoid production.