Xanthomonas arboricola pv. juglandis (hereafter X. juglandis) is the etiological agent of walnut blight, the most important bacterial disease affecting walnut production worldwide. Currently, the disease is treated mainly with copper-derived compounds (e.g., CuSO4) despite the evidence of genetic resistance in these strains. Regarding the effectiveness and sustainability, the use of a bacteriophage appears to be a biocontrol alternative to reduce X. juglandis load and symptomatology of walnut blight. Here, the phages f20-Xaj, f29-Xaj, and f30-Xaj were characterized, and their effectiveness in walnut orchards against walnut blight was determined. These bacteriophages showed a specific lytic infection in X. juglandis strains isolated from Chile and France. Phylogenetic analysis of the complete genome of f20-Xaj and f30-Xaj indicates that these phages belong to the Pradovirus genus. In the field, the cocktail of these bacteriophages showed similar effectivity to CuSO4 in the reduction of incidence and severity in walnut tissue. Moreover, the bacterial load of X. juglandis was significantly reduced in the presence of bacteriophages in contrast to a CuSO4 treatment. These results show that the use of bacteriophages can be an alternative to combat the symptoms of walnut blight caused by X. juglandis.

We examined whether Macrocentrus cingulum (Hymenoptera: Braconidae) of Asian origin could serve as a biological control agent of the maize pest Ostrinia nubilalis (Lepidoptera: Crambidae) in Europe. M. cingulum is already present in Europe, where it does not parasitize O. nubilalis but Ostrinia scapulalis, a related species feeding on wild dicotyledons. In contrast, M. cingulum have been imported from Europe and Asia into North America (where O. nubilalis had been accidentally introduced from Europe), and does parasitize O. nubilalis there. We conducted laboratory infestations to assess host acceptability (parasitoid's propensity to oviposit) and suitability (parasitoid's ability to develop) of European O. nubilalis for M. cingulum of European and Asian origin, and of Ostrinia furnacalis (their original host) for Asian M. cingulum. Asian M. cingulum parasitized European O. nubilalis as readily as O. furnacalis, and developed equally well in terms of: % female cocoons, time to first emergence from the cocoon, total number of adult offspring, % female offspring and adult longevity. Adult female parasitoids were significantly larger when emerging from O. nubilalis, mixed-sex and male cocoons were significantly more and less frequent, respectively. The acceptability of O. nubilalis was significantly lower for European than for Asian M. cingulum, and its suitability was zero. Asian M. cingulum appears a potential candidate for introduction as a biological control agent of a major maize pest, European 0. nubilalis, provided environmental impact studies, economic analyses, and foreseeable interactions with other biological control agents such as the egg parasitoid Trichogramma brassicae (Hymenoptera: Trichogrammatidae) are satisfying. (C) 2014 Elsevier Inc. All rights reserved.

Two cornborer species, Ostrinia furnacalis (Lepidoptera: Crambidae) and O. nubilalis, are major corn pests in Asia and Europe, respectively. In both continents, the larval endoparasitoid Macrocentrus cingulum (Hymenoptera: Braconidae) develops on another, closely related stemborer, O. scapulalis, which feeds on mugwort and other dicotyledons. M. cingulum also emerges from O. furnacalis in Asia and O. nubilalis in North America, but not from O. nubilalis in Europe. We assessed the ability of three populations of each of the three Ostrinia species to encapsulate foreign bodies of a size similar to that of a M. cingulum egg. We conclude that variations in encapsulation ability alone cannot account for the differences observed in the field between parasite emergence rates in these different host species and geographic areas.

In parasitoids, host-habitat odour can influence host searching within the habitat. This is the case in Leptopilina sp. (Hymenoptera, Figitidae), a Drosophila parasitoid searching for larvae by ovipositor probes. This a behaviour can be conditioned to fruit odours. In a previous study, the latency of probing to a fruit odour is reported to have a genetic variability within a laboratory strain. This suggests a link between rapidity of host discovery and fitness. In the present study, this hypothesis is tested by comparing responses to host-habitat odours between two genotypes of Leptopilina heterotoma Thomson, from the Mediterranean coast (Antibes) and from Burgundy (Tailly). The two genotypes present contrasting rhythms and levels, of locomotor activity linked to contrasting interspecific competition in their area of origin. The high activity observed in the Mediterranean genotype is interpreted as an adaptive response to it limited time-window to win against a competitor species absent in Burgundy. The present study finds differentiation in innate but not learnt responses to host-habitat odours. The more active genotype (Antibes) has a higher probability and a shorter latency of innate probing to the odours than the less active genotype (Tailly); Antibes females also find larvae and complete infestations more rapidly. Learning equalizes the probability and the latency of probing, to the odours in both strains, and increases the probing duration. Innate responses to host-habitat odours would allow time-limited insects to increase their reproductive rate, when host predictability is high in the habitat. Selection of faster innate responses to host and habitat cues without evolution of learnt responses indicates that the initial host discovery is more crucial to fitness than subsequent ones.

The effect of different bean varieties on the performance of the bruchid beetle Zabrotes subfasciatus Boheman (Coleoptera: Bruchidae), was determined by using wild and cultivated seeds of the genus Phaseolus. Results showed that the quality of the host plant affected the performance and the oviposition behavior of female beetles. Overall, bruchid performance was higher on cultivated seeds than on wild seeds. It was also found that the oviposition behavior and the performance of their offspring differed between females that originated from wild versus cultivated seeds. We also demonstrated the importance of a genetic component in bruchid performance: longevity, fecundity, larval development, adult size, and the sex ratio of the progeny varied according to their maternal lineage (‘familyrsquo;). For example, on the same host type, some females laid twice as many eggs as females from other ‘familiesrsquo;, and the sex ratio among the offspring correlated with that of their mother. Thus, the performance and behavior of Z. subfasciatus are not only affected by environmen tal factors such as the quality of the seeds on which they develop, but also have a genetic basis which can counterbalance a less suitable quality of the host plant. For a crop pest such as Z. subfasciatus, its ability to survive and adapt on host plants of differing quality may be an important attribute to consider for pest management.

Phytophagous insects are dependent of their host plant for their successful development. In the special case of bruchid beetles, the seed is the structure on which they will complete their larval development. Due to the development of agriculture, some plants species have been domesticated for their use as a food resource. In the case of domestication of the genus Phaseolus, it has been shown that seeds from cultivated varieties contain higher levels of proteins and minerals and provide a higher quality resource for insects that feed upon these plants (the phytophagous pests and their associated parasitoids). In this study, I investigated the effects of bean domestication on Zabrotes subfasciatus, one of the main pests of field crop and stored beans in Mexico and Central America. Through experimental manipulations and quantitative genetics experiments, I determined the importance of environmental and genetic variation in the performance of this bruchid. The results showed that the quality of the host plant mediated the performance and the oviposition behaviour of female beetles. Overall, performance of the bruchids was higher on cultivated seeds than on wild seeds. It was also found that whether a female originated from wild or from cultivated seeds affected her behaviour and the performance of her offspring. Females that originated from cultivated seeds were less willing to lay eggs on a novel host seed than females that originated from wild seeds. Thus, the performance and behaviour of Z. subfasciatus are not only affected by environmental factors such as, the quality of the seeds on which they develop, but also have a genetic basis.