Verified and potential pathogens of predatory mites (Acari: Phytoseiidae)

Several species of phytoseiid mites (Acari: Phytoseiidae), including species of the genera Amblyseius, Galendromus, Metaseiulus, Neoseiulus, Phytoseiulus and Typhlodromus, are currently reared for biological control of various crop pests and/or as model organisms for the study of predator¿prey interactions. Pathogen-free phytoseiid mites are important to obtain high efficacy in biological pest control and to get reliable data in mite research, as pathogens may affect the performance of their host or alter their reproduction and behaviour. Potential and verified pathogens have been reported for phytoseiid mites during the past 25 years. The present review provides an overview, including potential pathogens with unknown host effects (17 reports), endosymbiotic Wolbachia (seven reports), other bacteria (including Cardinium and Spiroplasma) (four reports), cases of unidentified diseases (three reports) and cases of verified pathogens (six reports). From the latter group four reports refer to Microsporidia, one to a fungus and one to a bacterium. Only five entities have been studied in detail, including Wolbachia infecting seven predatory mite species, other endosymbiotic bacteria infecting Metaseiulus (Galendromus, Typhlodromus) occidentalis (Nesbitt), the bacterium Acaricomes phytoseiuli infecting Phytoseiulus persimilis Athias-Henriot, the microsporidium Microsporidium phytoseiuli infecting P. persimilis and the microsporidium Oligosproridium occidentalis infecting M. occidentalis. In four cases (Wolbachia, A. phytoseiuli, M. phytoseiuli and O. occidentalis) an infection may be connected with fitness costs of the host. Moreover, infection is not always readily visible as no obvious gross symptoms are present. Monitoring of these entities on a routine and continuous basis should therefore get more attention, especially in commercial mass-production. Special attention should be paid to field-collected mites before introduction into the laboratory or mass rearing, and to mites that are exchanged among rearing facilities. However, at present general pathogen monitoring is not yet practical as effects of many entities are unknown. More research effort is needed concerning verified and potential pathogens of commercially reared arthropods and those used as model organisms in research

Factors influencing citrus fruit scarring caused by Pezothrips kellyanus

[EN] Kelly s citrus thrips (KCT) Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) is a recently recorded cosmopolitan citrus pest, causing fruit scarring that results in downgrading of fruit. Due to the detrimental effects caused on fruits by KCT, we wanted to study some of the factors influencing fruit scarring. Specifically, the objectives were: (1) to determine the fruit development stage when citrus fruits are damaged by KCT and the population structure of KCT during this period, (2) to study the influence of temperature on intensity of damage, and finally, (3) to identify alternative host plants. KCT populations on flowers and fruitlets and alternate plant hosts were sampled in four citrus orchards from 2008 to 2010. The percentage of damaged fruits was also recorded. The exotic vine Araujia sericifera (Apocynaceae) was recorded as a new host for KCT. Thrips scarring started to increase at 350 650 degree-days (DD) above 10.2 C, coinciding with a peak abundance of the second instar larval stages over all 3 years of the study. The maximum percentage of larval stages of KCT was observed in the 3 years at about 500 DD, a period which corresponds to the end of May or early June. Variation in the severity of fruit scarring appeared to be related to air temperature. Temperature likely affects the synchronisation between the peak in abundance of KCT larvae, and the period when fruitlets are susceptible to thrips damage. Temperature can also influence the survival and development of KCT populations in citrus and other host plants in the citrus agro-ecosystem.The authors thank Alejandro Tena for his valuable suggestions and two anonymous referees for their careful review and helpful comments. We also extend our thanks to the owners of the commercial orchards for giving us permission to use their citrus orchards. 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