Summary 
Pezothrips kellyanus is a newly emerged pest in citrus orchards. In the decade of the 1990 first fruit scarring was observed in New Zealand and Australia. Nowadays, P. kellyanus is considered an occasional pest in several countries of Africa, Asia and Europe. In Spain damage was first detected in 2007, in La Ribera region (Valencia). Their populations are related to citrus flowering. Recently developed small fruits are scarred when thrips feed on them. Subsequently, when fruit grows, fruit scarring becomes apparent, mainly as scars around the calyx. With the general aim of improving the management of the pest and to reduce the incidence of fruit scarring, we have studied the behavior of their population, the way of evaluating their abundance and their natural enemies. Due to it is a relatively newly emerged pest, two specific objectives of our study were to describe both immature and adult stages of P. kellyanus and to know the geographic spread and alternative host plants in the citrus orchards of the “País Valencià”. The study was carried out from 2008 to 2010 in a variable number of citrus orchards (4-14) located in La Ribera region. The methodologies used were chosen in accordance with the objectives. 
Thrips species that coexist with P. kellyanus in the canopy and on the ground of the citrus orchards studied have been identified. Simultaneously with its spread in the Valencian region, Pezothrips kellyanus has displaced other thrips species abundant in the past in citrus orchards as Frankliniella occidentallis, Thrips tabaci and Thrips major. Those thrips species are not damaging citrus fruits. A key is provided in order to recognize the thrips pest species in citrus orchards. 
Pezothrips kellyanus had quickly spread in the whole of the Valencian region. However, important damage was located only in some specific areas. Pezothrips kellyanus populations were associated with citrus tree phenology. Thus, higher population densities occurred during the flowering period. Nevertheless, although in small quantities, we found larvae and adults of P. kellyanus practically during the whole year, developing on mature fruits, extemporal citrus flowers and flowers of other plant species. 
Pezothrips kellyanus showed clumped population distributions on flowers and fruitlets (fruits recently set, of small size),. Immature thrips showed a higher aggregation. Strong correlation between fruit damage by P. kellyanus and the percentage of fruitlets with immature P. kellyanus demonstrated that those life stages were the most harmful. Based on the percentage of fruitlets occupied by larvae, the economic injury levels and environmental economic injury levels were calculated, being 7 and 12%, respectively. A binomial sampling plan is recommended, 310 fruitlets should be monitored weekly from petal fall until the fruits reach 4 cm in diameter. Information for a correct identification of larval stages of P. kellyanus is provided. 
The intensity of the fruit damage caused by P. kellyanus differed among the three years of the study. Those differences were apparently related to the temperature during winter and spring, which in turn affected the onset of the flowering period as well as the survival and development of P. kellyanus populations in citrus and other plant hosts. In spite of the differences in the damaging potential among years, the damage occurred between 300 and 500 degree days for all three years (daily temperature accumulated above 10.2ºC), coinciding with the peak abundance of the second larval stages. The invasive plant white bladderflower (Araujia sericifera Brot.) has been identified as a new host record for P. kellyanus. 
With regard to biological control, 15 soil predatory mite species have been identified. Interestingly, some of them belong to mite families that have been already cited as predatory on thrips. The most abundant predatory mites were: Parasitus americanus, Gaeolaelaps aculeifer, Neomolgus sp. and Pachylaelaps islandicus. Higher populations of G. aculeifer were associated with lower abundance and fruit damage caused by P. kellyanus. We report here data about how distinct factors such as the addition of composting manure or the presence of different plant species affect mite and thrips populations on the soil. Finally, a treatment with chlorpyriphos to the soil had no significant effect on the abundance of soil predatory mites.