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Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) has recently become a pest of citrus whose nymphs feed on the surface of young fruitlets. This feeding habit causes patches or rings of tissue scar around the apex as fruit mature. Currently, little is known about the distribution of P. kellyanus nymphs. Further knowledge would allow the development of an appropriate sampling protocol and targeted pesticide application. In our first experiment, the abundance of first- and second-generation P. kellyanus nymphs was surveyed in a citrus orchard at different times of day to characterize their spatial and temporal distributions. The distribution of damaged fruit was also measured at harvest. Our results showed that P. kellyanus nymphs tended to be present in the upper half of the canopy and mainly damaged the fruit located in this area of the canopy. However, P. kellyanus nymphs were uniformly distributed among the four cardinal directions of the canopy and throughout the day. Consequently, cardinal direction and time of the day seem to be less important when developing a sampling plan or in improving targeting or timing of insecticidal spray applications. In our second experiment, we tracked the presence of P. kellyanus nymphs in labeled fruit daily. These data were used to determine how many days the nymphs occupied a fruit and to relate occupancy and premature fruit abscission. The nymphs of P. kellyanus remained on the same fruit for only 1 d. The rate of fruit abscission in June was significantly higher in fruit occupied by first-generation P. kellyanus nymphs than in nonoccupied fruit.
1 Petroleum-derived spray oils (PDSO) are widely used and recommended in many integrate pest management programmes and in organic agriculture against several pests. However, there are numerous discrepancies in their efficacy against pests and, more interestingly, in their side effects on natural enemies. 2 In the present study, we used the citrus key pest Aonidiella aurantii Maskell (Hemiptera: Diaspididae) and its main parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinedae) as models to evaluate both the lethal and sublethal effects of four commercial PDSO on different instars of the herbivore, as well as on the adult and immature stages of the parasitoid. 3 The four PDSOs displayed similarly high mortalities against young instars of A.aurantii. However, most adult females survived all PDSO applications, and the fecundity of the surviving females was not altered. 4 PDSOs were harmless to the parasitoid A. melinus because the survival (acute toxicity), longevity and fecundity of the surviving adults (sublethal effects) were not affected. Similarly, immature emergence was not affected by any of the four PDSOs after spraying the parasitized hosts. 5 Overall, the results of the present study confirm the environmental-friendly profile of PDSOs against natural enemies and demonstrate a similar performance for PDSOs when they were correctly sprayed under the same conditions.
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