Population growth and within-plant distribution of the striped mealybug Ferrisia virgata (Cockerell) (Hemiptera, Pseudococcidae) on cotton. The striped mealybug, Ferrisia virgata (Cockerell) (Hemiptera, Pseudococcidae), is a widely distributed and polyphagous pest species, which naturally occurs on cotton plants in Brazil. This study evaluated the establishment and population growth as well as the within-plant distribution of F. virgata on four cotton cultivars: CNPA 7H (white fibers), BRS Verde, BRS Safira, and BRS Rubi (colored fibers). The experiment was conducted in a complete randomized design with four treatments (cultivars) and 18 replications of each. Thus, cotton plants of each cultivar were infested with 100 newly hatched nymphs of F. virgata. The number of adult female mealybugs and the total number of mealybugs per plant were quantified, respectively, at 25 and 50 days after infestation. The developmental and pre-reproductive periods were also determined. Furthermore, we verified the distribution of F. virgata on the plant parts at 25 and 50 days after infestation. Ferrisia virgata showed similar growth of 412-fold in the four cotton cultivars studied. Also, the nymphs were spread on infested leaves; the secondgeneration nymphs were spread and established in all plant parts. Our results characterize F. virgata as having much potential as an important cotton pest in Brazil.

We report the occurrence of natural enemies of Plutella xylostela (L.) in organically farmed kale in Pernambuco, Brazil. Seven natural enemies were observed parasitizing or preying on larvae and pupae of P. xylostella - three parasitoids: Cotesia plutellae Kurdjumov (Hym.: Braconidae), Conura pseudofulvovariegata (Becker) (Hym.: Chalcididae) and Tetrastichus howardi (Olliff) (Hym.: Eulophidae), and four predators: Cheiracanthium inclusum (Hentz) (Araneae: Miturgidae), Pheidole sp.Westwood (Hym.: Formicidae), nymphs and adults of Podisus nigrispinus (Dallas) (Hem.: Pentatomidae), and one unidentified species of solitary wasp. Beyond recording these natural enemies, data on predation of P. xylostella larvae in the field and laboratory by C. inclusum are presented.

Plutella xylostella (L.) é uma praga de difícil controle em virtude de seu alto potencial reprodutivo e de causar danos, e ampla distribuição geográfica, além de apresentar resistência a inseticidas. No entanto, as fases de larva e pupa dessa praga são naturalmente parasitadas por Oomyzus sokolowskii (Kurdjumov), favorecendo o incremento do parasitismo natural. Este estudo investigou o efeito da idade do parasitóide, disponibilidade de hospedeiro e fotoperíodo no comportamento reprodutivo de O. sokolowskii. O número de encontros entre parasitóide e hospedeiro e a taxa de parasitismo aumentaram com a idade das fêmeas até 96h. O parasitismo foi maior quando fêmeas do parasitóide receberam diariamente um número constante de hospedeiros comparado à disponibilidade randômica (13,3 versus 8,9 lagartas). A atividade de parasitismo ocorreu até 20 dias de idade e com longevidade semelhante entre os tratamentos (constante = 33,5 d; randômico = 34,7 d). O número de descendentes por fêmea, no entanto, decresceu com a sua idade, sendo o mesmo observado para o número de parasitóides emergidos por lagarta parasitada. A exposição contínua do hospedeiro à luz ou ao escuro por 12h não afetou a taxa de parasitismo; porém, parasitóides apresentaram maior atividade após 3h de exposição à luz. Assim, futuros estudos e possível utilização de O. sokolowskii, em campo, devem considerar a liberações de parasitóides com idade entre 48h e 72h e, preferencialmente, na madrugada para maiores chances de sucesso de parasitismo.

The high reproduction rate, potential to cause damage, wide geographic distribution and resistance to insecticides of Plutella xylostella (L.) makes difficult its efficient control. However, larvae and pupae of this pest are naturally parasitized by Oomyzus sokolowskii (Kurdjumov), providing opportunities to improve the natural parasitism. This study investigated the effects of the age of adult parasitoids, host availability and time of exposure on O. sokolowskii parasitism behavior. The number of larvae encounters by parasitoid females and the parasitism rate increased with parasitoid age up to 96h. The parasitization was higher when wasps received a constant number of hosts daily in comparison with a random number (13.3 versus 8.9 larvae parasitized). Female parasitization activity was maintained up to the age of 20 days in both treatments and exhibited similar longevity (constant host = 33.5 d; and random host = 34.7 d). The progeny produced per female and the number of parasitoids emerged per host significantly decreased as wasps aged. There was no significant effect of the light regime (12h darkness or 12h light exposure) on the parasitization, although parasitoid was more active after 3h of light exposure. Therefore, further studies on field application of O. sokolowskii should consider the release of 48h- to 72h-old parasitoids at dawn as a way to increase the success of host parasitization.