ABSTRACT
Plutella xylostella (L.) (Lep: Plutellidae), is a destructive pest of brassicaceous crops in the world. Cotesia vestalis (Haliday) is one of most important biological control agents of P. xylostella in the world and Iran. Both of P. xylostella and C. vestalis biology were carried out in laboratory condition. Results showed that development time of immature stages of P. xylostella including egg, Instar I, Instar II, Instar III, Instar IV, prepupa, pupa were 2.39 +/- 0.17, 2.18 +/- 0.17, 2.06 +/- 0.28, 2.14 +/- 0.14, 2.54 +/- 0.12, 0.40 +/- 0.12 and 4.23 +/- 0.23 days, respectively. Longevity of female and male were 28.26 +/- 0.05 and 30.22 +/- 0.05 days. By dissecting the parasitized larvae, the egg incubation period of C. vestalis was recorded 1.73 +/- 0.06 days. In long-term oviposition trials, females laid eggs on P. xylostella larvae for up to 10 days. Larval development of the parasitoid in host only required 6.47 days: the first instar larva required 3.25 +/- 0.047 days; the second instar larva needed 2.78 +/- 0.1 days and the third instar larvae exited the host and pupated in, 0.4 +/- 0.07 days. Prepupal and pupal period of wasp were 1.9 +/- 0.06 and 2.13 +/- 0.09 day, respectively. Unmated female and male longevity of wasp were 16.83 +/- 0.37, 16.25 +/- 0.17 and sex ratio is male-biased. When a mixed group and isolated of instars were presented for parasitoid, the 2nd and 3rd instar larvae were so preferred and the 4th instar was less attractive for selection. In choice experiment, the percentage parasitism of 2nd, 3rd and 4th instars was 78.58, 69.94 and 4.36%, respectively. The rapid oviposition rate, short life duration and high percentage parasitism increases parasitoid potential for suppression of host population. Present results suggest that C. vestalis has considerable potential as a biological control agent for P. xylostella.
Subject(s)
Hymenoptera/pathogenicity , Lepidoptera/parasitology , Animals , Female , Larva/growth & development , Larva/parasitology , Lepidoptera/embryology , Lepidoptera/growth & development , Lepidoptera/pathogenicity , MaleABSTRACT
Sunn pest, Eurygaster integriceps Puton (Heteroptera: Scutelleridae), is one of the major wheat pest in Iran and neighboring countries. In order to control this pest, every year hundred of thousands hectares of wheat crop are sprayed with synthetic pesticides in Iran. Biocontrol, the use of living organisms as pest control agents, became an important alternative to the use of chemical pesticides and, therefore, a potential means of reducing pesticide use and its undesirable effects on human health and the environment. Especially, entomopathogenic fungi offer exciting possibilities as biocontrol agents because of their damaging effects on the target insect host and their ability to cause epizootics. So, in the current study, pathogencity of two isolates (M189, 4556) of Metarhiziurn anisopliae (Metschnikoff) with five concentrations (1x10(4), lx10(5), lx 10(6), 1x 10(7), 1x 10(8)) on adult Sunn pest was evaluated. Each treatment consisted of 30 adults that replicated three times. The adults were dipped in the conidia concentrations for about 10-15 seconds, then were taken and transfered to filter paper to drain off excess liquid. Controls were treated only with distilled water plus Tween 80 (0.02 % ). Treated adults were maintained in growth chamber (25+/-1 degrees C, RH 80+/-5 %) and mortality was recorded daily over two weeks. Probit analysis showed that LCso for M 189 and 4556 were 7.704x10(5) and 3.38x10(5), respectively. The results revealed that isolate 4556 was more effective on Sunn pest than the M189 isolate. Our results showed that different isolates of M. anisopliae have different effects on Sunn pest adult. So, identification, application and screening of different isolates in bioassays will provide a promising potential for finding of efficient isolate to be used in field studies as bio-pesticides.
