No abstract

Studies on the biochemical basis of resistance to Leucinodes orbonalis Guenee and their correlation with shoot and fruit borer damage in five selected brinjal genotypes done at Tamil Nadu Agricultural University, India during June to December 2005 showed that both shoot and fruit of less susceptible genotypes had the higher amount of poly phenol oxidase (PPO), phenylalanine ammonium lyase (PAL) and lignin and lower amount of reducing sugar. Significant negative correlation was found between percent infestation (shoot and fruit) with PPO, PAL and lignin content, whereas it was positively correlated with reducing sugar content. Among the biochemical constituents, PPO, PAL and lignin contents were negatively correlated with reducing sugar but PPO were positively correlated with PAL and lignin content and vice-versa. Keywords: Biochemical basis; resistacace; eggplant; Leucinodes orbonalis. DOI: 10.3329/bjar.v35i1.5876Bangladesh J. Agril. Res. 35(1) : 149-155, March 2010

Rearing methods for Bracon hebetor (Say) (Hym., Braconidae) were investigated in the series of laboratory experiments designed to enhance the yield of the mass rearing of this parasitoid for biological control of lepidopteran field and stored product pests. In these experiments, the effects of parasitoid and host densities on fertility and sex ratio of B. hebetor were assessed. In parasitoid densities, 50 last-instar greater wax moth (GWM) Galleria mellonella (L.) larvae were placed per container and 1, 2, 4, 8 or10 pairs of B. hebetor (one male and one female) were released in each container. In host density study two pairs B. hebetor were introduce in six different densities (10, 20, 30, 40, 50 and 60) of host, GWM per container. A density of ten male-female pairs of B. hebetor produced a higher number of progeny (205 ± 7.07 adults) on 50 last instar larvae of GWM. Similarly, in a host density experiment, a density of 60 last instars GWM larvae produced a significantly higher number of parasitoid progeny (142.0 ± 8.75 adults), followed by 50 last instar larvae (141.0 ± 8.34 adults) among the tested host densities when two pairs of B. hebetor were used. The sex ratio of progenies was male-biased in all studies and there were no significant effects on sex ratio in various parasitoid and host densities. In mass rearing experiment, total number of emerged parasitoids per 200 wax moth larvae was 1091 ± 82.38 adults with mean parasitism rate of 98 ± 0.8%.

The ecto-endo larval parasitoid, Bracon hebetor (Say) is an important biocontrol agent. Effective storage methods for B. hebetor are essential for raising its success as a commercial bio-control agent against lepidopteran pests. The study was undertaken to determine the effect of storage duration on the pupae of Bracon hebetor in terms of pupal survival, adult emergence, percent parasitism, female and male longevity, female fecundity and sex ratio. Three to four days old pupae were stored for 0, 1, 2, 3, 4, 5, 6, 7 and 8 weeks at 4 ± 1 o C. The ranges of time for adult emergence from stored pupae, production of total adult, survivability of pupae, parasitism of host larvae by the parasitoid, longevity of adult female and male and fecundity were 63.0 -7.5 days, 6.8-43.8/50 host larvae, 13.0-99.5%, 0.0 -97.5%, 0.00-20.75 days, 0.00-17.25 days and 0.00-73.00/50 female, respectively. The time of adult emergence and mortality of pupae increased but total number of adult emergence, survivability of pupae, longevity of adult female and male decreased gradually with the progress of storage period of B. hebetor pupae. The prevalence of male was always higher than that of female. Therefore, short-term storage of B. hebetor pupae could be stored for up to 4 weeks without disturbing the functioning of the parasitoid. It is important for sustaining and accumulating large numbers of parasitoids in mass rearing programs and subsequent use of field application.