Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Trichogramma Zahiri Polaszek Sp.n. (hymenoptera:ttrichogrammatidae): It`s Development Period, Sex Ratio and Parasitism Pattern on Rice Hispa Eggs

Md. Nazmul Bari
Senior Scientific Officer
Entomology Division, BRRI, Gazipur-1701

Md. Fazle Rabbi
PSO
Entomology Division, BRRI, Gazipur-1701

Abstract/ Executive Summary:

Development period, sex ratio and pattern of parasitism of Trichogramma zahiri Polaszek sp.n., an egg parasitoid of rice hispa Dicladispa armigera (Olivier), was studied at the Bangladesh Rice Research institute, Gazipur during 2002-2004. The development period of the parasitoid from egg to adult varied in different months irrespective of sex. The development period averaged 8.54 days (range 7.14-9.64) for the male and 8.58 days ( range 7.17-9.53) for the female and the difference between the sexes was insignificant. The development period was longest in April and shortest in May for both the sexes. The sex ratio was always female biased. Hispa eggs suffered 11 to 68% parasitism from T. zahiri, peaking in August. Multiple parasitisms were found to be common and always dominated over solitary parasitism. The low temperature and relative humidity during December to February had a negative effect on survival of the immature stages of T. zahiri, resulting in very low parasitism rates of hispa eggs.

Keywords: Rice hispa, Dicladispa armigera, Trichogramma zahiri, Egg parasitism

Location: BRRI, Gazipur

Start Date: 01-07-2002

End Date: 30-06-2004

Program Area: Pest Management

Commodity: Rice

Objectives:

To estimate the rate and pattern of field parasitism during different time of the year and development duration and sex ratio of the parasitoid, T. zahiri.

Methodology:

The rice plants with hispa eggs were placed dispersedly in a rice field and retrieved after 24h. Parasitization of the eggs by T. zahiri could not be detectable visually until adult emergence. Therefore, one hundred hispa eggs were sampled randomly from the plants. The leaves were cut in to small pieces with individual hispa egg inside the leaves and placed individually inside small vials with few drops of water to keep inside moist. The eggs were observed everyday for the emergence of adult parasitoids and the number of parasitoids emerging from a single parasitized egg was recorded. Daily temperature and relative humidity was recorded from both field and laboratory to determine correlation, if any existing between climatic factors and parasitism rate. Development period of the parasitoid from egg to adult was calculated from the day of placement of hispa eggs in the field to adult emergence. The sex of the parasitoid was determined based on the difference of the shape of the antennae studied under a binocular microscope. The secondary sex ratio was calculated form the sampled population and expressed as female proportion. Total parasitism rate at different times of the year was calculated as number of parasitized eggs divided by the number of total eggs observed and represented as percentage.

Source of Information: Bangladesh Journal of Entomology. Vol.15, No. 1 Page 45-55.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The one-way analysis of variance showed a significant variation in development (egg to adult) duration of T. zahiri in different months irrespective of sex. The mean development duration of the parasitoid ranged from 7.16 to 9.55 days, irrespective of sex. The year round mean development duration for male and female ranged from 7.14 to 9.64 days and 7.17 to 9.53 days, respectively. The development period for both male and female also varied significantly in different months. Development period for both male and female was the longest in the month of April and shortest in May. Unlike other Trichogrammatid egg parasitoids, female T. zahiri did not take significantly longer time to reach adulthood. The two-sample (paired) t-test did not show significant variation in the development period of male and females in different months (P>0.05). The sex ratio of the emerged T. zahiri was always female biased (60-76%), peaking in July-August. The female biased sex ratio was previously reported in many parasitoid species. Rice hispa eggs suffered zero to 68 percent parasitism during different months of the year from July 2002 to June 2003. The Maximum parasitism rate was observed in August after which a decreasing trend was observed. No parasitism was observed during December to February. Egg parasitism was again observed in March and continued until November. Similar pattern was observed during 2003-2004 with an exception in the month of April and May. Parasitism was comparatively lower during 2003-2004 than that in 2002-2003. The absence of egg parasitism in December to February might be due to very low relative humidity and temperature. During December to February, there was a sharp decline in temperature and relative humidity, which might have caused desiccation of the eggs and hence the parasitoids failed to emerge. On the other hand, parasitoid eggs might not have developed at all due to very low temperature.

Knowledge Management: Journal