| Author | Shrestha, Sunil Man |
| Call Number | AIT Thesis no.AE-92-39 |
| Subject(s) | Pests--Biological control
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | A field trial was undertaken to evaluate the comparative efficacy of different biological
control methods against major cruciferous insect pests on Chinese kale (Brassica alboglabra, Bailey).
The treatments selected for study were the commercial preparation of neem extract (Azadirecta
indica,Juss.) and B t (Bacillus thuringiensis, Berl.) both at two different concentrations i.e 100 cc/20
lit. of water and 50 cc/20 lit of water, three repellent crops viz. citronella grass ( Cymbopogon
wintereanus), sweet basil ( Orimum basilium, L.) and pepper mint (Mentha viridis), a common
chemical insecticide (atabron) and the control.
The major pests monitored in the field were diamondback moth (Plutella xylostella, L.),
cutworm (Spodoptera litura, F.), cabbage webworm (Hellula undalis, F.), ilea beetle (Phylotetra spp.)
and cabbage semilooper ( Trichoplusia ni, Hb.). Among them DBM was found to be most dominant
one.
The yield of Chinese kale obtained from Bt and neem extract (both at higher concentration)
were higher than from atabron. Among the repellent treatments, the highest yield was harvested
from the mint plots, which was also higher than from chemical treatment. Both Bt and neem extract
at the lower concentration gave lower yield than atabron, but statistically not different at 5% level.
Similarly, the biological treatments were found equally or even more (B t at higher
concentration) efficient in killing or driving away the pests in or from the vegetable beds than the
chemical treatment. But unlike the chemical spray, the bio-sprays did not show immidiate effect on
the pests larvae (i.e after 36 hrs of spray), but later (i.e when counted after 5 days of spray), they
have shown a better efficacy than chemical spray causing higher rate of larval mortality. Among the
three repellent treatments, lowest number of DBM larvae were recorded from basil plots, followed
by mint and citronella.
The selected biological methods in the study were found to be more economical to practice
than spraying the chemical insecticide. The dominance analysis has confirmed that B t and neem
spray at higher concentration and mint are the dominant methods which give relatively higher net
revenue at lower variable costs. |
| Year | 1992 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Upasena, Selawa H. |
| Examination Committee(s) | Suthad Setboonsarng ;Verink, Johan
|
| Scholarship Donor(s) | Government of United Kingdom ; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 1992 |