Abstract
The research work on bioecology and management of stemfly, Ophiomyia phaseoli (Tryon)
(Diptera: Agromyzidae) on blackgram was carried out at the Breeder Seed Production Centre,
Bangladesh Agricultural Research Institute, Debiganj, Panchagarh, Bangladesh. Adults
started mating soon after emergence and a single female laid on an average of 17.7 eggs
during 13.7 days of oviposition period. The mean duration of egg stage was 2.4 days and the
larva passed through three instars. A period of 8-11, 9-11 and 18-23 days were required to
complete larval, pupal and total life cycle of O. phaseoli, respectively. Significant variation
among the planting times initiating from Aug 07 to Sept 11, 2003 at an interval of seven days
became well pronounced to minimize O. phaseoli infestation. The Aug 21 showed the best
planting time to reduce stemfly infestation and to obtain maximum seed yield followed by
Aug 07 and Aug 14 plantings. In general, third-fourth week of crop age was the most
vulnerable for stem tunneling by O. phaseoli. The maximum avoidable loss of blackgram due
to stemfly infestation was estimated to be 35.08%. Altogether 20 lines/varieties were
screened under natural field condition against O. phaseoli but none of them found totally free
from its infestation. Among them, only two lines BМАР-9139 and 86186 were found
promising against stemfly. The mulching with rice straw, water hyacinth and weed stubble
appeared totally ineffective to combat stemfly infestation. The influence of intercropping
with blackgram + maize, blackgram + brinjal, blackgram + groundnut against stemfly
infestation indicated that blackgram with maize proved the most effective intercropping
combination, reduced 51.38% and 57.31% plant infestation and stem tunneling, respectively
over sole blackgram crop, gave the highest blackgram equivalent yield, highest net return and
incurred the highest BCR value of 2.12. While insecticidal properties of some indigenous
plant extracts and synthetic chemical insecticides were evaluated it was found that synthetic
insecticides in general, showed significantly better performance compared to botanical
pesticides against O. phaseoli. Application of Carbofuran as seed treatment was found as
most economic and effective treatment followed by combination of Carbofuran as seed
treatment and Dimethoate spray at 30 days after sowing (DAS). To develop an integrated
management approach against stemfly of blackgram seven treatments viz. T₁= Line BMAP9139 sown on Aug 21, T2 = T₁ + Intercropping with maize, T3= T₁+ Seed treatment with
Carbofuran, T4= T₁+ Seed treatment with Carbofuran + Intercropping with maize, T5= T₁+
Seed treatment with Carbofuran + Spray of Dimethoate @ 2 ml/l at 30 DAS, T6= T1 + Seed
treatment with Carbofuran + Spray of Dimethoate @ 2 ml/l at 30 DAS+ Intercropping with
maize and T7 = T₁ with farmers practice were tested. Among those, the treatment To gave
lowest number of larvae and pupae per plant, percent infested plant and stem tunneling and
highest yield followed by Ts and T4. Considering BCR, the treatment Ts appeared the best one
as it gave the highest BCR (2.81). Therefore it is concluded that early planting with
promising varieties along with seed treatment with Carbofuran and one additional spray with
Dimethoate might be suggested for blackgram growers of Bangladesh to minimize stemfly
infestation and to obtain maximum economic return.