Application of 75-150 kg parasi (Cleistanthus collinus) leaves by broadcasting once in the rice field at 3 days after transplanting controls yellow stemborer during kharif. All the rice growers in Aralkocha village of Purulia district in West Bengal follow this practice for the last 50 years.
Results and discussion
Experiments were conducted during rainy season (kharif) of 2002, 2003 and 2004 and during winter season (rabi) 2004. The treatments taken during the experiment of CRRI farm were: (i) use of parasi (75 kg/ha) at 30 days after transplanting (DAT), (ii) use of parasi (75 kg/ha) each at 30, 60 and 90 DAT, (iii) use of parasi (100 kg/ha) at 30 DAT, (iv) use of parasi (100 kg/ ha) each at 30, 60 and 90 DAT, (v) use of parasi (150 kg/ha) at 30 DAT, (vi) use of parasi (150 kg/ ha) each at 30, 60 and 90 DAT, (vii) use of carbofuran (1 kg/ha) at 60 and 90 DAT, and (viii) untreated control and seedlings of Savitri variety at 30 days were transplanted during third week of July. In both the years 2002 and 2003, the insect population were decreased in farmers’ field. Reduction in population was related to the drought and heavy rain situation by the farmers. Yield varied from 5.63 to 6.03 tonnes/ha in comparison to 4.93 tonnes/ha in untreated control. Though the insect did not contribute to significant yield loss due to its less or no infestation, there was an increase in yield with parasi treatment in comparison to that with untreated control.
During rabi season different treatments of parasi leaf application (150 kg/ha) at 10 and 20 DAT and at 10, 20 and 30 DAT were effective in control of insect population than carbofuran. Single application of parasi leaf at 150 kg/ha or 250 kg/ha were next in the order of efficacy, though all the treatments were superior to the untreated control. The same trend of efficacy was also obtained in white ear-head formation and grain yield. In addition to the reduction of YSB infestation, there was an increase in the number of ear-bearing tillers in all the treatments in comparison to the control. But it was more in repeated application of parasi treatments than in single application, which may also increase the grain yield.
Conclusion
Parasi leaf was found effective in controlling yellow stem-borer and thereby increasing the yield of rice when it was applied thrice in rice fields. It has also been found effective in increasing the population of earthworms and soil bacteria.