Mahbuba Jahan
Professor
Department of Entomology, BAU, Mymensingh-2202
Extensive trials were carried out in the laboratory and field on the use of some indigenous natural enemies, biorational and synthetic pesticides to develop an eco-friendly module for the management of brown planthopper (BPH), Nilaparvata lugens which has emerged as the major pest of rice in Bangladesh. Predation performance and functional response of three predatory spiders namely Lycosa pseudoannulata, Oxypes javanus and Phiddipus sp. Were determined on different instars of BPH. All the three spiders were found to follow the Type-11l Holling model (Sigmoid). Mass-multiplication technique of the spider on different prey species was developed in the laboratory which was tested in the BAU field.
Similarly, the parasitism by Oligosita sp. (Hymenopera: Trichogrammatidae) and Anagrus sp. (Hymenoptera: Mymaridae) were determined which showed a range of egg parasitism from 48 to 56% and 50 to 62% respectively. The life table of the parasitid were assessed where the intrinsic rate of increase, rm and doubling time (DT0) were calculated as a measure for their suitability in using against BPH. Agar media was used as a new technique to maintain the test insects in the laboratory.Both lab bioassays and field tests were carried out to examine the efficacy of four botanicals (Nico-Neem, Nimbicidine, Neemoil, Urmol) and four synthetic insecticides (Baycarb 50 EC, Curatar 5G, Actara 25WG, Decis 2.5 EC) at different concentration in controlling BPH. Data were recorded for killing BPH by knock-down and persistant toxicity at three different times intervals. Bioassays revealed that all the insecticides had knockdown effect and in killing the adult BPH than that of botanicals. The LC50 values for different insecticides and botanicals were calculated and the toxicity order was determined. The foliar insecticide Baycarb and Decis showed higher adult mortality of BPH and natural enemies ultimately resulting in reduction of beneficial in rice eco-system. Their utility and cost-effectiveness have been demonstrated in small scale field experiments at BAU farm. The release of the spider Lycosa in combination with Neem oil (5%) resulted a good control of plant hopper in the field. Application of the combination of Actara 25 WG and Nico neem (5%) was found very effective in eliminating plant-hopper totally is less than half the cost of 3 to 4 sprays of pesticides.
Integrated management, Brown Planthopper, Natural enemies
Experimental field of BAU
Pest Management
1. To integrated management of brown plant hopper;
2. To augmentation and conservation of natural enemies and Nilaparvata lugens with emphasis.
A series of experiments were conducted in the Entomology Laboratory and BAU farm during the period from September 2005 to June 2006 to investigate the abundance of indigenous natural enemies in the rice field and their effects in integrated management of brown plant hopper (BPH), Nilaparvata lugens. The distribution pattern of natural enemies and BPH was studied during the Amon-Boro rice cropping pattern in selected rice fields where no chemical pesticides were applied. Many species of natural enemies were found to exist in the rice field in both the seasons. Study on the seasonal fluctuations of the predatory spiders and carabid beetle in rice fields showed a constant numerical interaction with the prey. In general, a density dependent parasitism was found by the parasitoid. Parasitism by Oligosita sp. (Hymenopera; Trichogrammatidae) ranged from 18 to 51% and 20 to 62% during the boro and Aman seasons respectively. The parasitoid Anagrus sp (Hymenoptera: Mymaridae) showed 17 to 42% parasitism in Boro and 4 to 64% in Aman season.
Bangladesh Agricultural University Research Progress. Volume-19. Proceedings of the Workshop of Bangladesh Agricultural University Research Progress, 08-09 March, 2009.
The performance of the predators and parasitoids as biocontrol agents of BPH studied in the laboratory indicated that the existing natural enemies in the rice ecosystem could be a significant mortality factor through augmentation. For conducting experiments in the laboratory for a considerably longer period of time, Agar media was used as a new technique to maintain the plants, pest and the natural enemies in good condition. Anagrus optabilis (Perkins), an egg parasitoid of Hemipterous hoppers, strongly attacked eggs of brown plant hopper, showing no preference to the Nymph. This parasitoid was found to attack host eggs of any stage of development, even those containing well developed embroys.
Report/Proceedings