Abstract
A series of experiments were conducted in the field and in the laboratory to study the bioecology of guava whitefly, Aleurodicus dispersus Russell to develop integrated pest management (IPM) package(s) against the pest during November 2001 to October 2004. Field experiments were conducted at two districts Mymensingh and Pabna. Laboratory study was made in the Entomology Laboratory of Bangladesh Agricultural University (BAU), Mymensingh. The guaval whitefly completed its life cycle between 38-49 days. The longevity of adult guava whitefly ranged from 10-15 days during which a female laid 12-24 eggs. Incubation period of the egg ranged from 8-10 days. The time required for 1st, 2nd, 3rd and 4th instar nymphs ranged from 5- 8, 4-5, 8-13 and 9-15 days, respectively. The average lengths of adult, egg, 1st, 2nd, 3rd and 4th instar nymphs were 2.23, 0.30, 0.32, 0.49, 0.78 and 1.10 mm, and the breadths were 0.41, 0.09, 0.16, 0.31, 0.49 and 0.84 mm, respectively. Distribution of guava whitefly in different months of the year revealed that the highest number of adult and nymph, wax and sooty mould covered leaves were found in January. In spatial distribution of the pest it was found to have maximum number of adult and nymph of guava whitefly, wax and sooty mould covered leaves in the middle portion of the twig and in the north canopy of the guava plant. A significant correlation was found between pest population and the weather parameters like temperature, relative humidity, number of rainy days and sunshine hours. Guava whitefly population disappeared totally during May to August. At that time the pest might take shelter in the plants which had broad leaf and bushy in appearance. In screening of guava variety against guava whitefly, the variety "Mukundapuri Misti" was categorized as tolerant and "Kazi Piara" as moderately susceptible variety. The attack of whitefly on guava plant reduced the growth of the plant considerably and the yield loss was accounted as 20.78% to 25.73%. A spider species, Plexippus paykulli was found as the most effective predator of guava whitefly. A parasitoid, Encarsia sp. was also found to parasitize the 3rd and 4th instar nymphs of guava whitefly causing a maximum of 71.66% parasitization in the field population. Cypermethrin was found as the most effective insecticide in reducing the guava whitefly population followed by malathion in both laboratory and field conditions. Karanja oil @ 7.5ml/L, Trix @ 5ml/L and a granular insecticide, carbofuran were also found effective in controlling the guava whitefly. The plant of different ages required different doses of granular insecticide and younger plant showed greater responses to insecticide in reducing the whitefly. Phytotoxicity was noticed when detergents like 'Jet' and 'Wheel powders' were applied as plant protection materials. The highest number of natural enemies was recorded when the plant products were used as control agents. Application of insecticide caused total disappearance of ladybird beetles. The IPM package 4 consisting of mulching, cutting of offshoot, destructing pest stages and applying Cymbush 10 EC or IPM package 1 comprising mulching, cutting of offshoot, destructing pest stages and applying Curaterr 5G could be suggested as the best management practices for guava whitefly. For the immediate control of the pest the IPM package 4 could be preferred while IPM package 1 might be advocated for the safety of natural enemies and ecofriendly environment. The IPM package 2 consisting of mulching, cutting of offshoot, destructing pest stages and applying detergent i.e. 'Trix' could be an alternative in managing the pest and to ensure lower cost and safer environment.