No abstract

Biological control through habitat management leads to sustainable insect pest control. Different types of land composition such as multiple landscapes, patchiness of landscapes enhance the natural enemies which ultimately lead to control of insect pest. Plant characteristics such as flower shape, flower color and blooming period ensures excess food for natural enemies like nectar and pollen. Moreover, some agricultural practices such as tillage, crop rotation, and intercropping influence the natural enemies especially parasitoid and predators. Consequently, they increase longevity and fecundity of parasitoid and predator that help to control insect pest. One of the most important recently used methods is push-pull which consists of semiochemicals called Herbivore-Induced Plant Volatiles (HIPVs). This compound has been used to prevent pest and attract natural enemies.

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Riptortus pedestris (Fab.) (Hemiptera, Alydidae) is one of the most damaging insects of leguminous crops in Eastern Asia but has only recently emerged as a pest in Bangladesh. Eggs, nymphs and adults of R. pedestris are here reported from mung bean (Vigna radiata (L.)) fields in Bangladesh. Two parasitoid species were reared from field-collected eggs of R. pedestris, the solitary Hadronotus pubescens (Motschoulsky) (Hymenoptera, Scelionidae) and a gregarious species of Ooencyrtus Ashmead (Hymenoptera, Encyrtidae). Here we redescribe H. pubescens, treat H. hogenakalensis (Sharma) as a junior synonym, and report aspects of its biology that were investigated under laboratory conditions. The number of eggs parasitized by H. pubescens was constant with eggs up to 48 hours in age, decreasing by 14% for 96 hour-old eggs. As host egg age increased, the parasitoid mean development time increased and the longevity of the parasitoids decreased.

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During the period from December 2016 to May 2017 the study was carried out at the Research Field of Hajee Mohammad Danesh Science and Technology University, Dinajpur in Rabi season to evaluate the efficacy of different organic and inorganic fertilizers on the growth and yield of boro rice (BRRI dhan29). The experiment had eight treatments with three replications and as follows; T 0 : Control, T 1 : 100% N 75 P 12 K 45 S 9 (Recommended dose), T 2 : 50% NPKS + 6 t cowdung ha -1 , T 3 : 75% NPKS + 3 t cowdung ha -1 , T 4 : 50% NPKS + 6 t poultry manure ha -1 , T 5 : 75% NPKS + 3 t poultry manure ha -1 , T 6 : 50% NPKS + 6 t vermicompost ha -1 and T 7 : 75% NPKS + 3 t vermicompost ha -1 . Application of organic and inorganic fertilizers resulted in a considerable influence on the growth and yield contributing characteristics of boro rice (BRRI dhan29). At harvest stage, the tallest plant (94.37 cm) and the greatest number of total tiller per hill (22.10) was recorded from T 4 . The longest panicle (26.48 cm), maximum number of total grain per plant (178.3), the highest weight of 1000 seeds (21.96 g), the maximum grain yield (10.33 t ha -1 ) and straw yield (15.67 t ha -1 ) was also recorded in T 4 treatment. Although the highest biological yield was recorded from T 4 treatment but statistically similar result was found from T 5 treatment. The findings of the study showed that the performance of the treatment T 4 was the best among all treatments in terms of growth and yields. So, the recommendation of this study is amendment of soil with 50% NPKS + 6 t poultry manure ha -1 might be an efficient practice for achieving sustainable higher boro rice (BRRI dhan29) production.

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Population dynamics of spiraling whitefly and its natural enemies on guava orchards are essential for improvement of existing pest control methods. To find out the seasonal abundance of guava whitefly and its natural enemies and levels of infestations were studied on guava orchards severely infested by A. dispersus. Five guava plants were selected randomly. To determine each stage of the insect density, six leaves comprising upper, middle and lower part of each plant were randomly sampled. Sooty mould infested leaves and presence of natural enemies of A. dispersus were also recorded. The highest number of egg mass (5.0) and nymphs (10.0) per leave were found in the month of September. The highest (0.20%) ladybird beetle, Scymnus sp. (Coccinellidae: Coleoptera) and Encarsia sp. (0.15%) were found in the months of October and January, respectively. The number of leaves infested with sooty mould fungus was estimated highest (93%) during October to January. A. dispersus population was peak in the months of August to January and the associated natural enemies may successfully contribute to the existing pest control methods.J. bio-sci. 24: 67-74, 2016