Recently, planthoppers outbreaks have intensified across Asia resulting in heavy rice yield losses. The problem has been widely reported as being induced by insecticides while other factors such as global warming that could be potential drivers have been neglected. Here, we speculate that global warming may increase outbreak risk of brown planthopper (Nilaparvata lugens Stål.). We present data that demonstrate the relationship between climate variables (air temperature and precipitation) and the abundance of brown planthopper (BPH) during 1998–2007. Data show that BPH has become significantly more abundant in April over the 10-year period, but our data do not indicate that this is due to a change in climate, as no significant time trends in temperature and precipitation could be demonstrated. The abundance of BPH varied considerably between months within a year which is attributed to seasonal factors, including the availability of suitable host plants. On the other hand, the variation within months is attributed to fluctuations in monthly temperature and precipitation among years. The effects of these weather variables on BPH abundance were analyzed statistically by a general linear model. The statistical model shows that the expected effect of increasing temperatures is ambiguous and interacts with the amount of rainfall. According to the model, months or areas characterized by a climate that is either cold and dry or hot and wet are likely to experience higher levels of BPH due to climate change, whereas other combinations of temperature and rainfall may reduce the abundance of BPH. The analysis indicates that global warming may have contributed to the recent outbreaks of BPH in some rice growing areas of Asia, and that the severity of such outbreaks is likely to increase if climate change exaggerates. Our study highlights the need to consider climate change when designing strategies to manage planthoppers outbreaks.

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Integrated Pest Management (IPM), developed by the Bangladesh Rice Research Institute (BRRI) for management of rice insect pests, was demonstrated and validated through intensive investigation in farmer's fields of Pirganj and Taraganj in Rangpur district during 2012-2014 in two T. Aman and Boro seasons. A portion of each farmer's field kept under the respective farmers' supervision without any intervention, which was treated as control treatment (T4). The other portion was managed with three treatment combinations ie, T1=Prophylactic use of insecticide, T2=Perching + sweeping + need based insecticide application and T3=Perching only. BRRI dhan52 and BRRI dhan58 were used in Aman and Boro seasons respectively. RCB design was followed with eight replications for data analysis. The insect infestation was monitored fortnightly by visual counting from 20 hills and also 20 complete sweeps. The insect infestation, yield and yield contributing characteristics were analysed by one way analysis of variance by Tukeys' post hoc test. The objective of this studies were to validate and demonstrate the IPM techniques in farmers' field. Yellow stem borer, rice leaf roller, long horned cricket, grasshopper, green leafhopper, brown planthopper, white-backed planthopper and gall midge were found as pests in both the locations. However, insect infestation was below the economic threshold level (ETL). No significant differences were observed for insect infestation among the treatments. Natural enemies eg, spider, ladybird beetle, dragon fly, damsel fly, carabid beetle and staphylinid beetle were noticed in both the locations. In some seasons and also locations some natural enemies were not found particularly where indiscriminate/continuous insecticide was used. Thus, it was indicated that indiscriminate/continuous use of insecticide has the detrimental effect on the population of natural enemies. Also, refrained from insecticide application at early crop stages (30-40-day after transplanting) natural enemy populations increased, which might reduce insect population below the ETL. Significantly lower yield was observed at farmers managed fields in both the locations. Therefore, it was found that indiscriminate/continuous use of insecticide had no effect on yield and yield contributing characters of rice, when insect infestation below the ETL. So, farmers could avoid continuous/indiscriminate use of insecticide, which might ultimately save production cost and the environment from insecticidal pollution as well.

Trichogramma zahiri Polaszek sp. n. is described from Bangladesh. It has been collected at several localities from the major pest of rice Dicladispa armigera (Olivier) on which it has an important controlling impact. Trichogramma zahiri is compared with known Trichogramma species from the region, and diagnostic differences are presented. Data on developmental period, adult longevity, egg-laying frequency, host egg age preference and seasonal parasitism rate are presented and discussed. Other records of parasitoids of D. armigera are briefly reviewed and discussed.

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