Rice brown planthopper (BPH) also known as Nilaparvata lugens is a very serious pest that attacks rice plants. It attacks the crop from late vegetative stage to grain hardening stage. Both the nymphs and adults suck the plant sap resulting in chloroting, wilting and drying up of the rice plant. This feeding damage can be seen in the rice field as brown patches which is known as ‘hopper burn’, resulting in serious rice yield loss (>90%) if appropriate control measure is not taken immediately. Beside the damages done by the BPH, it also serves as the vector of Grassy Stunt and Ragged Stunt Virus.
Hence, in order to control this menacing pest, farmers rely heavily on chemical insecticide and somehow the chemical insecticides are often misused leading to negative effects on the ecosystems and human health. Besides, continuous application of synthetic insecticides can trigger resistance evolution in this pest and to make it worse, also destroying the natural enemies of this pest.
Over generations, the utilization of plant materials to protect field crops and stored commodities against pests has been practiced traditionally throughout the world. Many of the plant species concerned also have been used in traditional medicine by local communities and have been collected from the field or specifically cultivated for these purposes. There are approximately 2,500 plants in 247 families that have shown toxic effects against insects. Now, with a trend towards more sustainable pest management, which includes application of bioproducts, is on the rise, thus I’m taking part in this research too.
Botanical approach:In my study, we (my supervisor and I) have selected several allelopathic weed species where the extracts of the plants were tested against the BPH. The idea of choosing those weed species was based on literature search about previous studies where they serve as insecticidal, larvicidal, antifungal, antibacterial, anticancer and etc. Moreover, these species can be found abundant in nature. Due to their adamant eradication, it is possible to explore their beneficial potential or purposes against insect pest. It is very important to recognize the benefits of all species within the crop field including the crops and the weeds. We know that weeds are considered as unwanted plants that often cause interruption in our daily activities, nevertheless weeds can also offer ecosystem services, such as soil erosion protection (cover crops) and pollination services for the benefit of insects. Therefore, we need to explore more about the potential of weeds as source of benefical bioproducts.
Chromolaena odorata (Siam weed or devil weed) and Mallotus paniculatus (Turn-in-the-wind) are common weeds in Malaysia. C. odorata comes from Asteraceae family while M. paniculatus is from Euphorbiaceae. These families are very notable to have insecticidal properties that can deter insects. These two weeds can be easily found along roadsides, in open/abandoned land, cultivated land and plantation areas. They are considered as noxious weeds because they disturb agricultural land very seriously in Malaysia. Rather than eradicate these weeds, we can utilize them to control insect pest particularly brown planthopper in my case.
In my study, several processes included are plant extraction, chemical profiling, mortality screening of plant extract against BPH at different rates, and to make our research deliver continuous impact and benefits to the community, we are also exploring on formulations quantification for these extract so they can become an alternative bioinsecticides for farmers to use.
Future innovation Exploration on the chemical compounds from chemical profiling will be able to design a new formulation of bioinsecticide for crop protection purposes. This innovation will be able to increase the efficacy of the plant extract, yet providing an environmentally friendly pesticide in achieving sustainable agriculture. From this approach, we can reduce the usage of chemical insecticide and provide a better environment for our next generations.
Nor Ilya Binti Mohd Zaki, Malaysia