Model Answer
0 min readIntroduction
Rice, a staple food for over half the world’s population, is vulnerable to numerous pests and diseases. Among these, the Brown Planthopper (BPH), *Nilaparvata lugens*, stands out as a significant threat, causing substantial yield losses across Asia. Its ability to rapidly develop resistance to insecticides and its transmission of rice tungro virus make it a particularly challenging pest to manage. Understanding its biology, damage potential, and effective control strategies is crucial for ensuring food security. This answer will detail the systemic position of BPH, its life cycle, the damage it inflicts, and measures for its prevention and control.
Systemic Position of Brown Planthopper (*Nilaparvata lugens*)
The Brown Planthopper belongs to the insect order Hemiptera, commonly known as true bugs. Its taxonomic classification is as follows:
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
- Order: Hemiptera
- Suborder: Auchenorrhyncha
- Family: Deltocephalidae
- Genus: *Nilaparvata*
- Species: *lugens*
It is a member of the planthopper family, characterized by their wedge-shaped head and hind legs adapted for jumping. The BPH is a phloem-feeding insect, meaning it extracts sap from the rice plant’s vascular tissues.
Life Cycle of Brown Planthopper
The BPH exhibits incomplete metamorphosis, progressing through nymphal stages without a pupal stage. The life cycle consists of the following stages:
- Egg: Females insert eggs into the rice leaf sheath in clusters of 10-20. Eggs hatch in 3-7 days depending on temperature.
- Nymph: There are five nymphal instars. Nymphs are initially pale green and become brownish as they mature. They feed on the plant sap and undergo molting between each instar. The entire nymphal period lasts 7-10 days.
- Adult: Adults are small (approximately 6-8 mm long), brownish, and have transparent wings. Females can lay up to 300 eggs during their lifespan of 20-30 days.
The entire life cycle, from egg to adult, can be completed in approximately 21-30 days under favorable conditions (28-32°C and high humidity). Multiple generations can occur within a single rice-growing season, leading to rapid population build-up.
Damage Caused by Brown Planthopper
The BPH causes damage through direct feeding and indirect effects:
- Direct Feeding Damage: Nymphs and adults suck sap from the rice plant, leading to weakening of the plant, stunted growth, and reduced tillering. Heavy infestations can cause “hopper burn,” characterized by drying and yellowing of the leaves.
- Virus Transmission: BPH is a vector for several rice viruses, most notably the Rice Tungro Virus (RTV). RTV infection causes severe stunting, yellowing, and reduced grain filling, leading to significant yield losses.
- Honeydew Secretion & Sooty Mold: BPH excretes honeydew, a sugary substance, which promotes the growth of sooty mold fungi on the leaves. Sooty mold reduces photosynthetic efficiency.
Damage is most severe during the tillering and panicle initiation stages of rice development. Yield losses can range from 10% to 100% depending on the severity of the infestation and the presence of RTV.
Prevention and Control Measures
Effective BPH management requires an integrated pest management (IPM) approach:
- Resistant Varieties: Planting rice varieties with resistance to BPH and RTV is the most sustainable control measure.
- Agronomic Practices:
- Synchronized Planting: Planting rice crops over a large area simultaneously disrupts the pest’s life cycle.
- Optimum Plant Density: Avoiding excessive plant density reduces microclimate favouring BPH.
- Proper Fertilization: Balanced nutrient application enhances plant vigor and resilience.
- Water Management: Intermittent flooding can reduce nymph populations.
- Biological Control: Utilizing natural enemies of BPH, such as parasitic wasps (*Anagrus* spp.) and fungal pathogens (*Beauveria bassiana*), can help regulate populations.
- Chemical Control: Insecticides should be used judiciously and only when economic threshold levels are reached. Rotation of insecticide groups is crucial to prevent resistance development. Neonicotinoids and organophosphates are commonly used, but resistance is widespread.
- Monitoring and Forecasting: Regular field monitoring using pheromone traps and visual inspections helps detect early infestations. Weather-based forecasting models can predict BPH outbreaks.
Conclusion
The Brown Planthopper remains a formidable threat to rice production. A holistic IPM strategy, prioritizing resistant varieties, sound agronomic practices, and biological control, is essential for sustainable management. Judicious use of insecticides, coupled with continuous monitoring and forecasting, can minimize yield losses and ensure food security. Further research into novel control methods and the development of BPH-resistant rice varieties are crucial for long-term success.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.