Effect of temperature on the biological parameters of Pink Bollworm

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Context:

• The Pink Bollworm (Pectinophora gossypiella) poses a significant threat to cotton crops globally, including in India, where it has caused substantial yield losses.
• In July 2024, a study titled "Effect of temperature on the biological parameters of Pink Bollworm" was published in the prestigious Nature journal.
• This research delves into how temperature influences the developmental stages and survival rates of gossypiella, offering crucial insights into pest management strategies amidst changing climatic conditions.

Key Findings

The study observed a direct correlation between temperature and various biological parameters of P. gossypiella:

• Developmental Period: The time taken for P. gossypiella to complete a generation decreased significantly with higher temperatures. For instance, the generation completion time was 26.09 ± 3.24 days at 40°C, compared to 42.74 ± 3.12 days at 20°C.
• Survival Rates: Egg hatchability and larval survival rates peaked at 30°C, reaching 81.2% and 86.7% respectively. However, these rates decreased notably at temperatures below or above this range, indicating temperature sensitivity in developmental processes.
• Pupal Weight and Adult Emergence: Pupal weight was found to increase notably at temperatures between 30°C and 35°C, enhancing adult emergence, mating success, and reproductive output.

Temperature Impact on Life Cycle

Temperature variations affected the entire life cycle of P. gossypiella:

• Incubation Period: Decreased significantly across a range of temperatures (20°C to 40°C), influencing the developmental pace from egg to adult.
• Egg, Larval, and Pupal Development: Each stage (egg, larval, and pupal) showed differing durations depending on temperature. Lower temperatures prolonged developmental stages compared to higher temperatures.
• Larval Development: The time taken at each larval instar decreased with increasing temperatures, affecting overall larval duration and impacting population dynamics.

Longevity and Mating Behavior

• Adult Longevity: Decreased with higher temperatures, with females consistently outliving males across all temperature ranges studied.
• Mating Success: Peak observed at temperatures around 30°C to 35°C, with mating success rates reaching 84% to 80%.

Implications for Agriculture and Climate Change

The findings of this study hold significant implications for agricultural practices, especially in the face of climate change:

• Climate Change Impact: With global temperatures projected to rise, understanding how temperature influences pest behavior is crucial for predicting population dynamics and implementing effective management strategies.
• Management Strategies: Insights gained can aid in developing climate-resilient pest management strategies tailored to mitigate the impacts of temperature variations on cotton production.

Regional Impact in India

In India, where cotton cultivation is widespread, P. gossypiella has been responsible for substantial economic losses:

• Damage Assessment: Reports indicate up to 68% yield loss in affected areas, impacting both genetically modified (Bt) and non-Bt cotton cultivars.
• Recent Outbreaks: Central and northern India have experienced recent outbreaks, underscoring the influence of changing climatic factors on pest outbreaks and agricultural sustainability.

Conclusion

• The study not only sheds light on the thermal biology of gossypiella but also highlights the adaptive responses of this pest to varying temperature conditions.
• Moving forward, further research is needed to explore transgenerational effects and the long-term implications of climate change on pest dynamics and agricultural resilience.
• This comprehensive understanding is essential for devising proactive strategies to safeguard cotton crops and ensure food security in a changing climate.

Pink Bollworm Physical Characteristics: Adult: Small, thin, gray moth with fringed wings. Larva: Dull white caterpillar with eight pairs of legs and conspicuous pink banding along its dorsum; reaches half an inch in length. Lifecycle and Damage: Eggs laid by female moth in cotton ball. Larvae emerge, feed by chewing through cotton lint to consume seeds. Damage impacts both fibre and seed oil production. Opens entry for other insects and fungi by disrupting boll's protective tissue. Distribution and Spread: Native to Asia, now invasive in global cotton-growing regions. Reached southern US cotton belt by 1920s; major pest in southern California. Eradicated from continental US by USDA in 2018 using Bt cotton and sterile male release. Resistance and Control in India: Resistant to first-generation Bt cotton (Cry1Ac) in parts of India. Control methods include insecticides, ploughing under harvested fields to halt lifecycle, and destroying unharvested bolls. Additional control through mating disruption, chemicals, and release of sterile males to prevent fertilization of eggs.

PRACTICE QUESTION Q. Which insect, originally native to Asia, has become invasive in global cotton-growing regions, including parts of the United States, and was recently eradicated from the continental United States through a combination of Bt cotton and sterile male releases? A) Cotton boll weevil B) Pink bollworm C) Cotton aphid D) Cotton leafhopper Answer: B) Pink bollworm

SOURCE: DOWN TO EARTH