A new study has found that the total developmental period of Pink Bollworm shortens with an increase in temperature and survival rate of the larvae also increases.
Pink Bollworm or Pectinophora gossypiella is a pest that has impacted cotton worldwide, including in India.
The research titled Effect of temperature on the biological parameters of pink bollworm, Pectinophora gossypiella Saunders (Lepidoptera: Gelechiidae) was published in the Nature journal on July 1.
The researchers studied the effect of temperature on life parameters of the insect to assess its thermal fitness.
The analysis noted that P. gossypiella took less time to complete a generation from egg to adult at 40°C in a time frame of 26.09 ± 3.24 days against 42.74 ± 3.12 days recorded at 20°C, respectively.
“Hence, P. gossypiella can complete more generations in a season/year under high thermal regimes. Furthermore, the percent egg hatchability and larval survival reached up to 81.2 and 86.7% at 30°C; whereas, it was comparatively lower at 20 and 40°C, indicating that any variation (low or high) from the normal range affects the developmental process,” it added.
Pupal weight was found to be higher at 30 and 35°C, resulting in increase in adult emergence, mating success and higher ability to produce offspring.
Further,the incubation period decreased substantially when exposed to a temperature of 20 to 40°C.
The findings showed that mean duration of egg, larval and pupal development was significantly longer at 20 degrees Celsius compared to 40 degrees Celsius.
Similarly, the larval developmental time decreased as temperature increases at each instar (developmental stage) and the total duration of larvae also differed significantly at respective temperatures.
The study found that adult longevity decreased with increasing temperatures while females outlived males across all defined temperature ranges.
The researchers said their findings are consistent with other studies that found larval mortality of Spodoptera frugiperda and P. gossypiella to be higher at 18 and 37°C.
The mating success was also observed to be higher at 84 and 80 per cent at 30 and 35°C. Furthermore, the study found that insects can alleviate the thermal stress and steadily recover over generations by compromising some developmental traits, enabling it to establish itself in diverse environments.
The research was conducted considering the impacts of climate change on agriculture, which has become a major concern in recent years with global temperatures expected to rise between 1.5 and 4.5°C by 2100.
Such change in temperatures influence physiological responses among species specific to abiotic factors such as temperature, humidity, rainfall and photo-period.
The findings thus offer crucial insights for estimating population dynamics of the pest at field level and developing climate resilient management strategies in cotton, the authors noted.
In India, P. gossypiella has reportedly caused damage to cotton fields, resulting in up to 68 per cent yield loss and 37.5 per cent locale damage equally among Bt-cotton and non-Bt cultivars.
In October 2023, when DTE visited farmers in Rajasthan, Punjab and Haryana, many of the reported damages were up to 90 per cent.
The research noted, “In recent years, the infesttion of P. Gossypiella was observed in central and northern parts of India; the outbreak of this pest was affected by changes in climatic factors. However, the information regarding thermal effects on the life history traits of P. gossypiella and its transgenerational effect is minimal.”