Life Table Study of a Moth on Different Food Sources and Artificial Diet

Jenn Hoskins
11th September, 2024

Life Table Study of a Moth on Different Food Sources and Artificial Diet

Image Source: Natural Science News, 2024

Key Findings

  • The study from the Federal University of Pelotas, Brazil, found that Rachiplusia nu larvae did not survive on non-Bt corn, wheat, Bt cotton, or Intacta2 Xtend soybean
  • R. nu larvae successfully developed on non-Bt soybean, sunflower, canola, vetch, Persian clover, alfalfa, bean, and forage turnip, similar to those raised on an artificial diet
  • Cry1Ac soybean leaves reduced larval and pupal mass and total fecundity of R. nu, indicating a negative impact on their biological parameters
In the ongoing battle against agricultural pests, understanding the life cycles and vulnerabilities of these pests is crucial. One such pest, Rachiplusia nu Guenée, poses a significant threat to various crops. This polyphagous species can develop on multiple cultivated and non-cultivated host plants, but detailed life history information about this pest on different hosts has been limited. A recent study from the Federal University of Pelotas (UFPel), Brazil, sheds light on this issue by examining the survival and development of R. nu on various host plants, including Bt and non-Bt crops[1]. The study found that R. nu larvae did not survive on leaves of non-Bt corn, wheat, Bt cotton that expresses proteins Cry1Ac and Cry2Ab2, or on Intacta2 Xtend soybean, which expresses Cry1A.105, Cry2Ab2, and Cry1Ac proteins. However, the larvae showed a viable egg-to-adult biological cycle (54%-66.3%) on non-Bt soybean, sunflower, canola, vetch, Persian clover, alfalfa, bean, and forage turnip hosts, similar to larvae raised on an artificial diet. This indicates that while Bt crops are effective in preventing the development of R. nu, non-Bt crops can support their life cycle. Interestingly, the study also found that R. nu was unable to complete larval development on non-Bt cotton, and only 45.2% of larvae reached the pupal stage when fed leaves of Intacta RR2 PRO soybean, which expresses the Cry1Ac protein. The larval and pupal mass of surviving insects on Cry1Ac soybean leaves were significantly lower compared to other food sources, resulting in a reduced total fecundity of approximately 65%. This reduction in reproductive rate indicates that Cry1Ac soybean negatively affects the biological parameters of R. nu. These findings align with previous studies that have examined the impact of Bt crops on various insect pests. For instance, a study on MON 87701 × MON 89788 × MON 87751 × MON 87708 soybean, which expresses Cry1A.105, Cry2Ab2, and Cry1Ac proteins, found high lethality in neonates of Spodoptera cosmioides and Spodoptera albula, and reduced population growth potential in Spodoptera frugiperda genotypes resistant to Cry1 and Cry2 proteins[2]. This suggests that Bt crops can be effective in controlling certain pest species, although the level of effectiveness can vary depending on the pest and its resistance to Bt proteins. Moreover, research has shown that insect pests are increasingly evolving practical resistance to Bt crops, which poses a significant challenge to their continued effectiveness[3]. Fitness costs, which are negative effects of resistance alleles on fitness in the absence of Bt toxins, and incomplete resistance, where resistant individuals have lower fitness on a Bt crop relative to a non-Bt crop, are factors associated with practical resistance. These findings highlight the importance of monitoring and managing resistance to sustain the efficacy of Bt crops. The recent study by UFPel adds to this body of knowledge by providing detailed information on the life history and development of R. nu on various host plants. It underscores the importance of using Bt crops as part of an integrated pest management strategy to control R. nu and other similar pests. However, it also highlights the need for ongoing monitoring and research to address the challenges posed by resistance evolution. In conclusion, the study from UFPel demonstrates that while Bt crops like Cry1Ac soybean can negatively impact the biological parameters of R. nu, non-Bt crops can support their development and reproduction. These findings are crucial for developing effective pest management strategies and ensuring the sustainability of Bt crops in the face of evolving pest resistance.

AgricultureBiochemAnimal Science

References

Main Study

1) Life table study of Rachiplusia nu (Lepidoptera: Noctuidae) on different food sources and artificial diet.

Published 10th September, 2024

https://doi.org/10.1093/jee/toae200

Related Studies

2) Characterizing the lethal and sub-lethal effects of genetically modified soybean expressing Cry1A.105, Cry2Ab2, and Cry1Ac insecticidal proteins against Spodoptera species (Lepidoptera: Noctuidae) in Brazil.

https://doi.org/10.1002/ps.7225

3) Fitness Costs and Incomplete Resistance Associated with Delayed Evolution of Practical Resistance to Bt Crops.

https://doi.org/10.3390/insects14030214


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