Adding Plant Scents to Traps Doesn't Catch More Citrus Bugs

Jim Crocker
6th April, 2024

Adding Plant Scents to Traps Doesn't Catch More Citrus Bugs

The mean difference in psyllid catch between baited traps relative to their unbaited counterparts after 3 and 7 days in the field cages.

Image adapted from: Pullock et al. / CC BY (Source)

Key Findings

  • In South Africa, researchers tested if adding attractive odors to traps would catch more citrus-damaging psyllids
  • The study found that the added odors did not increase the number of psyllids caught in the traps
  • Higher temperatures sped up the loss of these odors from the traps, potentially reducing their effectiveness over time
Citrus industries worldwide are facing a significant threat from Huanglongbing (HLB), commonly known as citrus greening disease. This disease, caused by bacteria, leads to the decline of citrus trees and has severe economic impacts on fruit production. The bacteria are spread by tiny insects called psyllids. Two types of psyllids are particularly notorious for this: the Asian citrus psyllid, Diaphorina citri, and the African citrus triozid, Trioza erytreae. Researchers from the University of Pretoria[1] have been working on ways to monitor and control the spread of these psyllids. Effective monitoring is key to implementing control methods early and preventing the disease from taking hold. Traditionally, yellow sticky traps have been used to capture these insects for monitoring purposes. The idea is that the bright yellow color attracts the psyllids, they get stuck, and then can be counted to assess the level of infestation. Previous studies have suggested that adding semiochemicals, which are essentially odors that the insects find attractive, could improve the effectiveness of these traps[2]. Semiochemicals mimic the smells of the host plants that psyllids are drawn to, such as citrus trees. In theory, this could make the traps more appealing and increase the number of psyllids captured. In the recent study by the University of Pretoria, the team set out to test this theory. They used field cages to see if a selection of odorants could indeed enhance the trapping of citrus psyllids when added to the yellow sticky traps. They also wanted to understand how environmental factors like temperature and humidity might affect the release of these odorants from their dispensers. Surprisingly, the study found that none of the odorants tested made any significant difference in the number of psyllids caught in the traps, neither under controlled conditions in field cages nor in the open field. This suggests that the psyllids are not as attracted to these odorants as previously thought, or that the conditions in the field affect the odorants' effectiveness. Furthermore, the research showed that temperature did affect how quickly the odorants were lost from their dispensers, with higher temperatures speeding up the process. This loss of odorants over time means that even if they were initially effective, their impact would diminish. These findings have important implications for the monitoring and control of citrus psyllids. Based on this research, the most reliable method for monitoring remains the use of the traditional unbaited yellow sticky traps. This study builds upon earlier research that has sought to understand the spread and behavior of the psyllids responsible for citrus greening disease. For instance, studies on the genetic diversity of Trioza erytreae[3] and the presence of Diaphorina citri in new regions[4] provide crucial background information on the vectors of the disease. Knowing the genetic makeup and distribution of these pests can help in predicting and preventing their spread. Additionally, the discovery of different Liberibacter species in Eastern Africa and their potential distribution[5] underlines the importance of monitoring and controlling the vectors effectively. The bacteria are the root cause of the disease, and understanding where they are most likely to thrive can help target efforts to stop them. In summary, while the idea of enhancing traps with semiochemicals seemed promising, the latest research from the University of Pretoria indicates that, for now, the best approach for monitoring HLB vectors is to stick with the simpler, unbaited yellow sticky traps. This knowledge is invaluable as it helps to direct resources towards the most effective monitoring methods, which is a critical step in managing and ultimately controlling the spread of citrus greening disease.

AgriculturePlant Science

References

Main Study

1) Addition of Selected Plant-Derived Semiochemicals to Yellow Sticky Traps Does Not Improve Citrus Psyllid Captures

Published 3rd April, 2024

https://doi.org/10.1007/s10886-024-01491-0

Related Studies

2) Lemon Terpenes Influence Behavior of the African Citrus Triozid Trioza erytreae (Hemiptera: Triozidae).

https://doi.org/10.1007/s10886-019-01123-y

3) Mitochondrial genetic variation reveals phylogeographic structure and cryptic diversity in Trioza erytreae.

https://doi.org/10.1038/s41598-020-65880-7

4) Detection of Asian Citrus Psyllid (Hemiptera: Psyllidae) in Ethiopia: A New Haplotype and its Implication to the Proliferation of Huanglongbing.

https://doi.org/10.1093/jee/toaa113

5) Distribution of Candidatus Liberibacter species in Eastern Africa, and the First Report of Candidatus Liberibacter asiaticus in Kenya.

https://doi.org/10.1038/s41598-020-60712-0


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