Comparisons of economic thresholds for Asian citrus psyllid management suggest a revised approach to reduce management costs and improve yield

Authors: CHEN, XUEDONG - University Of Florida; Stockton, Dara; GOSSETT, HUNTER - University Of Florida; QURESHI, JAWWAD - University Of Florida; IBANEZ, FREDDY - Texas A&M Agrilife; PELZ-STELINSKI, KIRSTEN - University Of Florida; STELINSKI, LUKASZ - University Of Florida

Submitted to: Frontiers in Sustainable Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2022
Publication Date: 8/30/2022
Citation: Chen, X., Stockton, D.G., Gossett, H., Qureshi, J.A., Ibanez, F., Pelz-Stelinski, K.S., Stelinski, L.L. 2022. Comparisons of economic thresholds for Asian citrus psyllid management suggest a revised approach to reduce management costs and improve yield. Frontiers in Sustainable Food Systems. 6. Article 948278. https://doi.org/10.3389/fsufs.2022.948278.
DOI: https://doi.org/10.3389/fsufs.2022.948278

Interpretive Summary: First line management of invasive arthropod pests in the U.S. depends on insecticides to knockdown populations. However, even for disease vectors such as the Asian citrus psyllid (ACP), which transmits citrus green disease, high management costs, the development of insecticide resistance, and declines in natural enemies have raised concerns that more conservative management is needed. This study investigated the effect of four different economic thresholds on ACP pest pressure in the field over the course of one year. At the end of the season, yield was assessed and overall losses were estimated using the latest numbers on Florida citrus prices from NASS. The results showed that a reduced spray program based on a relatively high economic threshold of 0.5-1.0 psyllids was sufficient to reduce the number of sprays per year by half, thereby improving profits. Importantly, ACP density in the field remained relatively similar and yield losses did not substantially increase, despite fewer sprays. These data may encourage growers combating HLB in commercial citrus to reevaluate their approach to vector management and use monitoring to dictate when sprays should occur. This has benefits economically and ecologically and improves the mission of sustainable agriculture in the U.S.

Technical Abstract: Huanglongbing (HLB) or citrus greening disease is vectored by the Asian citrus psyllid, Diaphorina citri Kuwayama. Vector control is considered a basic component of HLB management even in high disease incidence scenarios. While control is mostly chemically achieved, overuse of insecticides raises a number of concerns for the development of D. citri insecticide resistance and impacts to environmental sustainability and secondary pest infestation. The present study assessed how the three different economic thresholds (mean of 0.2, 0.5, or 1.0 adult psyllid per stem tap) for D. citri management affected yield and management costs. We also observed the effects on secondary pest and natural enemy populations in the field. The results indicated that an economic threshold of 0.5-1.0 reduced management costs and improved yield, compared to monthly calendar-based sprays. While yield losses were slightly greater compared to the lower threshold of 0.2, management savings of more than 100% made up for this difference. Our data showed that the 0.5 threshold was also associated with lower numbers of citrus root weevils, a secondary pest of citrus. Meanwhile, natural enemy populations were more variable. The 0.5 economic threshold was associated with greater numbers of spiders in the field, but ladybird beetles were greatest in the calendar-based treatment. Together this suggests that implementation of a rotational insecticide spray program based on an economic threshold of 0.5-1.0 adults per stem tap would be beneficial economically and ecologically. We discuss the implications of such an approach in the context of a young tree protection program and the greater goals of sustainable agriculture.