Spatiotemporal dynamics of the Southern California Asian citrus psyllid (Diaphorina citri) invasion

Abstract

Biological invasions are governed by spatial processes that tend to be distributed in non-random ways across landscapes. Characterizing the spatial and temporal heterogeneities of the introduction, establishment, and spread of non-native insect species is a key aspect of effectively managing their geographic expansion. The Asian citrus psyllid (Diaphorina citri), a vector of the bacterium associated with huanglongbing (HLB), poses a serious threat to commercial and residential citrus trees. In 2008, D. citri first began expanding northward from Mexico into parts of Southern California. Using georeferenced D. citri occurrence data from 2008–2014, we sought to better understand the extent of the geographic expansion of this invasive vector species. Our objectives were to: 1) describe the spatial and temporal distribution of D. citri in Southern California, 2) identify the locations of statistically significant D. citri hotspots, and 3) quantify the dynamics of anisotropic spread. We found clear evidence that the spatial and temporal distribution of D. citri in Southern California is non-random. Further, we identified the existence of statistically significant hotspots of D. citri occurrence and described the anisotropic dispersion across the Southern California landscape. For example, the dominant hotspot surrounding Los Angeles showed rapid and strongly asymmetric spread to the south and east. Our study demonstrates the feasibility of quantitative invasive insect risk assessment with the application of a spatial epidemiology framework.

Size and shape analysis of Trioza erytreae Del Guercio (Hemiptera: Triozidae), vector of citrus huanglongbing disease

“…The widespread distribution of ACP compared to the more geographically restricted ACT may be indicative of certain morphometric variations that are suitable to dispersal and may prove useful in identifying potential management solutions for the two psyllid species. Using biogeographical data, mayfly, stonefly, and damselfly distribution of the genus Enallagma was correlated with wing size and area . Similarly, future studies should explore possible correlations between the shape of psyllid wings and dispersal capabilities.…”

Effects of Constant and Fluctuating Temperatures on Development Rates and Longevity of Diaphorencyrtus aligarhensis (Hymenoptera: Encyrtidae)

“…Southern California's dense urban environment is largely characterized by unmanaged backyard citrus. These urban trees are reservoirs of D. citri-CLas from which dispersal into neighboring commercial citrus groves may occur (Bayles et al 2017). Because residential zones are rarely under chemical management, biological control is the primary means of suppressing D. citri populations and, consequently, delaying CLas dissemination from these areas into commercial citrus (Hoddle and Pandey 2014).…”

Predicting the fundamental thermal niche of crop pests and diseases in a changing world: a case study on citrus greening

“…However, California has the added disadvantage that its neighboring country and many neighboring states have the disease or have ACP present (Torres-Pacheco et al ., 2013). Indeed, the initial incursion of ACP into California is most likely to have occurred from Mexico (Bayles et al ., 2017). This makes it harder to reduce the likelihood of HLB incursion as it is difficult to control the movement of vectors across borders.…”