The relationship between the Huanglongbing pathogen and Diaphorina citri with body color polyphenism: field dynamics,...

Phenotypic plasticity is generally regarded as a crucial adaptation that enables organisms to survive in the face of environmental changes. Diaphorina citri, a vector of Candidatus Liberibacter asiaticus (CLas) that causes citrus Huanglongbing, displays three distinct body color morphotypes: blue/green, gray/brown, and orange/yellow morphs. Here, dynamics monitoring of D. citri population in the field was established to identify the occurrence peak. The orange/yellow is a shared phenotype, and hence we focused on the two most prevalent color morphs blue/green and gray/brown. We evaluated the life-history characteristics and susceptibility to insecticides of the two color morphs. For the association between the body color polyphenism and CLas, we compared the CLas acquisition efficiency of field and laboratory populations, and investigated immunological competence of the two color morphs.

Diaphorina citri adults were present in all seasons in year one, with higher incidences recorded in July, August, and September. During these periods, the blue/green morph predominated in the field, while during the overwintering period, the proportion of gray/brown morph increased. Population parameters showed no significant differences between the two color morphs. Additionally, gray/brown morphs were more susceptible to insecticides and CLas acquisition. Furthermore, the two color morphs displayed different immune responses to pathogen infection.

The CLas infection rate was closely associated with color morphology in D. citri. Different field distribution and trait combinations of the two color morphs represent their responses to variable environments. This study not only broadens the understanding of color polyphenism, but it may also provide potential implication for controlling strategies in D. citri. © 2025 Society of Chemical Industry.