Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2018
Publication Date: 10/16/2018
Citation: Owusu, F.A., Tanga, C.M., Paris, T.M., Allan, S.A., Mohamed, S.A., Khamis, F.M., Setamou, M., Borgemeister, C., Ekesi, S. 2018. Size and shape analysis of Trioza erytreae Del Guercio (Hemiptera: Triozidae), vector of citrus huanglongbing disease. Pest Management Science. 75(3):760-771. https://doi.org/10.1002/ps.5176.
DOI: https://doi.org/10.1002/ps.5176

Interpretive Summary: Several species of psyllids serve as vectors of huanglongbing, one of the most devastating diseases of citrus worldwide. Psyllids can feed on a range of citrus host plant species, some of which are better hosts than others. Previously, quantitative studies of size and shape, i.e., morphometrics, revealed that rearing a psyllid on host plants can affect the biology and morphometrics of Asian citrus psyllids. In this study, conducted by scientists at International Centre of Insect Physiology and Ecology, Nairobi, Kenya, in collaboration with scientists from USDA-ARS Center for Medical, Agricultural and Veterinary Entomology, Gainesville, FL, the effects of different host plant species were evaluated on the African citrus psyllid, also a vector of huanglongbing. The study showed that feeding on some host plants resulted in larger African citrus psyllids while other plants resulted in smaller psyllids. The differences in size and/or shape of the African citrus psyllids can greatly affect biological fitness parameters and potential for dispersal to other host plants. These data establish a foundation for the impact of plant feeding that can contribute to the spread of the invasive African citrus psyllid infestations and its related disease risk thus guiding psyllid management strategies.

Technical Abstract: BACKGROUND: The African citrus triozid (ACT) Trioza erytreae Del Guercio (Hemiptera: Triozidae), is one of the most devastating pest of citrus with a well-known role as a vector of the phloem-limited bacteria [Candidatus Liberibacter africanus] associated with huanglongbing (HLB; citrus greening disease), currently considered the world’s most serious disease of citrus. HLB causes colossal losses as it continues to spread rapidly with expanding geographic range of the disease, threatening citrus industries in new areas. Although, the pest can successfully develop and reproduce on several other host plants beside citrus, there is no documented information on the influence of plant species on ACT size and shape. This study seeks to determine the effect of six optimal plant species on ACT size and wing shape when reared under controlled laboratory conditions. METHOD: ACT was reared on six different optimal host plant species for five successive generations; Citrus limon, Citrus sinensis “Valencia”, Bergera koenigii, Citroncirus spp., Clausena anaisata and Citrus tangelo. Adults were examined for morphometric variation using traditional and geometric analysis based on 19 traits or 17 landmarks. RESULTS: The different host plant species were found to have differential morphometric effects on ACT body and wing size as well as wing shape. Based on the wing aspect ratio, females had significantly higher values than males on all the plant species tested. ACT reared on C. limon and Citroncirus spp. were significantly larger than those reared on the other host plant species. ACT reared on C. anisata and C. tangelo were consistently smaller than those from B. koenigii and C. sinensis. Based on wire-frame network visualization, ACT reared on Citroncirus spp. and B. Koenigii had narrower wings than those reared on C. anisata, C. limon and C. sinensis with slightly broader wing patterns. CONCLUSION: This study demonstrates for the first time the impact of host plant species on morphometric variation of ACT, which might have direct impact on the biological fitness parameters of the pest as well as its potential for dispersion. However, additional studies to understand the behavioral and physiological differences associated with the observed phenotypic differences is urgently needed.