The predacious mite Euseius addoensis addoensis (McMurtry) is an important predator of citrus thrips, Scirtothrips aurantii Faure, and Tetranychid mites on citrus in the eastern Cape Province of South Africa. It can also survive and reproduce on certain pollens. In this study, pollen collected from windbreaks commonly used around citrus orchards, was compared with that from Carpobrotus muirii (Mesembryanthemaceae) as a food source for predacious mites. Bioassays were conducted in the laboratory using a leaf-disk technique and both mite mortality and fecundity were recorded through one generation. Casuarina cunninghamiana (Casuarinaceae) was the only windbreak tested that produced pollen capable of sustaining E. a. addoensis for a generation with fecundity similar to that obtained with Carpobrotus muirii. Pollens collected from Pinus radiata (Pinaceae), Cupressus arizonica, C. goveniana and C. torulosa (Cupressaceae) were unsuitable. Casuarina spp. windbreaks may therefore help to maintain predacious mite populations during autumn when natural sources of prey are diminishing.
Citrus (Citrus spp.) production continues to decline in East Africa, particularly in Kenya and Tanzania, the two major producers in the region. This decline is attributed to pests and diseases including infestation by the African citrus triozid, Trioza erytreae (Del Guercio) (Hemiptera: Triozidae). Besides direct feeding damage by adults and immature stages, T. erytreae is the main vector of ‘Candidatus Liberibacter africanus’, the causative agent of Greening disease in Africa, closely related to Huanglongbing. This study aimed to generate a novel barcode reference library for T. erytreae in order to use DNA barcoding as a rapid tool for accurate identification of the pest to aid phytosanitary measures. Triozid samples were collected from citrus orchards in Kenya, Tanzania, and South Africa and from alternative host plants. Sequences generated from populations in the study showed very low variability within acceptable ranges of species. All samples analyzed were linked to T. erytreae of GenBank accession number KU517195. Phylogeny of samples in this study and other Trioza reference species was inferred using the Maximum Likelihood method. The phylogenetic tree was paraphyletic with two distinct branches. The first branch had two clusters: 1) cluster of all populations analyzed with GenBank accession of T. erytreae and 2) cluster of all the other GenBank accession of Trioza species analyzed except T. incrustata Percy, 2016 (KT588307.1), T. eugeniae Froggatt (KY294637.1), and T. grallata Percy, 2016 (KT588308.1) that occupied the second branch as outgroups forming sister clade relationships. These results were further substantiated with genetic distance values and principal component analyses.
24 October 2019 in European Journal of Plant Pathology