540 The informational needs of the multidisciplinary audience attending monthly irradiation oncology palliative care rounds at the Toronto Sunnybrook Regional Cancer Centre — needs assessment

Abstract

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae) vectors a bacterium, ‘Candidatus Liberibacter asiaticus’ (CLas), associated with one of the world's most serious diseases of citrus, huanglongbing (HLB) (also known as citrus greening disease). There is no known cure for this disease, which severely reduces tree productivity and fruit quality and promotes tree decline and death. Most growers apply insecticides to control ACP as a tactic to prevent or reduce the incidence of HLB. Plant resistance to ACP may be a viable tactic for managing ACP and CLas. Resistance to colonization by ACP populations has been reported in the genotype Poncirus trifoliata L., which is cross compatible with citrus. The Citrus Research Center (CRC) in Riverside, California, maintains a large number of accessions of P. trifoliata. We conducted four free-choice experiments with 29 CRC accessions of P. trifoliata and found that ACP deposited fewer eggs on 19 of those accessions compared with susceptible sweet orange, Citrus sinensis (L.) Osbeck. Subsequent infestation densities of nymphs generally reflected reductions in oviposition but there were notable exceptions. Some accessions may be susceptible to oviposition but contain traits that confer antibiosis to nymphs. In no-choice experiments with seedling plants representing eight P. trifoliata accessions, oviposition rates were reduced compared with sweet orange and it appeared that factors associated with mature leaves were involved. In no-choice experiments with adult ACP confined to flush cuttings, large reductions were observed in the number of eggs and nymphs on each of five P. trifoliata accessions compared with sweet orange. Based on these results in conjunction with published reports, accessions were identified that consistently showed resistance to oviposition. However, the level of resistance in these accessions has been variable possibly due to environmental conditions, plant age, proximity of plants to susceptible germplasm, and other factors.