|Publication Type||Journal Article|
|Year of Publication||2005|
|Authors||Esker, PD, Gibb, KS, Dixon, PM, Nutter, Jr, FW|
|Journal||Phytopathology: international journal of the American phytopathological society|
|Pagination||S128 - S128|
The epidemiology of papaya yellow crinkle in Australia was studied by testing hypotheses regarding the influence of tomato big bud (TBB) and sweet potato little leaf V4 (SPLL-V4) phytoplasma strains, papaya plant age, and seasonal (wet/dry) effects on post-incubation time-to-death (TDD) in papaya with survival analysis. Survival analyses were applied to 36-consecutive monthly incidence assessments in a papaya plantation in the Northern Territory, Australia. These methods included Kaplan-Meier estimates of survival functions, accelerated failure time models, and Cox proportional hazards. No differences in TDD between TBB and SPLL-V4 infected papaya were observed. Moreover, neither plant age or seasonal effects influenced TDD. Post-incubation TDD ranged from 4 to 5.5 months. We also used spacetime point pattern analysis to study spatial and temporal dependence for both TBB and SPLL-V4. This approach simultaneously tests the interaction between space and time to quantify space-time windows with increased disease risk. Based on spatial analysis only, SPLL-V4 infected papaya was aggregated upwards of 30 m (10-15 plants along or across rows), whereas TBB-infected papaya was randomly dispersed. However, based on space-time analysis small-scale aggregation of infected plants (< 10 m spatially and < 5 months temporally) for TBB-infected papaya was observed.