1a. Objectives (from AD-416)
1) Assess seasonal patterns of pathogen incidence in citrus trees and psyllid vector populations in regions of high huanglongbing (HLB) incidence; 2) Evaluate the influence of cultural factors that affect incidence and titer of Liberibacter in citrus trees and psyllid populations including tree age, variety, rootstock, block size, surroundings and HLB management practices such as tree removal and vector control; and 3) refine and update management recommendations based upon seasonal and cultural effects on pathogen incidence and intensity.
1b. Approach (from AD-416)
Objective 1: Seasonal fluctuations in psyllid numbers, in symptom expression in citrus trees and incidence and intensity of Liberibacter infection in both psyllids and plant tissue will be assess over time in insecticide free blocks located at the SWFREC, Immokalee, FL. Nymphs will be collected from flush tissue and adults by sweep net. Trees will be visually evaluated monthly using a disease severity scale for symptoms of HLB. Foliage and psyllids will be assays using real time PCR for presence of HLB. Objective 2: Large field plots will be established within citrus groves of different sizes and management practices in blocks of different varieties of citrus. Psyllids will be monitores and collected as previously described in Obj. 1. Fruit production and quality will be evaluated using grower-supplied yield data supplemented by analysis of fruit quality (size, color, density, and blemish criteria) obtained from the pilot plant, CREC, Lake Alfred where a color vision system is now in operation. Juice quality including acid content and BRIX will be evaluated also. Objective 3: Measures such as vector control and rouging of symptomatic trees are designed to reduce HLB incidence and the spread of greening, to ameliorate the impact of greening on the grove, and ultimately to increase production and maintain a healthy profit margin. Vector management will be most effective when the greatest number of infective psyllids can be suppressed at least cost and collateral damage to beneficial organisms. The information obtained here will provide data on the incidence of infection in vectors related to seasonal and cultural factors to enable growers to optimize their management practices.
3. Progress Report
This research is related to objective 3A of the parent project. The purpose of this research is to assess seasonal patterns of pathogen incidence in citrus and psyllid populations in regions of high HLB incidence, to evaluate the influence of cultural factors that affect incidence and titer of Ca. Liberibacter in citrus and psyllids, and to develop information needed to improve recommendations for management of HLB. Research is being conducted to determine the incidence of HLB in psyllids collected from South Florida, live catches and from suction traps, and shipped to Riverside in ethanol for testing for presence of Candidatus Liberibacter species.