In Brazil, Huanglongbing (HLB) has been managed by removal of symptomatic-trees and Asian citrus psyllid (ACP) control. Although new HLB-affected trees and ACP can be detected all year long, visual detection of HLB-affected trees has been more pronounced from March to August while ACP population densities are higher from September to February. Therefore, the aim of this work was to compare the efficiency of applying the control strategies only during the higher occurrence periods of new HLB affected trees and ACP adults with the control application during all year long. The experiment was carried out in a 4-yr old sweet orange Valencia/Rangpur lime grove and had a 2 by 3factorial design with 3 replications (1.4 ha plots). The factor “HLB-tree elimination” had 2 treatments: monthly elimination all year long; and monthly elimination from March to August, both based on visual inspection. The factor “Vector control” had 3 treatments: monthly ACP control all year long; monthly ACP control from September to February; and ACP control when 10% of 48 yellow sticky traps (YST) placed in the center of plots had at least one adult psyllid. All Treatments of ACP control were done alternating foliar sprays of Provadoâ, Dimetoatoâ, Trebonâ and Marshalâ+Micromiteâ. After 5 years, no significant differences were detected among different treatments for the variables mean cumulative HLB incidence and disease progress rate estimated by linear regression of the last 4 years cumulative disease incidence. The mean cumulative HLB incidence increased from 0.4% to 14.2% (Yr1 4.9%, Yr2 1.9%, Yr3 2.3%, Yr4 1.7%, and Yr5 3.0%). The number of caught ACP per YST per assessment and the area under the curve of percentage of YST with ACP were significantly higher for monthly ACP control from September to February (total of 34 sprays), but did not differed between monthly ACP control all year long (total of 65 sprays) and control based on ACP monitoring with YST (total of 21 sprays). We believe that HLB management wasn’t better because there was a significant amount of new HLB-symptomatic trees (25.2%) found from December to February, and 12.3% of ACP caught in August.  In conclusion, with some adjusts the management of HLB could be optimized according to the favorable periods for HLB-symptomatic trees detection and ACP populations.

Despite the relative effectiveness of recommended measures of inoculum reduction and Asian citrus psyllid (ACP) control to manage HLB, growers still look for nutrient management practices to minimize losses due to expected progress of the Huanglongbing (HLB). However, clear evidence of positive effects of improved mineral nutrition on tree health and productivity is lacking. Therefore, in December 2010 an experiment was set up in a non-irrigated grove of 8-yr-old Valencia sweet orange trees on Rangpur lime to evaluate the effects of nutrients (K, Zn and Mn), phosphate and salicilate applied as a foliar spray to the trees four times in the year during spring and summer. The experiment has 8 treatments in 4 randomized blocks with 1280 trees/plot. ACP has been rigorously controlled in 3 of 4 blocks. At the beginning of experiment the incidence of HLB symptomatic trees was <2%, and 20 HLB-affected trees with mean disease severity <3% were marked. After two years, preliminary results demonstrated that there was no effect among different treatments and that nutritional treatments did not reduce the progress of HLB-symptomatic trees incidence, did not reduce the disease severity progress in marked trees, and did not improve yield of HLB-symptomatic trees. In June 2012, the mean HLB incidence was 8% and 18% for plots with and without ACP control respectively. In September 2012, the mean disease severity on marked trees was 37% independent of ACP control. Compared with ‘healthy’ trees, HLB-symptomatic trees had a mean reduction of 15% and 44% in yield respectively in the first and second years after the beginning of experiment.

The assessment of bacterialiferous Asian citrus psyllid (ACP) frequency is important in epidemiological and management studies because it can be related with the abundance of inoculum sources and with putative new HLB infections. For that, ACP can be collected directly or on yellow sticky traps (YST) commonly used by Brazilian growers to monitor psyllid population. The YST are usually left in the field for 2 weeks after which time YST are visually evaluated for the ACP presence, and if present, the psyllids are removed from the YST and tested by real-time PCR (qPCR) for liberibacter presence. Previous studies in Florida showed that the incidence of Las-positive ACP declined with increasing time on the YST (Irey et al., 2011). Thus, the objective of this work was to determine if time ACP is keep on YST affects qPCR results for Las and if it was related to weather conditions during winter and summer of Araraquara-SP (Brazil). ACP adults from nymphs reared on Las infected trees were placed on YST (BUG-Agentes Biológicos) in the field and 20 samples with 3 individuals were tested after 0, 1, 3, 9, 12 and 15 days. The results were compared with samples directly collected without trap glue. Experiments were done in June, July and August (winter) and in January, February and March (summer). In contrast with previous report in Florida, no difference on the incidence of Las-positive ACP samples was observed up to 15 days on the YST in both seasons.

The assessment of bacterialiferous Asian citrus psyllid (ACP) frequency is important for (i) studies of bacteria acquisition and inoculation by ACP, (ii) disease detection in disease free areas but with ACP presence, (iii) efficiency evaluation of inoculum reduction strategies, (iv) evaluation of frequency of Candidatus Liberibacter asiaticus (Las)-positive ACP and the abundance of inoculum sources or putative new HLB infections relationships. Depending on the conditions and time of storage of collected psyllids, Las DNA in ACP could degrade and Las-false negative results might occur. Thus, this study was conducted to evaluate the detection of Las in ACP adults submitted to different storage methods and time of storage by real-time PCR (qPCR). Two 2x3x7 factorial experiments were conducted. Factors were ‘Ethanol’ (with or without 70% ethanol), ‘Temperature’ (-20°C, 4°C and 26°C) and ‘Time’ (0, 3, 7, 14, 21, 28 and 35 days). For each treatment, 20 samples with 3 ACP adults from nymphs reared on Las infected trees were tested for Las presence by qPCR. No significant differences in percentages of psyllids samples positive for Las were observed among the storage methods up to 35 days, except a slight trend of decline in Las detection in samples storage without ethanol at 26°C after 14 days of storage.