Novel multi-metal systemic bactericide for HLB control

Novel multi-metal systemic bactericide for HLB control

Report Date: 10/11/2019
Project: 18-020   Year: 2020
Category: CLas Bacteria
Author: Swadeshmukul Santra
Sponsor: Citrus Research and Development Foundation

Field trials for efficacy against HLB and canker were continued with sprays every 21 days through October. Harvest for the second year of the grapefruit field trial was completed in the 2nd week of November, yield was weighed and canker rated, fruit size and juice quality are underway after a delay due to equipment failure. Data analysis of this years results and planning for the final year of field trials are ongoing.

Material characterization under various conditions were continued. Studies with citrus seedling were initiated to determine the rate of vascular movement of the metalic content in the stem leaves. Spectroscopy studies were also carried out to study potential biochemical changes of the plants as a result of the treatment. Optimization of the treatment conditions will continue in the next reporting period. Data analysis of the different results is underway with implementation of multivariate analysis.

We determined aquatic toxicity as an endpoint study of where these metal based bactericides would end up within the environment and affect the organisms there. We designed this experiment in accordance with the approved IACUC on fathead minnows with time point readings every 12h run for 48 hours. We tested various concentration ranges of the treatments to determine at what point within a 48h span the population of the fish would be reduced by half. Each concentration was done in triplicates and the data shown is a result of those averages. The LC50 was recorded for each treatment which includes (concentrations in ppm for the respective metal compounds): NAC-ZnO (0.6, 0.4, 0.2), NAC-ZnO+Cu (0.2/0.05), NAC-ZnS (0.6, 0.4, 0.2), NAC-ZnS+Cu (0.2/0.04), ZnO CR-41 (0.6, 0.4, 0.2), Zinc Nitrate (0.6, 0.4, 0.2), NAC (0.5, 1), Copper Sulfate (0.05), Kocide 3000 (0.4), Mg-Sol (0.6, 0.4, 0.2), Mg-Sol+Cu (0.6/0.15, 0.4/0.1, 0.2/0.05), TMN 113 (0.6, 0.4, 0.2), TMN 113+Cu (0.6/0.15, 0.4/0.1, 0.2/0.05), TMN 113+Cu+Mg (0.6/0.15/0.15, 0.4/0.1/0.1, 0.2/0.05/0.05), Magnesium Nitrate (0.6, 0.4, 0.2), and an untreated control (0).

LC50 results: NAC-ZnO (0.6) – 12h, NAC-ZnO (0.4) – 24h, NAC-ZnO (0.2) – 48h, NAC-ZnO+Cu (0.2/0.05) – 12h, NAC-ZnS (0.6) – 48h, NAC-ZnS (0.4) – 48h, NAC-ZnS (0.2) – 48h, NAC-ZnS+Cu (0.2/0.04) – 48h, CR-41 (0.6) – 12h, CR-41 (0.4) – 12h, CR-41 (0.2) – 12h, Zinc Nitrate (0.6) – 12h, Zinc Nitrate (0.4) – 12h, Zinc Nitrate (0.2) – 12h, Copper Sulfate (0.05) – 24h, Kocide (0.4) – 12h, NAC (0.5) – 48h, NAC (1) – 48h, Mg-Sol (0.6) – 48h, Mg-Sol (0.4) – 48h, Mg-Sol (0.2) – 48h, Mg-Sol+Cu (0.6/0.15) – 48h, Mg-Sol+Cu (0.4/0.1) – 48h, Mg-Sol+Cu (0.2/0.05) – 48h, TMN113 (0.6) – 48h, TMN113 (0.4) – 48h, TMN113 (0.2) – 48h, TMN113+Cu (0.6/0.15) – 12h, TMN113+Cu (0.4/0.1) – 12h, TMN113+Cu (0.2/0.05) – 24h, TMN113+Cu+Mg (0.6/0.15/0.15) – 12h, TMN113+Cu+Mg (0.4/0.1/0.1) – 12h, TMN113+Cu+Mg (0.2/0.05/0.05) – 24h, Magnesium Nitrate (0.6) – 48h, Magnesium Nitrate (0.4) – 48h, Magnesium Nitrate (0.2) – 48h, and Untreated (0) – 48h.

Notable findings: NAC-ZnS, NAC control and Magnesium only treatments (Mg-Sol & Magnesium Nitrate) did well in terms of not killing and in some cases did better at keeping the fish active and alive over the course of the experiment compared to the untreated control. NAC-ZnS+Cu and Mg-Sol+Cu also did not kill the fish despite the addition of copper which is unexpected in the case of Mg-Sol+Cu due to the large amount of Cu present. Every time Cu was added in another treatment, such as NAC-ZnO, the respective LC50 dropped. Copper sulfate and Kocide controls exhibited high toxicity. TMN113 by itself performed much better when compared to industry controls ZnO CR-41 & Kocide 3000. NAC-ZnO (0.6) and all Zinc Nitrate treatments exhibited similar toxicity to Kocide 3000 and ZnO CR-41. Copper sulfate, even at such a low concentration (0.05) killed all fish after 24h, similar to TMN113+Cu. In the case of TMN113+Cu+Mg, all concentrations killed fish within 24h.

Your browser does not support pdfs, click here to download the file.