|Parker, P. E.|
|Bock, C. H.|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2005
Publication Date: 12/1/2005
Citation: Parker, P., Bock, C., Gottwald, T.R. 2005. Comparison of techniques to sample citrus canker bacteria (xanthomonus axonopodis pv. citri) in wind-blown spray. Plant Disease. 89:1324-1330. Interpretive Summary: Citrus canker is an economically important disease and is the target of an eradication program in south Florida. Little is known about the physical and biological processes of dispersal, deposition and infection. This information is important to our understanding of the epidemiology of the disease, to the eradication program and for the future management of the disease. This paper reports on the results of some experiments that were done to compare a number of different sampling apparatus to investigate which were most suited to sampling bacteria of citrus canker in wind-blown spray. The results showed that the PAS450 collected no detectable sample, the Burkard cyclone consistently collected spray, but was found to be less effective than panels or funnels, which collected the greatest volume of splash. Panels sampled the greatest volume, and effectively collected bacteria-laden wind-blown splash. Greater sampling area of the panels allowed a more representative sample compared to other methods tested. Panels or funnels are likely better methods to sample wind-blown spray compared to the two volumetric sampler types used. Panels and funnels are being used to investigate the dispersal of bacteria of citrus canker.
Technical Abstract: Four techniques were evaluated to sample wind-blown splash from canker-infected citrus plants. Two volumetric cyclone samplers (PAS450 and Burkard Cyclone) and two passive samplers (funnels and panels) were evaluated. The PAS450 collected no detectable sample in any trial. The Burkard cyclone consistently collected spray, but was found to do so even when powered off. Thus the Burkard cyclone essentially functioned passively negating the advantage of a volumetric sampler for this kind of sampling. Panels collected the greatest volume of splash followed by funnel traps. Colony forming units (CFU) of bacteria per ml collected was significantly different between Burkards and panel samplers, but panels and funnels collected similar concentrations (Burkards, funnels and panels collected 1182, 1426 and 2667 CFU of bacteria per ml, respectively). Positive correlations were found between the volume collected and the total bacteria collected, and between CFU of bacteria per ml and total bacteria sampled for panel and funnel samples, but there was no correlation between CFU of bacteria per ml and volume sampled for either sampler. The Burkard sample showed a strong positive correlation (P>0.01) between volume sampled, the total quantity of bacteria sampled and CFU of bacteria per ml. The CFU per ml collected by the panels and funnels were more similar (coefficient of determination, R2=0.97) compared to the relationship between the Burkard and panel catches (R2=0.68), or compared to the relationship between the Burkard and funnel catch (R2=0.62) catches. Panels sampled the greatest volume, and effectively collected bacteria-laden wind-blown splash. Greater sampling area of the panels allowed a more representative sample compared to other methods tested.