Agricultural Research Division of IANR
Date of this Version
2014
Citation
Phytopathology 103:1235-1242.
Abstract
Potato zebra chip (ZC), caused by the bacterial pathogen ‘Candidatus
Liberibacter solanacearum’, which is vectored by the potato psyllid
(Bactericera cockerelli), has caused widespread damage to U.S. potato
production ever since its first discovery in south Texas in 2000. To
determine the influence of environmental factors and management
practices on ZC occurrence, data on management and meteorological
variables, field locations, and psyllid counts were collected over a 3-year
period (2010 to 2012) from six locations across the central United States
(south Texas to Nebraska). At these locations, ZC-symptomatic plants
were counted in 26 fields from systematically established 20 m × 30 m
plots around the field edges and field interiors. Mean numbers of symptomatic
plants per plot were classified into two intensity classes (ZC ≤ 3
or ZC > 3) and subjected to discriminant function and logistic regression
analyses to determine which factors best distinguish between the two ZC
intensity classes. Of all the variables, location, planting date, and maximum
temperature were found to be the most important in distinguishing
between ZC intensity classes. These variables correctly classified 88.5%
of the fields into either of the two ZC-intensity classes. Logistic regression
analysis of the individual variables showed that location accounted
for 90% of the variations, followed by planting date (86%) and maximum
temperature (70%). There was a low but significant (r = –0.44983, P =
0.0211) negative correlation between counts of psyllids testing positive
for pathogen and latitudinal locations, indicating a south-to-north declining
trend in counts of psyllids testing positive for the pathogen. A
similar declining trend also was observed in ZC occurrence (r = –0.499,
P = 0.0094).
Comments
U.S. Government Work