ontario sugar beet growers - Atrium - University of Guelph

CROP:
PEST:
Sugar beet (Beta vulgaris L.) cv. El7
Rhizoctonia Crown Rot, Rhizoctonia solani Kuhn
Cercospora leafspot, Cercospora beticola, Sacc.
NAME AND AGENCY:
PITBLADO, R E
Ridgetown College; University of Guelph, Ridgetown, Ontario, NOP 2C0
Tel: (5 19) 674-1 605 Fax: (5 19) 674-1600 E-mail: mitblad@,ridgetownc.uoguelph.ca
TITLE:
CONTROL OF RHIZOCTONIA CROWN ROT IN SUGARBEETS- NON-
ARTIFICIALLY INOCULATED PLOT- 2005
MATERIALS: HEADLINE 250EC (pyraclostrobin), QUADRIS 250SC (azoxystrobin).
METHODS: Sugarbeets were planted at the research station in Ridgetown, on May 6,2005. Plots were
two rows, 7 m in length spaced 0.75 cm apart, replicated four times in a randomized complete block
design. The location chosen had not had sugarbeets grown on it for at least two years (cabbage was
grown for the 2 years prior to this tial) and the plot was not artificially infected with Rhizoctonia
inoculum. The in-furrow spray applications were directed over the seed and then covered on May 7 using
a specialized small plot research CO, sprayer with a single nozzled hand-held boom applying 200Lha of
spray mixture. The at emergence sprays were applied over the planted row in a 15 cm band on May 26
and at the 4-leaf stage on June 9. Assessments were conducted by giving a plant vigour rating on July 15
and counting the number of dead plants cause by infection by Rhizoctonia crown rot. In addition the plots
were rated for the number of infection sites caused by Cercospora Leafspot disease on September 12.
Results were analysed using the Duncan's multiple range test (PI 0.05).
RESULTS: Data are presented in Table 1.
CONCLUSIONS: The vigour ratings improved for the non in-furrow treated plots in this trial where the
plots did not have any additional Rhizoctonia crown rot disease inoculum to deal with compared to Trial
2 which contained a similar treatment list but had been artificially inoculated. The question was then was
whether or not the lack of vigour and seedling emergence in that tial was due to the method of applying
the chemicals as an in-furrow treatment. It appears that in this trial the technique of applying the infurrow
treatments did not give any advantage to emergence or plant vigour and thus one should conclude
that in tial2 the benefits shown in the in-furrow treatments was due to its ability to control Rhizoctonia
crown rot infections at this early stage.
In this tial there was very little disease pressure with few plants dying as a result of infections by
Rhizoctonia. It should also be noted that the treatments for the control of Rhizoctonia crown rot did not
persist long enough to affect the leafspot disease caused by Cercospora.