Reduced Seed Treatment Inputs for Management of Crucifer Flea Beetle, Phyllotreta cruciferae Goeze,

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Reduced Seed Treatment Inputs for Management of
Crucifer Flea Beetle, Phyllotreta cruciferae
(Goeze), in Canola
Denise L. Olson, Janet J. Knodel, Robert Henson,
and Bryan Hanson North Dakota State University
ABSTRACT
RESULTS
Crucifer flea beetle, Phyllotreta cruciferae
(Goeze), is an economic pest of seedling canola.
Canola is an important crop of North Dakota
agriculture and it is becoming expensive to
produce due to the high input costs of
pesticides, seed, and fertilizer. The efficacy
and agronomic performance of using reduced
proportions of insecticide-treated canola seed
was compared using commercially available seed
treatments at their low and high rates. Four
different proportions of treated seed were
evaluated 0, 33, 67, and 100 treated seed. The
results from six site years indicate that flea
beetle feeding injury to seedling canola is
inversely related to the proportion of treated
seed. The 100, 67, 33, and 0 treated seed
treatments had an average injury rating of 3.2,
3.6, 4.0, 5.0, respectively, across site years.
Yield was generally higher for the 100 treated
seed and decreased proportionally as the
percentage of treated seed declined regardless of
the insecticide treatment. This research
indicates that the proportion of treated seed at
the high or low rates of insecticide seed
treatment can influence flea beetle control, and
agronomic crop performance of canola.
Spring Flea Beetle Populations Crucifer flea
beetle spring emergence was delayed until mid- to
late May during both experimental years due to
the cool, wet conditions (Fig 1). Flea beetle
spring emergence continued until late June. In
2003, beetle populations peaked in mid- to late
May at Minot and Langdon, and in mid-June at
Carrington. The flea beetle populations were
reduced in 2004, possibly due to greater
overwintering mortality. Crucifer Flea Beetle
Feeding Injury Table 2 In 2003 at Minot, all of
the treatments had a significantly lower flea
beetle injury rating than the untreated check.
In general, the 100 Helix XTra and 100 Prosper
400 had significantly lower injury ratings than
the treatments of reduced proportions of treated
seed. As the percent of treated seed decreased,
the injury ratings increased. For example, on 38
DAP, the high rate of the seed treatments at 100
treated seed had an average feeding injury rating
of 1.5, 2.6 for 67, and 3.2 for 33. At
Langdon, only 100 and 67 Helix XTra treated
seed had a significantly lower injury rating than
the untreated check. At Carrington only the 100
and 67 treated seed of Helix XTra had
significantly lower feeding injury compared to
the untreated check. Across the locations, the
high rate of seed treatments usually had less
feeding injury at 100 treated seed compared to
67 and 33, although these differences were not
always significant. Table 3 In 2004 at Minot,
all of the insecticide treatments had a
significantly lower flea beetle injury rating at
34 DAP than the untreated check. Although the
100 treated seed usually had lower injury
ratings than the 67 and 33 treated seed, these
differences were not always statistically
significant. At Langdon, the insecticide
treatments at 100 treated seed, 67 Helix XTra,
67 Prosper 400, 33 Helix Lite, and 33 Prosper
400 had significantly lower flea beetle injury
ratings than the untreated check at 34 DAP. The
high rate of the seed treatments at 100 treated
seed had significantly lower injury ratings
compared to most other seed treatments at lower
proportions of treated seed. At Carrington, all
of the 100 treated seed treatments (except 100
Prosper 200), 67 Helix XTra, and 67 Prosper 400
had significantly lower injury ratings than the
untreated check at 34 DAP. Again, the high rate
of the seed treatments at 100 treated seed had
significantly lower injury ratings compared to
other seed treatments at lower proportions of
treated seed. Canola Yields Table 2 In 2003
at Minot, the insecticide seed treatments had
significantly higher yields than the untreated
check, except 33 Helix lite, 33 Prosper 200,
and 67 Prosper 200. At Langdon, the high rate
seed treatments at 100 and 67 treated seed had
significantly higher yields than the untreated
check. At Carrington, only 100 Helix XTra had a
significantly higher yield than the untreated
check. The 100 Helix XTra had a significantly
higher yield compared to all other seed
treatments, expect 100 Prosper 400. At all
experimental sites, the treatments with the high
rate of insecticide seed treatments and 100
treated seed, had the highest yields. Table
3 Canola yields were not significantly different
among the experimental treatments at Minot in
2004. At Langdon, the following treatments had a
significantly higher yield than the untreated
check (ranked from highest to lowest) 100 Helix
Lite, 100 Helix XTra, 33 Prosper 400, 67 Helix
XTra, 33 Helix XTra, and 67 Helix Lite. At
Carrington, 100 Helix XTra, 100 Prosper 400,
100 Helix Lite, 67 Helix XTra and 33 Prosper
400 had significantly higher yields than the
untreated check. Across the proportions of
treated seed, 67 and 100 treated seed had
higher yields than 33 treated seed and the
untreated check. There were no significant
differences in yield among seed treatment
products at Minot and Carrington.
INTRODUCTION
Canola oil is expanding its market share due to
its placement as one of the healthiest of
vegetable oils. The high market demand for
canola makes it an increasingly important crop
for growers in North Dakota. Canola adds
diversity to crop rotation systems and provides
an important cash crop to central, north central
and northeastern North Dakota. North Dakota
produces 85 of US canola and production has had
an average annual value of 122 M during the
recent eight years. The crucifer flea beetle,
Phyllotreta cruciferae Goeze, represents a major
insect pest to canola production in the Northern
Great Plains. Flea beetles can invade and reduce
newly emerged plant stands within a few days.
Currently, the most effective management
technique is the use of insecticides to control
the overwintering generation of flea beetles that
emerge early in the spring. The seedling stage
is the most critical period and insecticides
often need to be applied as a seed treatment or
as a foliar application to protect the crop from
flea beetle damage. A Post-emergence foliar
insecticide requires a timely application within
a small window of opportunity. Therefore, seed
treatments are obviously more convenient and
commonly used. Canola is expensive to produce
due to the high input costs of pesticides, seed
and fertilizer. Across different canola growing
regions of North Dakota, canola has an estimated
input cost of 58.53 per acre, compared to oil
sunflowers at 35.55 per acre and hard red spring
wheat at 32.70 per acre. In general, canola
growers must plan for about 20 per acre higher
expenses than other crops. The objective of this
research was to determine if the insecticide seed
treatment cost (7.00 per acre) can be reduced
while maintaining effective control of the
crucifer flea beetle in areas with different
population pressures. This has never been tested
before in North Dakota and would result in lower
input costs as well as reducing the risk of
insecticide contamination in the soil.
MATERIALS AND METHODS
Experimental Treatments Three ratios of
insecticide treated seed using two commercial
seed treatments, at their low and high rates,
were evaluated for a total of 13 treatments
(Table 1). Experimental Years 2003 and
2004. Experimental Sites North Dakota State
University Experiment Station Research Extension
Centers in north central (Minot), north east
(Langdon), and central (Carrington) North
Dakota. Experimental Establishment Brassica
napus, open pollinated cv. RaiderRR (Integra Seed
Ltd) 151-183 pure live seeds/m2 early to
mid-May. Experimental Plots 1.07-1.25 m wide (7
rows) x 6.1-7.6 m long equal size buffer plot of
canola between each treatment plot. Treatment
Assessments Flea beetle feeding injury ratings
at approximately 25, 31, 38, and 45 days after
planting (DAP) on 10 plants along a 4.9 m row
section using the following rating scheme 1
0-3 pits, 2 4-9, 3 10-15, 4 16-25, 5 gt25
pits per seedling, and 6 dead seedling Harvest
data Yield (kg/ha).
DISCUSSION
This research has shown that 100 treated seed
and the high rate of insecticide seed treatments
are crucial for protecting seedling canola
against flea beetle feeding injury and subsequent
economic yield losses in areas where the beetle
populations are moderate to high. The 100
treated seed had an average injury rating of 2.9,
67 treated seed had 3.1, 33 treated seed had
3.7, and the untreated check had 4.6. The high
rate of insecticide seed treatments had a lower
injury rating of 3.1 compared to the injury
rating of 3.4 for the low rate of insecticide
seed treatments. Yield was generally higher
for the 100 treated seed and yield decreased
proportionally as the proportion of treated seed
declined regardless of the insecticide. Use of
an insecticide seed treatment affected yield more
than which product was used. In addition, the
higher rates of insecticide seed treatment
products generally had a higher yield than the
lower rates.
In memory of our colleague, Robert Henson, who
was essential to the completion of this research.