PCC MarchApril Final Draft

Continued from Page 31
study (Figure 2). The reduction in moth
populations from mating disruption was
significant on September 18 (P =0.039) and
October 15 (P = 0.006).
The mean number of larvae per 25 plants
in a replication was zero on all observation
dates except for 0.01 on Aug. 30 in the
plots that received CheckMate. Four insecticide
applications made by the time the
study was initiated and the remaining six
applications effectively suppressed larval
populations.
Larval feeding damage ratings were
consistently low (P < 0.0001) in the plants
that did not receive CheckMate DBM-F
(Figure 3). The damage was limited to the
older leaves at the bottom of the plants
and must have been from early feeding
before the initiation of the study. The lack
of larvae and the evidence of new feeding
damage also confirm that the crop remained
healthy and pest-free.
Yield and Cost Comparisons
Since frequent pesticide applications
effectively suppressed larval populations
and prevented their feeding damage, the
effectiveness of mating disruption on larval
populations or their damage could not
be determined in this study. Moths found
in the traps probably developed from the
larvae in the field or could have been those
that flew in from other areas.
However, lower moth populations in
CheckMate DBM-F treatment demonstrated
the overall influence of mating disruption
and pest suppression.
It is common to make about 10 to 12 pesticide
sprays during the six-month crop
cycle of Brussels sprouts. The cost of each
application varied from about $73 to $192
depending on the materials used with an
average cost of about $128 per application
in this study. The cost of two CheckMate
DBM-F applications is $91. If diamondback
moth populations could be reduced
with mating disruption, it is estimated
that two to three pesticide applications
could be eliminated. That results in $164
to $292 of saving for the pesticide costs
and additional savings in the application
Continued on Page 34
Number of moths/traps
Damage Rating
300
250
200
150
100
50
0
1.5
1.0
0.5
0.0
8/8/2020
8/20/2020
8/30/2020
P < 0.0001
Diamondback Moth Occurrence
Grower Standard
9/1/2020
9/11/2020
Larval Feeding Damage
Grower Standard
9/18/2020
10/6/2020
P < 0.0001
Figure 3. Feeding damage by diamondback moth larvae.
GS+CheckMate
9/27/2020
Figure 1. Mean number of diamondback moth adults found in the traps.
20.00
0.00
-20.00
-40.00
-60.00
-80.00
-100.00
8/8/2020
GS+CheckMate
10/6/2020
% Control from CheckMate DBM-F
8/20/2020
9/1/2020
9/11/2020
9/18/2020
9/27/2020
10/6/2020
10/18/2020
P = 0.0074
10/15/2020
10/15/2020
Figure 2. Reduction in moth populations by adding pheromone for mating disruption.
32 Progressive Crop Consultant March / April 2021