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2000 Insecticide Efficacy Trials
Flea Beetle Management on Canola

Janet J. Knodel and Mark Halvorson
Crop Protection Specialist and Agronomist

Introduction
Canola, Brassica napus L., is a high quality edible oil crop. Flea beetles are the primary insect pest of canola in the Northern Great Plains, capable of eliminating seedling stands or in less severe cases, reducing yield and seed quality.   Currently, the most effective management measure is the use of insecticides for managing the overwintering generation of flea beetles that emerges 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. Data were collected on the efficacy of different seed treatments and foliar applied insecticides.

Material and Methods
Brassica napus cv. Minot RR was seeded on May 9, 2000 at 8 lbs. of live seed per acre. Due to the poor emergence of the first planting, the trial was replanted on May 25, 2000. Treatments were arranged in a randomized complete block design with four replicates per treatment. Experimental units were 3.5 ft. (7 rows) x 20 ft. The following 18 insecticides listed in Table 1 were evaluated for crucifer flea beetle management on canola during 2000. This included 10 seed treatments and eight foliar application.

All foliar insecticides were applied during the early evening on June 9, 2000, 15 days after second planting, using a CO₂ back pack sprayer. The application rate was 10 gal / A using 40 psi and TJ 8001 nozzles. Spray applications were not initiated until the economic threshold of 25% foliar damage was reached in the plots. The canola was in the cotyledon to the 2-leaf stage.

Flea beetle populations were monitored weekly using sticky yellow trap cards. Unfortunately, this trial also had poor weed control with a heavy density of shepherd’s purse throughout the plots. Due to rainy weather, the plots were sprayed late with Roundup. Roundup (1 pt./A) + AMS was finally applied on June 3, 2000 for weed control. Since the canola seedlings were under severe competition from the shepherd’s purse, a decision was made not to conduct a detailed flea beetle assessment with other factors affecting the canola growth. As a result, the percent incidence of plants damaged by flea beetles and a general damage rating were used to assess flea beetle damage in only the second planting.

1)     Percent Incidence: Counting the total number of plants in a 16 ft. long section of row, and then recounting the number of plants with flea beetle damage determined the percent incidence. Any plant with pitting or other feeding punctures was considered damaged. This also provided the plant stand count (# plants/sq. foot).

2)     Damage Rating: Each plot was rating on August 11, 2000 with 1 being the “worst” (untreated check) and 4 being the “best."

Table 1. Chemical Treatments Tested Against Flea Beetle.
Treatment	Formulation	Product Rate
Untreated check
FOLIAR SPRAYS
Asana (Dupont)	0.66 EC	3.9 fl oz/A 7.8 fl oz/A
Capture (FMC)	2 EC + 17.7 FS	1.3 fl oz/A 2.1 fl oz/A
Warrior T (Zeneca)	1 CS	0.96 fl oz/A 1.28 fl oz/A
MP062 + Spreader/sticker (Dupont)	1.25 SC	5.6 fl oz/A + 0.5% V/V
SEED TREATMENTS
Helix (Adage + Apron XL, Maxim, Dividend) (Novartis)	34 FS	23 fl oz/cwt
Lindane (AGSCO)	ST 40	43 fl oz/cwt
Carboxin-thiram + Allegiance (Gustafson) GUS #1	FL	9 fl oz/cwt + 0.5 fl oz/cwt
Carboxin-thiram + Allegiance + Gaucho 600 (Gustafson) GUS #2	FL FS	9 fl oz/cwt + 0.5 fl oz/cwt 10.25 fl oz/cwt
Carboxin-thiram + Allegiance + Gaucho 600 (Gustafson) GUS #3	FL FS	9 fl oz/ cwt + 0.5 fl oz/cwt 20.5 fl oz./cwt
Carboxin-thiram + Allegiance + Gaucho 600 (Gustafson) GUS #4	FL FS	9 fl oz/ cwt + 0.8 fl oz/cwt 20.5 fl oz/cwt
Carboxin-thiram + Allegiance + GUS #5 (Gustafson)	FL	9 fl oz/cwt cwt + 0.5 fl oz/cwt --
Carboxin-thiram + Allegiance + GUS #6 (Gustafson)	FL	9 fl oz/cwt cwt + 0.5 fl oz/cwt --
Benlate + Gaucho 600(Gustafson) GUS #7	50 WP FS	8 fl oz/cwt 12.8 fl oz/cwt
GUS #8 (Gustafson)	--	--

Canola plots were swathed on August 14, 2000 and harvested on August 25, 2000. The following data were collected from each plot: yield (lbs./acre), test weight (lbs/bushel), seed weight (g/1000 seeds), and percent oil.

Data were analyzed using SAS ANOVA procedure and LSD test.

Results and Discussion

Population Dynamics of the Crucifer Flea Beetle:
During 2000, the flea beetle activity started mid-May and continued until early July (Fig. 1). The numbers of flea beetles at Minot had a high average trap catch of 923 beetles per trap week during the peak activity between June 25 and July 3. The duration of the feeding period was approximately 1.5 months long. In 1999, the population trends were similar - started to increase in late May and continue for a month long (Fig. 1). However, the numbers were lower with an average trap catch of 290 beetles per trap week during peak activity. The majority of the canola crop was planted in the North Central Region during early-mid May, which provided opportune time for the emerging flea beetles to infest. Unfortunately, some canola fields had to be rescued with one or more applications of a foliar insecticide regardless of whether the seed was treated or not.

Flea Beetle Damage Assessments: (Table 2 & 3)
The treatments with the highest plant per square foot are GUS #3, Helix, Gus #1, Gus #4, and MP062. The seed treatments generally had a higher plant stand count, average of 9.1 plants per square foot compared to the foliar applied insecticides of 7.1 plants per square foot. This suggests that the seed treatment may improve seedling emergence. It is also interesting to note that the fungicide alone treatment (GUS #1) had one of the higher plant stand counts. This suggests that the fungicide part of a seed treatment may be more important in preventing soil borne diseases from inhibiting emergence. Most treatments were not significantly different from each other, except for the highest counts from the lowest counts (see Table 2).
The average percent incidence among treatments was high, 66.8%, indicating heavy flea beetle pressures at the time of canola emergence. No major trends could be detected among the treatments. Generally, seed treatments had a slightly lower percent incidence, average of 66.9%, compared to the foliar applied insecticide, average of 73.8%, but this difference was not significant. The untreated check had one of the highest percent incidences, 81%, as expected.

Table 2. Flea Beetle Damage Assessment and Harvest Data from Second Planting.
Treatment	Plant Stand Plants/ sq. foot	% Incidence	Damage Rating	Yield lb/A	Test Weight lb/Bushel	% Oil	Seed Weight g/1000 seeds
Untreated check	6.0 cd	81.0 a	2.7 f	1048 e	50.4 cde	45.1 abc	2.8 abc
Asana 3.9	5.8 cd	79.7 abc	3.0 def	1361 bcde	50.3 e	45.3 abc	2.8 abc
Asana 7.8	7.3 abcd	65.9 abcde	3.0 def	1315 de	50.6 abcde	44.6 bc	2.8 abc
MP062	9.8 abcd	63.9 abcde	3.0 def	1327 cde	50.5 bcde	45.3 abc	2.8 abc
Capture 1.3	6.9 bcd	46.2 e	3.2 bcdef	1354 cde	50.6 abcd	45.6 abc	2.7 bc
Capture 2.1	5.3 d	74.9 abcd	3.5 abcd	1440 abcd	50.5 bcde	46.2 a	2.8 abc
Warrior 0.96	7.6 abcd	61.2 bcde	3.3 abcdef	1348 cde	50.3 de	45.6 abc	2.9 ab
Warrior 2.6	7.1 abcd	56.9 de	3.1 cdef	1545 abcd	50.6 abcd	45.8 ab	2.8 abc
Lindane	6.8 bcd	67.9 abcd	2.8 ef	1116 e	50.7 abc	44.5 bc	2.7 c
GUS #1 Fungicide alone	10.9 abc	71.1 abcd	2.8 f	1266 de	50.6 abcde	44.9 abc	2.8 abc
GUS #2 Gaucho 600	9.0 abcd	54.9 de	2.8 f	1390 bcde	50.7 abcd	45.2 abc	2.8 abc
GUS #3 Gaucho 600	12.5 a	67.7 abcd	3.6 abcd	1720 abc	50.6 abcde	46.0 ab	2.8 abc
GUS #4 Gaucho 600	10.1 abcd	59.7 cde	3.6 abcd	1642 abcd	50.6 abcde	45.9 ab	2.8 abc
Gustafson #5	7.1 bcd	63.1 abcde	3.8 abc	1640 abcd	50.7 abc	46.1 ab	2.8 abc
Gustafson #6	8.6 abcd	65.9 abcde	3.9 a	1759 ab	50.8 ab	45.5 abc	2.9 ab
GUS #7 Benlate + Gaucho 600	8.2 abcd	82.8 a	2.7 f	1081 e	50.9 a	44.0 c	2.7 c
Gustafson #8	6.3 cd	68.9 abcd	3.2 bcdef	1332 cde	50.6 abcde	45.6 abc	2.8 abc
Helix	11.9 ab	71.3

FOLIAR SPRAYS

SEED TREATMENTS