Effect of Bio-pesticides against Canola Flea Beetle, Phyllotreta cruciferae

Principle Investigator: Gadi V.P. Reddy

Project personnel: Frank Antwi, John H. Miller and Julie Prewett

Western Triangle Agricultural Research Center,

Montana State University,

9546 Old Shelby Rd.,

P.O. Box 656,

Conrad, MT 59425

Aim of the Study

The aim of this study was to compare the effect of bio-pesticides and traditional insecticides against canola flea beetle, Phyllotreta cruciferae.

Fig. Life cycle of canola flea beetle

Materials and Methods

Study sites

Field studies were conducted at two locations: Western Triangle Agricultural Research Center (WTARC) (48°18.627’N, 111°55.402’ W) in Conrad, and Sweet Grass (48°57.831’N, 111° 40.801’ W) Montana, USA. Seeding on experimental plots were done on 12 April, 2016 at WTARC, and on 13 April, 2016 at Sweet Grass. Canola seeds Hy-Class® (WindField Solutions, LLC) were used for both locations, and were seeded at a rate of 12 seeds per 30 cm using a four- row plot drill with a row spacing of 30 cm. The herbicide RT3® (a.i. glyphosate) at a rate of 2.5 L/ha was applied before seeding. At the time of seeding fertilizers at an N, P, K and S ratio of 134.5, 25.2, 61.6, and 22.4 kg/ha and N, P, K ratio of 12.3, 25.2, and 0 kg/ha were applied. The field trials were conducted under dryland (i.e., non-irrigated) conditions.

Treatments

The treatments used are as presented in Table 1. These were Water, Gaucho® (imidacloprid), Entrust® (spinosad), Steinernema-System® (Steinernema feltiae) + Barricade® (Barricade polymer 1%), Aza-Direct® (azadirachtin), Pyganic1.4® EC (pyrethrins), Grandevo® SC (Chromobacterium subtsugae), and Venerate® XC (Heat Killed Burkholderia sp. srain A396) as seed treatment and foliar application.

Plot design and data collection

The design for the field trial was a Randomized Complete Block Design (RCBD). The plot sizes used were 3.6 m × 1.2 m, and a buffer zone of 1.2 m was set up between each plot to avoid cross contamination of spray drift. Treatments were replicated 4 times at each location. A SOLO backpack sprayer (SOLO, Newport News, VA) calibrated at 816.89 L/ha was used for treatment application, after flea beetles arrival in plots and when air temperatures were (14 - 20 oC), and canola was in the cotyledon or one to two-leaf stage. Plots sprayed with water served as control. Each plot was rated for P. cruciferae feeding injury along one 3.6-m section of row, by sampling 10 plants at 0.3 m intervals before treatment applications (PT). The injury measurements of Phyllotreta cruciferae were made by visual classification into the EPPO damage categories as 1= no damage; 2 = up to 2% leaf area eaten; 3 = 3 - 10% leaf area eaten; 4 = 10 - 25% leaf area eaten; and 5 = >25% leaf area eaten (EPPO, 2004). The visual injury ratings were converted into percent leaf area injury with (OEPP/EPPO, 2004), where 1 = 0%; 2 = 2%; 3 = 5%; 4 = 10%; and 5 = 25% leaf area injury. Post-application ratings for P. cruciferae injury at 7 and 14 d after application of foliar insecticides (7 and 14 DPT) was used to determine treatment efficacy duration. Treatment effects were evaluated by comparing feeding injury and yield from plots.

Plots were swathed on 5 August, 2016 and harvesting was done on 16 August, 2016 at WTARC. At Sweet Grass the plots were straight combined on 1 September, 2016 when 50% of canola seeds were dark in color. The canola crop was harvested at 30% seed moisture, stored and air dried for 7 days until the seeds were at 8-10% moisture. The seeds were then cleaned and weighed to determine the seed yield per plot (as kilograms per hectare) for each experimental unit between August and October, 2016.

Data analysis

Data were analyzed using multivariate analyses of covariance (SAS Institute, 2015). This was done to account for and eliminate effects of pre-foliar treatment ratings on change in P. cruciferae feeding injury across dates after treatments. Least square means (LSMEANs) was run following ANOVA (SAS Institute, 2015). PROC GLM procedure (PROC GLM, SAS Institute 2015) was used in determining the main and interaction effects of location by treatment on P. cruciferae feeding injury ratings and yields.

Results

Leaf area feeding injury due to flea Phyllotreta cruciferae were generally lower for the chemical seed treatment Gaucho across the locations (Table 2). Leaf area feeding injury at pre-treatment (PT) ranged from 1.7 to 6.1% at WTARC (Table 2). At 7 days post treatment (7 DPT) Gaucho treatment resulted in a significantly lower leaf area injury of 5.4% (Table 2). The leaf area injury for the rest of the treatments were not significant when compared to the water control (Table 2). Except Gaucho, and Entrust which had lower leaf feeding injury of 7.6 and 8.6, respectively, none of the treatments had feeding injuries which were significant when compared to the water control (Table 2).

At Sweet Grass leaf area feeding injury by Phyllotreta cruciferae varied from 3.1 to 6.3% at PT (Table 2). At 7 DPT in Sweet Grass the trend in feeding injuries were similar to that of WTARC (Table 2). Gaucho was the only treatment that resulted in a significantly lower feeding injury of 6.6% at Sweet Grass (Table 2). Gaucho treatment resulted in a significantly leaf feeding area of 8.0% in Sweet Grass at 14 DPT (Table 2). Except Grandevo at 14 DPT, leaf area feeding injury for all the treatments were significant when compared to the water control in Sweet Grass (Table 2).

The yield (F = 12.36; df = 17,95; P < 0.0001) and location (F = 165.99; df = 1,95; P < 0.0001) effects were significant. However, treatment (F = 1.69; df = 8, 95; P = 0.1131), and location × treatment (F = 0.80; df = 8,95; P = 0.6006) effects were not significant.

Gaucho treatment resulted in a higher yield of 937.3 kg/ha at WTARC ((Table 3). However, none of the treatments had yield which were significant when compared to the water control (Table 3). Entrust (863.0 kg/ha) and Scanmask + Barricade (817.2 kg/ha) were the treatments that had a greater seed yield after Gaucho (Table 3). At Sweet Grass seed yield among the treatments were not significant (Table 3).

Seed test weight were not significant among the treatments at WTARC (Table 4). Seed test weight for Grandevo was higher (60.8 lb/bushel) at Sweet Grass (Table 4). However, except Grandevo test weight among the treatments were not significant when compared to the water control (Table 4).

References

OEPP/EPPO. 2004. Efficacy evaluation of insecticides. Phyllotreta spp. on rape, pp. 242-244. OEPP/EPPO Bull. Pp 1/218.

SAS Institute Inc. 2015. 9.4 In-Database Products, User’s Guide, fifth ed. SAS Publishers, Cary, NC, USA.

Acknowledgements

This work was supported by Montana Wheat and Barley Committee. This material is also based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Multistate Project W3185, The Working Group Biological Control of Pest Management Systems of Plants under Accession # 231844.

Table 1. Materials and rates of application in each treatment

Table 2. Crucifer flea beetle leaf area feeding injury to seedling canola treated with reduced risk insecticides in Montana

a, PT, pre foliar application.

b, 7 DPT, days after foliar application.

c, 14 DPT, days after foliar application.

WTARC: Hypothesis of no overall treatment effect (F=4.46; df =16, 938; P < 0.0001)

WTARC: Hypothesis of no overall pre-treatment leaf area effect (F = 2.10; df =2, 469; P = 0.1238)

Sweetgrass: Hypothesis of no overall treatment effect (F = 10.87; df =16, 938; P < 0.0001) Sweetgrass: Hypothesis of no overall pre-treatment leaf area effect (F = 3.76; df =2, 469; P = 0.0240)

Table 3. Canola seed yield after treatment of seedlings with reduced risk insecticides in Montana

a, WTARC, Western Triangle Agricultural Research Center.

Table 4. Canola seed test weight after treatment of seedlings with reduced risk insecticides in Montana

a, WTARC, Western Triangle Agricultural Research Center.