Active for Control of Aphids in Laboratory Trials. Ed King, Mary Kubiszak and Luis E. Gomez, Crop Protection R&D, Dow AgroSciences, Indianapolis, IN. Abstract.
TM
Influence of pH and Temperature on Isoclast
Active for Control of Aphids in Laboratory Trials
Ed King, Mary Kubiszak and Luis E. Gomez, Crop Protection R&D, Dow AgroSciences, Indianapolis, IN Abstract IsoclastTM active (sulfoxaflor) is the first member of the novel sulfoximine class of insecticides, developed for management of sap-feeding insect pests. It controls insect pests via a unique interaction with the insect nicotinic acetylcholine receptor and has a broad lack of cross-resistance to other insecticides. Research has been conducted at Dow AgroSciences for several years to characterize the performance of Isoclast active formulations under different conditions for control of sap-feeding insect pests. This poster summarizes a series of laboratory studies that examined the effects of temperature and pH spray solution on Isoclast active for control of aphids. Results showed Isoclast active to provide robust control of aphids under a wide range of temperature and pH. Isoclast is sold in the United States as Transform™, Closer® and Sequoia™ Insecticides.
Methods and Materials
Cotton Aphid Temperature Test
Methods Common To All Trials • Application: Insecticides were applied to seedling plants (1-leaf cotton or 2-3 leaf cabbage) using Mandel Track Sprayer @ 400L/Ha total spray volume. • Infestation: Infested 2-3 hours after spray dried with 25-30 aphids per cotton leaf; also infested 1 & 4 DAT in UV Aging study. • Evaluation: Plants were held for 3 days and graded by counting the number of live aphids on each leaf. • Replications: Temperature test conducted twice (6 replicates per test); pH tests replicated 4 times. • Statistics: Aphid counts used to calculate percent control on an Abott’s corrected basis, using control treatment live counts. Analysis of variance (ANOVA) statistical procedures was applied on aphid counts, and Tukey-Kramer HSD was used as the mean separation test (p = 0.05). Log-Probit analysis of data was also used to generate LC50/90 values at each temperature (for both ppm and converted g ai/ha). JMP® statistics software was used for statistical analysis of data (SAS Institute, Inc).
Figure 1. Effect of Temperature on Efficacy of Isoclast Active vs. Cotton Aphids
% Corrected Control
Cotton Aphid, Aphis gossypii (Cotton): Effects of Temperature on Dose Response • Formulation and Rates (ppm): 11.43% Isoclast SC formulation tested at 50, 25, 12.5, 6.25, 3.12, 1.56, 0.78, and 0.39 ppm. Spray adjuvant (0.03% X-77) was used for each spray dilution. Water with adjuvant used as the control. • Holding Conditions: Plants were placed in a controlled environmental chamber (16 L: 8D) at one of three constant temperatures: 13o, 25o, or 34o C. Green Peach Aphid, Myzus persicae (Cabbage): Effects of pH on Dose Response • Formulation, Rates (ppm) and pH Levels: 24% Isoclast SC, and 17.6% imidacloprid SC were tested at 100, 25, 12.5, 6.25, 1.56, 0.78, and 0.39 ppm. Each pesticide formulation was diluted in buffer solutions with ph levels of 4, 7 or 10. Spray adjuvant (0.03% X-77) was used for each spray dilution. Untreated buffers with adjuvant used as the control. • Holding Conditions: Plants were placed in a controlled environmental chamber and standard lighting (16 L: 8D) at 26o C. Green Peach & Cotton Aphid: Effects of pH on UV Residual Efficacy • Formulation, Rates (ppm) and pH Levels: 24% Isoclast SC, 17.6% imidacloprid SC, and 50% flonicamid WDG were tested at 62.5 ppm. Each pesticide formulation was diluted in buffer solutions with ph levels of 4, 7 or 10. Spray adjuvant (0.03% X-77) was used for each spray dilution. Untreated buffers with adjuvant used as the control. • Holding and UV Aging: Plants were infested 2-3 hrs after spray, other aging groups also held for 1-day or 4-days under UV light (16L: 8D) at 26o C before infesting.
Isoclast
Imidacloprid
Imidacloprid
0.70 3.63 3.18 27.45 4 (0.1-1.9) (1.0-9.5) (1.0-7.31) (10.4-173) 0.74 1.18 4.53 5.71 7 (0.3-1.4) (0.7-1.7) (2.5-7.8) (4.1-7.9) 0.41 0.43 2.90 2.42 10 (0.2-0.7) (0.01-1.7) (2.0-4.0) (0.3-7.9) LC values with overlapping CI’s are not significantly different.
Isoclast Imidacloprid
4
7
pH of Spray Solution
10
• The rate response for Isoclast active was consistent at each pH, and there were no significant differences in LC50 and LC90 values between different pH levels (Table 2). High levels of control at labeled rate range (Figure 2). • At same rates, imidacloprid was less robust than Isoclast when tested at pH 4 (Table 2 & Figure 2). Imidacloprid provided highest level of activity at pH 10 and lowest activity at pH 4. • In summary, Isoclast active showed consistent activity across pH levels tested in this study. ®™Trademark of the Dow Chemical Company (“Dow”) or an affiliated company of Dow. Isoclast is not registered for sale or use in all countries or states. Always read and follow label directions.
95% CI
13°
1.35
0.9-2.3
10.40
5.3-31.9
25°
0.15
0.002-0.5
0.93
0.3-7.8
34°
< 0.08
NA
0.09
0.002-0.3
Within each LC column, values with overlapping CI’s are not significantly different.
Rate (ppm) 25
50
Figure 3. Green Peach Aphid, Data Averaged Across UV Aging Periods (0, 1 & 4 Days). Test rate of 62.5 ppm (= 25 g ai/ha) 90 80 70 60 50 40 30 20 10 0
Isoclast Imidacloprid
4
7 pH of Spray Solution
10
Figure 4. Cotton Aphid, Data Averaged Across UV Aging Periods (0, 1 & 4 Days). Test rate of 62.5 ppm (= 25 g ai/ha)
% Corrected Control
Isoclast
13 C 25 C 34 C
LC90 (g ai/ha)
• Potency of Isoclast active increased with rise in temperature (Figure 1 and Table 1). • Results under higher temperature conditions are reflective of the excellent efficacy reported for Isoclast active formulations in field trials. During periods of cool temperatures, the data indicates slower activity or reduced efficacy; although a highly significant level of control could still be achieved with recommended labeled use rates (e.g., 25 g ai/ha).
% Corrected Control
PPM LC90 Values (95% CL)
% Corrected Control
ph
PPM LC50 Values (95% CL)
Temperature
95% CI
Effect of pH On UV Aging Residual Efficacy (Green Peach & Cotton Aphid)
Figure 2. Efficacy, Averaged Across 3 Highest Rates (6.25 -100 ppm = 2.5-40 g ai/ha) 100 90 80 70 60 50 40 30 20 10 0
Temp (C) LC50 (g ai/ha)
0.39 0.78 1.56 3.12 6.25 12.5
Green Peach Aphid Test (Cabbage), Effect of pH On Dose Response
Table 2. Dose Response (ppm) of Insecticides Applied With 3 Different pH Solutions on Cabbage (Green Peach Aphid)
Table 1. Temperature Effect on Dose Response (converted to g ai/ha) of Isoclast Active, Cotton Aphid
100 90 80 70 60 50 40 30 20 10 0
90 80 70 60 50 40 30 20 10 0
Isoclast Flonicamid
4
7
10
pH of Spray Solution
• Green Peach Aphid: Isoclast provided significantly (p = 0.05) better control than imidacloprid at pH 4 & 7 (Figure 3). Formulations statistically equal at pH 10. No significant effect (p =0.05) of pH on Isoclast. • Cotton Aphid: No statistically significant (p=0.05) effect of pH on Isoclast active or flonicamid (Figure 4). Overall, Isoclast active provided higher residual efficacy than flonicamid at this test rate. • Isoclast active gave highest levels of residual control at pH 7, but overall results show good stability in more extreme pH conditions.
