Managing Carzol^® for Maximum efficacy

against thrips - 2007

Lynn Jensen

Malheur County Extension Service

Clinton Shock and Lamont Saunders

Malheur Experiment Station

Oregon State University

Ontario, OR

Objective

Our objective was to determine the most effective rates and combinations of insecticides to use with Carzol SP^® to provide season-long thrips control and reduce the risk of resistance development. Not all insecticides referred to in this report are registered for use on onions. Always obtain and read the insecticide label to ensure that the product is registered for the crop for which it is intended.

Introduction

Oregon State University trials in 2005 showed that Carzol SP was effective in controlling thrips and reducing iris yellow spot virus (IYSV) incidence. The Environmental Protection Agency granted several states a Section 18 registration for Carzol SP use on onions for the 2006 and 2007 growing seasons, but at a lower rate than was considered effective. This project was designed to determine the optimum rate, timing, and rotation sequence with other insecticides to maximize thrips control within the parameters of the Section 18 label. The current label restricts the grower to a total of 24 oz/acre, with a maximum single application up to 20 oz.

Materials and Methods

Two trials were established at the OSU Malheur Experiment Station, one to look at the effectiveness of Carzol SP applied at different rates and spray intervals, the other to determine the most effective insecticides to rotate with Carzol SP in a complete thrips control program. The Carzol SP spray interval trial consisted of an untreated control and Carzol SP rates of 8, 12, 16, and 20 oz/acre, with application intervals of 1, 2, 3, and 4 weeks. The Carzol SP rotation trial consisted of 18 treatments of Carzol SP rotated with other insecticides (Table 1).

Table 1. Carzol SP rotation trial, insecticide treatments applied during the growing season, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Application

Application

Application

Application

Application

Application

Application

29-May

Rate/acre

8-Jun

Rate/acre

13-Jun

Rate/acre

20-Jun

Rate/acre

27-Jun

Rate/acre

3-Jul

Rate/acre

12-Jul

Rate/acre

1

UTCa

UTC

UTC

UTC

UTC

UTC

UTC

2

Carzol

8.0 oz

Carzol

8.0 oz

Carzol

8.0 oz

Carzol

8.0 oz

3

Lannate

3.0 pt

Carzol

16.0 oz

Lannate

3.0 pt

Carzol

16.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

4b

UTC

UTC

UTC

UTC

UTC

UTC

UTC

5

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

MSR

3.0 pt

MSR

3.0 pt

6

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

MSR

3.0 pt

Warrior

3.84 oz

Warrior

3.84 oz

MSR

3.0 pt

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

7b

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

MSR

3.0 pt

MSR

3.0 pt

8b

Success

6.0 oz

Success

6.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

Carzol

16.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

AzaDirect

16.0 oz

AzaDirect

16.0 oz

9c

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

10

Diazinon

1.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Carzol

20.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

MSR

3.0 pt

11

Success

6.0 oz

Success

6.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

Carzol

16.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

AzaDirect

16.0 oz

AzaDirect

16.0 oz

12

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

Lannate

3.0 pt

Carzol

16.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

MSR

3.0 pt

MSR

3.0 pt

MSR

3.0 pt

13

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

14

Success

6.0 oz

Success

6.0 oz

Success

6.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

AzaDirect

16.0 oz

AzaDirect

16.0 oz

AzaDirect

16.0 oz

Carzol

8.0 oz

Carzol

8.0 oz

Carzol

8.0 oz

Carzol

8.0 oz

15

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

16

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

17

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

Warrior

3.84 oz

18

Lannate

3.0 pt

Carzol

12.0 oz

Lannate

3.0 pt

Carzol

12.0 oz

Lannate

3.0 pt

Lannate

3.0 pt

Lannate

3.0 pt

UTC = Untreated check.

^bSeed treated with Regent insecticide.

^cSeed treated with Regent insecticide, straw mulch applied on June 15.

A block of onion 22 ft wide by 648 ft in length was planted to 'Joaquin' (Nunhems, Parma, ID) and a similar-sized block planted to 'Charismatic' (Seminis, Payette, ID) on March 21, 2007. The onions were planted as 2 double rows on a 44-inch bed. The double rows were spaced 2 inches apart. The seeding rate was 137,000 seeds per acre. Lorsban 15G^® was applied at planting in a 6-inch band over each double row at a rate of 3.7 oz/1,000 ft of row for onion maggot control.

The rate and spray interval trial was conducted in the block planted to Joaquin and the insecticide rotation trial was in the block planted to Charismatic. The plots were 27 ft long by 3.67 ft wide. Insecticide applications were made with a CO₂-pressurized backpack sprayer. Materials were applied with water at 41.3 gal/acre. Each treatment was replicated four times. Thrips counts were made weekly by visually counting the total number of thrips on 15 plants in each plot. IYSV severity was evaluated in August. Yield and grade evaluation was completed in late September.

Results

Carzol SP Rate and Spray Interval Trial

Figure 1 shows the average thrips population for each treatment. The weekly application sequence was always significantly better than the 3- or 4-week spray intervals and there was a trend for better control with shorter spray intervals regardless of rate (Fig. 2). There was no significant increase in thrips control with higher rates, although there was a slight trend for better control with the 20-oz rate (Fig. 3). These data suggest that spray frequency is more important than application rate, with 1-week spray intervals being better than longer intervals. Four, 4-oz applications would be more effective than one 20-oz application.

Because of light thrips pressure during the growing season, there were not significant differences in total yield, but there were differences in the supercolossal size class, where the untreated check and some of the 3- and 4-week spray intervals had significantly lower supercolossal yields than the other treatments (Table 2).

Table 2. Onion yield response to different Carzol SP rates and application intervals, Malheur Experiment Station, Oregon State University, Ontario, OR. 2007

Iris yellow spot virus evaluations were made during the first week of August. There was a trend for higher disease ratings with higher thrips populations (Fig. 4), but neither thrips pressure nor disease severity had any effect on total yield.

Carzol SP Rotation Trial

The weekly thrips counts are listed in Table 3, and the season total is shown graphically in Figure 5.

Treatments 1, 4, and 17 had significantly more thrips than the other treatments, with treatment 17 having significantly more thrips than treatments 1 or 4. Treatment 1 is the untreated check, and treatment 4 is an untreated check except for the seed-coat application of Regent^®. Treatment 17 is a synthetic pyrethroid (Warrior^®)-only treatment and illustrates the problem of thrips resistance to this class of insecticides in the Treasure Valley. Synthetic pyrethroid insecticides are not selective and are more harmful to beneficial insect populations than are other insecticides. This treatment had the lowest total yield of any of the treatments (Table 4). As a comparison, treatment 15 is weekly Lannate^® applications, and treatment 16 is a combination of Lannate and Warrior. The addition of the synthetic pyrethroid did not improve thrips control over Lannate alone, and tended to decrease supercolossal and total yield (Fig. 6).

Table 3. Average weekly thrips counts on onions during the 2007 growing season, Malheur Experiment Station, Oregon State University, Ontario, OR. 2007.

Treatment	21-May	1-Jun	7-Jun	12-Jun	18-Jun	22-Jun	26-Jun	2-Jul	10-Jul	16-Jul	23-Jul	1-Aug
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Average thrips/plant - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1	0.3	18.1	39.7	22.8	31.9	15.2	30.9	37.3	10.5	30.8	9.8	27.4
2	0.7	3.1	14.5	14.1	17.8	15.0	23.6	11.4	18.9	16.0	9.2	17.5
3	0.5	3.1	15.2	6.7	14.8	5.0	8.7	7.7	10.1	14.5	10.6	10.2
4	0.5	10.5	25.0	15.4	32.4	14.6	28.3	30.6	16.2	38.0	9.3	28.2
5	0.5	4.8	20.4	10.0	13.9	6.1	13.9	9.6	12.4	13.3	14.5	12.3
6	0.3	7.5	35.7	10.2	13.3	4.6	7.9	9.7	16.7	15.7	11.6	12.5
7	0.5	6.7	21.8	8.8	17.3	4.7	10.6	11.1	8.5	11.2	9.4	10.3
8	0.6	6.0	17.5	9.8	15.7	5.5	11.1	3.6	8.9	11.3	11.6	8.7
9	0.4	6.7	20.3	11.9	15.9	6.2	13.6	7.6	10.8	9.3	12.1	10.3
10	0.9	6.1	22.4	11.6	15.8	5.3	7.3	5.7	10.7	12.0	12.8	8.9
11	0.7	6.2	15.6	12.4	14.1	4.4	9.3	4.4	5.5	13.1	13.5	8.1
12	0.4	7.7	23.8	15.7	28.4	3.2	11.8	5.0	8.2	13.2	12.6	9.5
13	0.6	4.3	17.9	13.2	19.1	4.1	9.4	10.1	12.5	8.4	10.9	10.1
14	0.3	3.3	20.8	12.9	17.5	5.5	5.4	3.6	5.5	10.4	10.2	6.2
15	0.7	1.8	12.0	10.0	14.4	3.8	7.0	8.5	16.4	12.7	17.8	11.1
16	0.6	3.1	12.0	11.3	11.1	4.7	7.4	8.7	16.9	15.6	14.3	12.1
17	0.9	3.5	25.3	15.3	33.1	19.3	34.4	76.9	40.7	58.0	17.7	52.5
18	0.6	2.5	12.9	12.8	16.2	3.4	6.5	7.2	16.0	14.5	10.8	11.1
LSD (0.05)	NS	5.5	9.4	5.3	6.9	3.5	11.6	22.5	12.2	12.8	6.4	NS

Regent was applied to the onion seed coat of treatments 4, 7, 8, and 9, with non-Regent treatments 1, 5, 11, and 13, respectively, as a comparison (Fig. 7). In addition, treatment 9 had straw applied as a mulch on June 15, at a rate of about 1,000 lb/acre. The Regent treatments had higher yields than the nontreated in 3 of the 4 treatments, but it was only significant in treatment 8 versus treatment 11, which was the grower standard treatment. The Regent treatments were made with seed treated in the spring of 2006, and may have lost some of its effectiveness during storage. The Regent plus straw mulch was not better than the comparison treatment (treatment 13).

Treatment 2 had 4 8-oz treatments of Carzol SP applied at 2-week intervals. It had significantly higher average thrips numbers compared to the best treatments, but provided high total yield in spite of the high thrips counts (Table 4). These data suggest that 3 8-oz applications (legal application rate of Carzol SP is 24 oz/acre under 2006 and 2007 Section 18 emergency registrations) might be better than the single 20-oz application that growers are currently using. They should be integrated into the grower standard practice of using spinosad insecticides (Success, Radiant) early, followed by Carzol SP, then finish the season with Lannate.

There was no relationship between average thrips population and IYSV disease incidence (Fig. 8), or between thrips population and total yield (Fig. 9). However, there was a good correlation between disease incidence and total yield (Fig. 10).

Table 4. Carzol SP rotation trial on onion yield, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Treatment	Medium	Jumbo	Colossal	Super-colossal	Colossal + Supercol.	Total yield
	- - - - - - - - - - - - - - - - - - - - - - - - -cwt/acre - - - - - - - - - - - - - - - - - - - - - - - - -
1	9.7	291.5	612.5	295.7	908.2	1209.4
2	12.3	305.3	629.2	357.4	986.6	1304.3
3	14.3	359.9	553.8	192.3	746.1	1120.3
4	28.0	680.8	481.5	76.7	558.2	1267.0
5	13.9	341.0	523.9	205.3	729.2	1084.1
6	5.9	351.8	521.4	152.6	674.0	1031.7
7	26.3	555.2	503.0	62.7	565.7	1147.3
8	32.3	609.9	543.7	142.3	686.1	1328.3
9	29.3	512.3	478.4	162.7	641.1	1182.8
10	6.0	374.6	554.8	261.6	816.4	1197.0
11	10.7	311.9	516.2	309.4	825.6	1148.2
12	13.0	394.7	558.3	221.2	779.4	1187.1
13	14.1	349.3	555.9	299.4	855.3	1218.8
14	19.1	367.5	492.2	380.1	872.3	1259.0
15	8.9	320.5	565.5	281.9	847.4	1176.9
16	13.8	375.9	587.1	154.2	741.3	1131.0
17	20.1	588.7	374.0	48.3	422.3	1031.2
18	5.0	337.7	500.5	293.3	793.8	1136.5
LSD (0.05)	12.7	119.4	N.S.	103.6	180.3	152.4

Conclusion

Carzol SP Rate and Spray Interval Trial

The results from 2007 were similar to those from 2006, and show that shorter spray intervals (7-14 days) are more important to both thrips control and yield than longer spray intervals. Rate was also important, but not as important as application interval.

Carzol SP Rotation Trial

Synthetic pyrethroid effect varied, depending on treatment, from no effect, to significantly less thrips control and lower yields. Growers are urged not to add this class of insecticides to their tank mixes unless they know they have had positive experiences with them on their farm.

Regent did not perform as well in 2007 as in 2006. This may be due to the use of seed treated for the 2006 crop. There was still a positive effect on yield in most of the treatments.

Multiple applications of Carzol SP at the 8-oz rate appear better than a single 20-oz application.

With Joaquin, there was no relationship between total yield and either thrips or IYSV, but there was with Charismatic, indicating that Joaquin may have more resistance to thrips, IYSV, or both.

Figure 1. Carzol SP rate and spray interval trial in onions. Average season-long thrips populations at different Carzol rates and spray intervals, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Figure 2. Carzol SP rate and spray interval trial in onions. Average season-long thrips populations with different spray intervals using the insecticide Carzol, averaged over the 8-, 12-, 16- and 20-oz rates, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.\

Figure 3. Carzol SP rate and spray interval trial in onions. Average season-long thrips populations at different Carzol application rates, averaging 1-, 2-, 3- and 4-week timing sequences, Malheur Experiment Station, Oregon State Univeristy, Ontario, OR, 2007.

Figure 4. Carzol SP rate and spray interval trial in onions. Average seasonal thrips population relationship to iris yellow spot virus evaluation (0 = no damage, 5 = dead plant), Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Figure 5. Carzol SP rotation trial in onions; seasonal thrips populations during the 2007 growing season, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.

Figure 6. Carzol SP rotation trial: pyrethroid impact on onion yield, Malheur Experiment Station, Oregon State University, Ontario, OR, 2007.