Directions for using the Quick Count:
1. Walk at least 15-20 feet into the sorghum field to begin sampling in one row.
2. Grasp the stalk just below the emerged sorghum head, bend the head into the bucket opening and vigorously beat the head against the side of the bucket. Headworms will fall into the bucket where they can be seen and counted.
3. Walk 30 paces down the row and sample another head, then walk 30 more paces and sample another head in the same row.
4. After sampling 3 plants, stop, count and record the total number of medium size (¼-½ inches long) and large (greater than ½ inches long) headworm caterpillars in the bucket. Ignore all caterpillars less than ¼ inches long. Refer to the Quick Count sampling form examples and links below to determine thresholds based on your sampling. If there are mostly large caterpillars, use the Large Threshold. If there are mostly Medium-sized caterpillars, use the Medium Threshold. If there are about 50% large and medium, use the Mixed Threshold.
5. Sample 3 more plants in the same row and add the counts from the previous 3 plants, and add the caterpillar totals.
6. After sampling 6 plants within a row, move over 25 rows and continue the process for each 6 heads.
7. Now, complete the process using the Headworm Calculator to determine your threshold (http://entoweb.okstate.edu/shwweb/welcome%20page.htm). Based on your thresholds, use the appropriate Quick Count Form (http://entoweb.okstate.edu/shwweb/Sequential_Sampling.htm).
8. For each form, compare counts with numbers in red (right) and green (left) boxes. If they equal or exceed the “Treat” box, then stop and treat. If they equal or are lower than the “Don’t Treat Box, then stop sampling and Don’t Treat. If they fall in the yellow “sample” box, keep sampling until you have sampled 48 heads. If you still can’t make a decision at Stop #16, return in 3 days and resample the field.
Based on the threshold determined by the Headworm Calculator, use the following forms for accurate sampling:
More at: entoplp.okstate.edu/shwweb/index.htm for more forms and information!
Example form format:
|
|
|
|
|
|
Large |
Medium |
Small |
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|
Stop# |
3 more heads |
|
Previous Total |
New Total |
Do Not Treat |
Sample 3 More Heads |
Treat Field |
Do Not Treat |
Sample 3 More Heads |
Treat Field |
Do Not Treat |
Sample 3 More Heads |
Treat Field |
|
1 |
First 3 heads |
= |
___ |
0 to 1 |
2 or more |
1 or less |
2 to 4 |
4 or more |
--- |
0 to 2 |
3 or more |
||
|
2 |
|
+ |
|
= |
___ |
0 to 1 |
2 or more |
2 or more |
5 to 7 |
8 or more |
1 or less |
2 to 4 |
5 or more |
|
3
|
|
+ |
|
= |
0 |
1 to 2 |
3 or more |
3 or more |
8 to 10 |
11 or more |
3 or less |
4 to 5 |
6 or more |
|
4 |
|
+ |
|
= |
1 or less |
2 to 3 |
4 or more |
4 or more |
12 to 14 |
15 or more |
5 or less |
6 to 7 |
8 or more |
|
5 |
|
+ |
|
= |
2 or less |
3 |
4 or more |
4 or more |
15 to 17 |
18 or more |
6 or less |
7 to 9 |
10 or more |
|
6 |
|
+ |
|
= |
2 or less |
3 to 4 |
5 or more |
5 or more |
18 to 20 |
21 or more |
8 or less |
9 to 10 |
11 or more |
|
7 |
|
+ |
|
= |
3 or less |
4 to 5 |
6 or more |
6 or more |
21 to 23 |
24 or more |
10 or less |
11 to 12 |
13 or more |
|
8 |
|
+ |
|
= |
3 or less |
4 to 5 |
6 or more |
6 or more |
25 to 27 |
28 or more |
11 or less |
12 to 13 |
14 or more |
|
9 |
|
+ |
|
= |
4 or less |
5 to 6 |
7 or more |
7 or more |
28 to 30 |
31 or more |
13 or less |
14 to 15 |
16 or more |
|
10 |
|
+ |
|
= |
5 or less |
6 to 7 |
8 or more |
8 or more |
31 to 33 |
34 or more |
15 or less |
16 to 17 |
18 or more |
|
11 |
|
+ |
|
= |
5 or less |
6 to 7 |
8 or more |
8 or more |
34 to 36 |
37 or more |
16 or less |
17 to 19 |
20 or more |
|
12 |
|
+ |
|
= |
6 or less |
7 to 8 |
9 or more |
9 or more |
38 to 40 |
41 or more |
18 or less |
19 to 20 |
21 or more |
|
13 |
|
+ |
|
= |
7 or less |
8 to 9 |
10 or more |
10 or more |
41 to 43 |
44 or more |
20 or less |
21 to 22 |
23 or more |
|
14 |
|
+ |
|
= |
7 or less |
8 to 9 |
10 or more |
10 or more |
44 to 46 |
47 or more |
21 or less |
22 to 24 |
25 or more |
|
15 |
|
+ |
|
= |
8 or less |
9 to 10 |
11 or more |
11 or more |
47 to 49 |
50 or more |
23 or less |
24 to 25 |
26 or more |
|
16 |
|
+ |
|
= |
9 or less |
10 |
11 or more |
11 or more |
51 to 53 |
54 or more |
25 or less |
26 to 27 |
28 or more |
|
If you still can’t make a decision at stop #16, then return in 3 days and resample the field. Use caterpillar size from first 3 heads to choose threshold here: |
Economic threshold for Large Headworms: 0.25/head |
Economic threshold for Medium Headworms: 1.3/head |
Economic threshold for Small Headworms: 0.80/head |
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This content may not be suitable for use outside of Kansas.
|
Corn Earworm Management Options |
|
|
Insecticide |
Rate |
|
Alpha-cypermethrin (Fastac EC) |
1.8 to 3.8 fl. oz./acre |
|
Beta-cyfluthrin (Baythroid XL) |
0.010 to 0.022 lbs. a.i./acre (1.3 to 2.8 fl. oz.) |
|
Chlorantraniliprole (Prevathon) |
14.0 to 20.0 fl. oz./acre |
|
Chlorpyrifos (numerous products) |
Check label, but generally 2 pints/acre. |
|
Chlorpyrifos plus gamma-cyhalothrin (Cobalt Advanced) |
19 to 38 fl. oz. of product/acre |
|
Chlorpyrifos plus zeta-cypermethrin (Stallion) |
5.0 to 11.75 fl. oz./acre |
|
Deltamethrin (Delta Gold) |
0.012 to 0.018 lb. a.i./acre (1 to 1.5 fl. oz.) |
|
Esfenvalerate (Asana XL 0.66) |
0.03 to 0.05 lb. a.i./acre (5.8 to 9.6 fl. oz.) |
|
Gamma-cyhalothrin (Proaxis) |
0.01 to 0.015 lb. a.i./acre (2.56 to 3.84 fl. oz.) |
|
Lambda-cyhalothrin (numerous products) |
0.02 to 0.03 lb. of a.i./acre |
|
Methomyl (Lannate) |
0.225 to 0.45 lb a.i./acre |
|
Spinosad (Blackhawk) |
0.038-0.075 lb. a.i./acre (1.7 to 3.3 fl. oz.) |
|
Zeta-cypermethrin (Mustang MAXX, Respect EC) |
0.011 to 0.025 lb. a.i./acre (1.76 to 4.0 fl. oz.) |
|
Fall Armyworm Management Options |
|
|
Insecticide |
Rate |
|
Alpha-cypermethrin (Fastac EC) |
1.8 to 3.8 fl. oz./acre |
|
Beta-cyfluthrin (Baythroid XL) |
0.010 to 0.022 lbs. a.i./acre (1.3 to 2.8 fl. oz.) |
|
Chlorantraniliprole (Prevathon) |
14.0 to 20.0 fl. oz./acre |
|
Chlorpyrifos (numerous products) |
Check label, but generally 1 to 2 pints/acre. |
|
Chlorpyrifos plus gamma-cyhalothrin (Cobalt Advanced) |
11 to 38 fl. oz. of product/acre |
|
Chlorpyrifos plus zeta-cypermethrin (Stallion) |
9.25 to 11.75 fl. oz./acre |
|
Deltamethrin (Delta Gold) |
0.015 to 0.022 lb. a.i./acre (1.3 to 1.9 fl. oz.) |
|
Gamma-cyhalothrin (Proaxis) |
0.01 to 0.015 lb. a.i./acre (2.56 to 3.84 fl. oz.) |
|
Lambda-cyhalothrin (numerous products) |
0.02 to 0.03 lb. of a.i./acre |
|
Methomyl (Lannate) |
0.225 to 0.45 lb a.i./acre |
|
Spinosad (Blackhawk) |
0.038-0.075 lb. a.i./acre (1.7 to 3.3 fl. oz.) |
|
Zeta-cypermethrin (Mustang MAXX, Respect EC) |
0.011 to 0.025 lb. a.i./acre (1.76 to 4.0 fl. oz.) |