Oklahoma State University

Sorghum Headworm Sequential Sampling System

Tom A. Royer

Department of

Entomology&

Plant Pathology

Oklahoma State University

Development of Headworm Sampling System

Data on Economic and Treatment thresholds collected from Texas, Oklahoma, and Kansas (Elliott et al. 2012)

Objectives: Create a simple, dynamic, economically accurate

sampling strategy for sorghum headworms Develop an educational tool with information on

headworm identification, and other sorghum pests. Develop a flexible system that could be expanded as

additional information became available and/or interface with real-time platform (such as I-Wheat).

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The Product

A computer program located at http://entoplp.okstate.edu/shwweb/index.htm

It has several elements:1. Information on sorghum headworm2. A calculator for determining economic thresholds for headworm

infestations3. Sequential sampling forms4. Sampling instructions5. Information on other sorghum pests

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It allows a producer to play the “what If” game with pesticide costs, market values

What Does the Headworm Decision Support System Provide?

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It has a full complement of treatment threshold forms that can be printed off to serve as a permanent record of the sampling results

What Does the Headworm Decision Support System Provide?

Assumptions: The Scout Needs to: Estimate sorghum plant populations Estimate composition of headworm sizes

(Large, Medium, Mixed) Mostly large headworms > ½ inch cause significant

damage Mostly medium headworms ¼ to ½ inches will also

cause damage (less so, due to field mortality) Small headworms < ¼ inches are not counted

because many will die

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What You Need to Know Plant Density

Number of sorghum heads per acre Number of sorghum heads per length of row spacing Pounds of seed planted per acre

(assume that a pound of seed per acre results in 35,000 heads per acre

None of the Above (assume that 1 inch of rainfall results in 1100 heads per

acre. Inches of rainfall is determined by clicking your location on the map.

(3 or 4 won’t give you as accurate an estimate)

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What You Need to Know Value of crop ($ per hundredweight)

Control Cost ($ per acre)

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What You Need to Know

Directions1. Walk 15-20 feet into field2. Grasp and bend head into bucket and

shake vigorously3. Walk 30 paces in row to next sample,

repeat 24. Walk 30 paces to next sample, repeat

2 (STOP 1)5. Count medium (1/4 – ½ inches) and

large > ½ inches) caterpillars, and determine whether most are Medium, Large or a Mixture (ca. 50/50).

Sampling Technique

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What You Need to Know

Directions1. Sample 3 more heads, combine

count from first three heads with new count, mark total in box (STOP 2). Determine if you need to treat, not treat, or sample 3 more heads.

2. If you need to sample 3 more heads, move over 25 rows, and sample 3 heads.

3. Repeat 1 (STOP 3).4. Repeat 1, and move over 25 rows

AFTER you sample 6 heads in each row.

Sampling Form

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What You Need to Know

Directions1. If you sample at 16 stops and

still can’t make a decision, return in 3 days and resample the field.

Sampling Form

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Data on time to decision.10 fields, 16 stops, no decision made:

10 fields, no treatment after 3 stops, 9 samples

Average time per stop:

Average time: 19 minutes 37 seconds

Average time: 3 minutes 4 seconds

1 minute 12 seconds

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Next?.

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An Application for Smart Phone use in field.

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Thanks!