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A Field Scouting Strategy for Red Sunflower Seed Weevil

New research at NDSU suggests that to increase the accuracy of sampling for the red sunflower seed weevil under field conditions, producers should spray the head with a commercial formulation of mosquito repellent and correct for sampling efficiency. Corrected estimates are provided in Table 1.

It is recommended that sunflower producers who are producing oilseed sunflower use the following steps for red sunflower seed weevil management.

Step 1. Calculate the number of red sunflower seed weevil needed before an insecticide should be applied using the formula below.

    weevils/head =                                Cost of Insecticide
                                    (Market price X 21.5) (0.000022 X plant population/0.18)

Step 2. Sample each field in a Z-pattern beginning at least 75 feet from the field margin. At each of five locations in the field, sample five sunflower heads, spraying each head with a commercial formulation of mosquito repellent before counting. The total number of sunflower heads that should be sampled for each field should be at least 25.

Step 3. Correct each count (number of red sunflower seed weevil per head) for sampling efficiency using the corrected estimate in Table 1.

Step 4. If the corrected estimated average (total corrected estimates/25) is equal to or exceeds the insecticide treatment threshold from Step 1, an insecticide application should be considered.

Table 1. Estimation of total red sunflower seed weevil adults when sampling using a commercial formulation of mosquito repellent
Number counted in the field Estimated Number Number counted in the field Estimated Number
1 1.44 16 29.25
2 2.90 17 31.08
3 4.35 18 32.91
4 5.80 19 34.73
5 7.25 20 36.56
6 10.66 21 38.46
7 12.43 22 40.29
8 14.21 23 42.12
9 15.99 24 43.96
10 17.76 25 45.79
11 19.54 26 45.29
12 21.31 27 47.04
13 23.09 28 48.78
14 24.87 29 50.52
15 26.64 30 52.26

THRESHOLD FOR CONFECTION SUNFLOWER

Red sunflower seed weevil control on confection sunflower is based on a need to keep seed damage below 3 or 4 percent due to industry standards. Treatment is recommended when 1 to 2 weevils are found per plant.

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