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Spray Timing Important for Effective Sunflower Insect Control (08/01/19)

Once sunflower insects reach their established economic thresholds and the decision to treat has been made, it is critical to time the spray application correctly to get effective management of all sunflower head insects including red sunflower seed weevils, banded /Arthuri sunflower moths, sunflower moths and Lygus bugs (for confection sunflowers only).

Once sunflower insects reach their established economic thresholds and the decision to treat has been made, it is critical to time the spray application correctly to get effective management of all sunflower head insects including red sunflower seed weevils, banded /Arthuri sunflower moths, sunflower moths and Lygus bugs (for confection sunflowers only).

The best sunflower plant stage to treat for all of these head-infesting insect pests is when the majority of the plants are in the early flowering R5.1 growth stage (when pollen shed on 10% of the outer rim of the sunflower head).

Scheduling an airplane may take a week or more if ag pilots are busy spraying, so we recommend planning for your insecticide application when only 30% of the plants in a field reached the R5.1 growth stage. If it’s hot, flowering will progress more rapidly and one week may not be enough lead time. Getting the timing right in this situation is difficult, but making arrangements when 5-10% of plants are at R5.1 may be more prudent. At Casselton in 2017, sunflower progressed from 1% at R5.1 to 50% at R5.1 in just a few days. Insecticides should be targeted at the adult RSSWs to prevent egg laying; at the adult and early larval stages of BSM and sunflower moth; and at the adult or nymph stages of Lygus bug.

Please see the NDSU Extension E1143 2019 ND Field Crop Insect Management Guide for insecticides registered in sunflower. Please remember that blooming sunflowers are attractive to bees, so insecticides should be applied in the late evening (preferred by honeybee keepers) or early morning to minimize negative effects of an insecticide on bees. See the ND Department of Agriculture bee map for help finding the locations and owners of hives.

Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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