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2020 Soybean and Sunflower IPM Survey (09/24/20)

NDSU IPM field scouts surveyed a total of 563 soybean fields and 181 sunflower fields in North Dakota during 2020.

NDSU IPM field scouts surveyed a total of 563 soybean fields and 181 sunflower fields in North Dakota during 2020. The survey was initiated in early June and continued through August 15. Crops were surveyed from the 2-leaf stage through R5 growth stage in soybeans and R6 growth stage in sunflowers. Some of the insect pest highlights for soybean and sunflower are summarized below.

Soybean Insect Pests:

Soybean aphids - No soybean aphids were observed in 96% of the soybean fields surveyed. The percent of plants infested with soybean aphids in fields was very low with an average of 14% of plants infested and ranged from 2 to 58% of plants infested. The average number of aphids per plant was only 2 aphids per plant and ranged from 1 to 11 aphids per plant. Most of the positive fields were located in southeast (Cass, Dickey, Ransom, Richland, Sargent, Traill Counties). Soybean aphids never reached the economic threshold (E.T.) level (average of 250 aphids per plant, 80% of plants infested with one or more aphids and increasing population levels) in any of the fields.

ent.10.soybean aphids

Soybean - Spider mites were observed in only 2% of the fields scouted. Mites were found on the field edges and were non-economic.

Sunflower Insect Pests:

Red sunflower seed weevils were observed during flowering from late July through mid-August. The average number of weevils per head was 2.3 and ranged from 1 to 11 weevils per head depending on field site. In 2020, the E.T. for red sunflower seed weevils was 4-6 weevils per head for oilseed sunflowers. Approximately 3% of the fields surveyed were above the E.T. and these fields required an insecticide application.

ent.12 13.soybean spider mites.red sunflower seed weevils

Banded sunflower moth was collected at all 12 trap sites throughout ND. The first moth was trapped on July 2nd and peak moth catch was the late July through mid-August during flowering. Traps that captured more than 100 moths per trap per week were located in Cass, Foster, Renville and Ward Counties.

Sunflower moth was collected at 9 of the 10 trap sites, not trapped in Cavalier County. The sunflower moth migrates annually into ND and was first detected during late June. Peak catch occurred during mid- to late July during flowering. Economic numbers of sunflower moths (> 25 moths per trap per week) were observed at western trap sites in southwest (Dunn, Golden Valley Counties) and north central (Renville County).

ent.14 15.banded sunflower moth trapping network

Sunflower Diseases: The IPM scouts scouted for downy mildew and rust. A low level of downy mildew was observed with the disease being detected in less than 7% of the fields. The percentage of plants infected with downy mildew ranged from 4-22%. Sunflower rust was not observed, since most scouting was completed prior to growth stages R5-R6, when sunflower rust is most commonly observed in the state.

ent.16.sunflower downy mildew percent

ent.final acknowledgments

 

Janet J. Knodel                                                                                                  Andrew Friskop

Extension Entomologist                                                                                 Extension Plant Pathology, Cereal Crops

 

Patrick Beauzay                                                                                                Sam Markell

State IPM Coordinator and Research Specialist                                    Extension Plant Pathologist, Broad-leaf Crops

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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