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2019 ND IPM Survey Results in Soybean and Sunflower (09/12/19)

NDSU IPM field scouts surveyed a total of 489 soybean fields and 144 sunflower fields in North Dakota during 2019.

NDSU IPM field scouts surveyed a total of 489 soybean fields and 144 sunflower fields in North Dakota during 2019. The survey was initiated in early June and continued through August 16. 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 93% of the soybean fields surveyed. The percent of plants infested with soybean aphids in fields was very low with an average of 28% of plants infested and ranged from 3 to 100% of plants infested. The average number of aphids per plant was only 6 aphids per plants and ranged from 1 to 10 aphids per plant. 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.

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Spider mites were observed in only 1% of the field scouted. Mites were found on the field edges and in the droughty areas of ND, especially in the northern half of North Dakota. 

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Bean leaf beetle is an uncommon insect pest of soybeans in ND. It usually does not overwinter successfully in ND due to our cold winters. No bean leaf beetles were observed in soybean fields scouted in 2019.

 

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 3.3 and ranged from 1 to 12 weevils per head depending on field site. Counts that were taken on field edges were higher and averaged 2 weevils per heads compared to 0.5 weevils per heads in field (at least 25 feet into field). In 2019, the E.T. for red sunflower seed weevils was 4-6 weevils per head for oilseed sunflowers. Approximately 15% of the fields were above the E.T. and these fields needed to be treated with insecticides.

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Banded sunflower moth was collected at all 12 trap sites throughout ND. The first moth was trapped on July 9th and peak moth catch was late July through mid-August. Traps that captured more than 100 moths per trap per week were located in Burke, Cass, Cavalier and Renville Counties.

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Sunflower moth was collected at 10 of the 12 trap sites. The sunflower moth migrates annually into ND and was first detected late on July 12th. The peak catch occurred during late July into early August. Economic numbers of sunflower moths (> 25 moths per trap per week) were not observed at any trap site in North Dakota. However, traps sites located in Foster, McIntosh and Burke had the highest moth trap catches of 21 moths per trap per week.

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Sunflower Diseases: The IPM scouts scouted for downy mildew and rust in 144 fields this year. A low level of downy mildew was observed with the disease being detected in less than 4% of the fields (Figure 1). Sunflower rust prevalence this year was also low (<3% of the fields). However, most scouting efforts were completed prior to growth stages R5-R6 when sunflower rust is most commonly observed in the state.

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Acknowledgments:  Sincere thanks to the hard working field scouts of 2019! We also appreciate the help of Darla Bakko, NDSU Dept. of Plant Pathology, for data compilation, and Honggang Bu, NDSU Dept. of Soil Science, for ArcMap programming. This survey is supported by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture.

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Janet J. Knodel                                                                                                  Andrew Friskop

Extension Entomologist                                                                                 Extension Plant Pathology, Cereal 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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