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2018 IPM Survey Results – Soybean and Sunflower Insect Pests (09/13/18)

The purpose of the IPM (Integrated Pest Management) Survey is to detect the presence and population levels of diseases and insect pests that are common in soybeans and sunflowers grown in North Dakota.

2018 IPM Survey Results – Soybean and Sunflower Insect Pests

The purpose of the IPM (Integrated Pest Management) Survey is to detect the presence and population levels of diseases and insect pests that are common in soybeans and sunflowers grown in North Dakota. Ten survey scouts or insect trappers operated out of the Dickinson Research Extension Center, the North Central Research Extension Center (Minot), the Carrington Research Extension Center, the Langdon Research Extension Center, the Williston Research Extension Center and the Fargo Agricultural Experiment Station. The NDSU IPM scouts were:

  • Brittney Aasand, central and south central counties, worked out of Carrington REC with Greg Endres
  • Marc Michaelson, southwest and west central counties, worked out of Dickinson REC with Ryan Buetow
  • Caleb Cross and Bree Obergfell, north central counties, worked out of NCREC in Minot with Travis Prochaska
  • Scott Roseth and Jace Paryzek, northwest counties, worked out of Williston REC with Audrey Kalil
  • Dan Kraemer and Stafford Thompson, southeast and east central counties, worked out of NDSU campus, Fargo with Jan Knodel, Andrew Friskop and Sam Markell.
  • Kaylee Anderson and Traci Murphy, northeast counties, worked out of Langdon REC with Leslie Lubenow and Benson County Extension Office with Scott Knoke

NDSU IPM field scouts surveyed a total of 544 soybean fields and 101 sunflower fields in North Dakota during 2018. The survey was initiated in early June and continued through August 10. Crops were surveyed from the 2-leaf stage through R5 growth stage in soybeans and R6 growth stage in sunflowers. IPM survey data/maps provide near real-time pest information to North Dakota producers and others in agriculture to assist with scouting and pest management decision making. Pest maps from the 2018 IPM Survey in North Dakota were uploaded weekly onto the NDSU IPM website. Some of the insect pest highlights for soybean and sunflower are summarized below.

Soybean Insect Pests:

Soybean aphids - No soybean aphids were observed in 82% of the soybean fields surveyed. The percent of plants infested with soybean aphids in fields was low with an average of 17% of plants infested and ranged from 1 to 100% of plants infested. The higher percentage of plants infested with soybean aphids in fields were found late in the season (August) and mainly in Cass and Richland Counties. The average number of aphids per plant was only 3 aphids per plants and ranged from 1 to 59 aphids per plant. Soybean aphids never reach 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 scouted in 2018. This just goes to show why it is good to scout and use E.T. for soybean aphids!

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Spider mites were observed in only 4% of the field scouted. Hot spots for spider mites were common on the field edges and in the droughty areas of ND, especially in the northwest including Divide, Williams, Mountrail and Burke Counties.

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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 our cold winters. However, the IPM scouts collected low numbers of bean leaf beetles in sweep net samples in three counties:  Stutsman, Sargent and Richland.

During the last two weeks of the soybean survey, scouts looked for dicamba herbicide injury on soybeans. Dicamba injury was observed in about 14% of the 118 soybean fields surveyed in late summer.

 

Sunflower Insect Pests:

Red sunflower seed weevils were found in 72% of the sunflower fields that were scouted during flowering. The average number of weevils per head was 3.7 and ranged from 1 to 18 weevils per head depending on field site. Counts that were taken on field edges were higher and averaged 6 weevils per heads compared to 2.8 weevils per heads in field (at least 25 feet into field). In 2018, the E.T. for red sunflower seed weevils was 4-6 weevils per head for oilseed sunflowers. Approximately 36% of the fields with weevils present were above the E.T. and these fields needed to be treated with insecticides. The hot spots included Stark, Mercer and Emmons Counties.

 

Banded sunflower moth was collected at all 10 trap sites throughout ND. The first moth was trapped on June 21st and peak moth catch was the last week of July. Moth capture varied depending on field site but overall an average of 344 total moths were captured per field site. Counties with more than 100 moths per trap per week included:  Cass, Foster, Divide, Mountrail, Renville, Ward and Towner.

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Sunflower moth was collected at 7 of the 10 trap sites. The sunflower moth migrates annually into ND and was first detected on June 28th. The peak catch occurred during late July into early August. None of the trap sites reached the trap economic threshold for sunflower moths (> 25 moths per trap per week). The average trap catch among sites was only about 5 moths per trap per week.

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Acknowledgments:  Sincere thanks to the hard working field scouts of 2018! 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.

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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