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June 9, 2010

Small Grains:

-We started seeing aphids (English grain aphids) in small grains last week. 

-Grasshopper populations are low.

-Tan spot (wheat) and net blotch (barley) fungal diseases are widespread in most fields.

-In addition to winter and spring wheat, we have confirmed cases of wheat streak mosaic virus in barley, rye, and spelt. 

-Barley thrips: Early this week I was in a barley field in southwest Bottineau County with a healthy population of barley thrips.  Female barley thrips overwinter in sod, especially in shelter belts with a preference for brome and Kentucky blue grass.  Thrips are weak fliers but can move short distances in a field by flying.  They can also be spread by wind.   To determine the need for an insecticide application, the top two sheaths of a barley plant should be examined in at least nine separate areas of a field prior to heading.  After heading it is not economical to spray for this particular pest.  Barley thrips can be concentrated along field edges so it is important to sample from interior field locations as well as edges.  A sampling plan from work done in North Dakota and Alberta is listed below.   Only methyl parathion is registered for control of barley thrips in barley.  However, pyrethroid insecticides (e.g., Baythroid, Grizzly, and Warrior) used to control other barley insects should give good control of barley thrips (Jan Knodel, NDSU Entomology).     

Decision Table for Barley Thrips Sequential Sampling Plan

 

# Samples

Don't Treat

Treat

9

33

88

18

83

160

27

135

229

36

188

298

45

243

365

54

298

431

63

353

497

 

Sources: http://www.ag.ndsu.edu/procrop/bar/bythrp06.htm http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm2477?opendocument

 

Canola: We have seen some flea beetle feeding in canola fields in the area but none above the 25% damage threshold that warrants an insecticide application. Striped flea beetles have been caught in our traps in McHenry, Ward, and Towner counties.  The crucifer flea beetle has been the exclusive canola flea beetle species caught in traps in McKenzie, Renville, Bottineau, McLean, and Burleigh counties.  In the areas where we’ve caught striped flea beetles, they comprise less than 10% of the total flea beetles caught.  At this point, we have not observed the dramatic population shift from crucifer to the more insecticide tolerant striped flea beetles that areas of Canada have experienced. 

 

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