North Central Research Extension Center


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May 26, 2010

Late last week I was in some late April planted canola in Burleigh County.  Flea beetles and resulting damage were found on two-leaf seedlings especially on field edges.  These fields did have an insecticide treatment, however, the insecticide was no longer effective.  Twenty-one days after planting, insecticide treatments for flea beetles begin to lose their efficacy.  Twenty-five days after planting, even the high rates of insecticide seed treatments do not effectively control flea beetles on canola (Jan Knodel, NDSU Entomology).  Any canola planted in the first week of May or earlier should be scouted to determine if insecticides need to be applied.  Insecticides are generally not economical until flea beetles cause 25% defoliation (see example at ).  Once the 25% threshold is reached it is important to treat fields within 24 hours because damage can progress rapidly. 

  A winter wheat sample from Ward County tested positive for barley yellow dwarf virus.  This infection probably started last fall when aphid activity was high.  This virus is spread by aphids unlike the mite-vectored wheat streak mosaic and high plains viruses.  Aphids can acquire the virus after 24-48 hours of feeding and keep the virus for life.  Symptoms include yellowing and then red to purple discoloration.  Barley yellow dwarf virus infects more than 80 species of annual and perennial grasses including corn and small grains.  Yield reduction from this virus is significant on wheat, barley, and oats.  The disease can be managed by planting spring cereals early, winter wheat late, and using resistant cultivars.  Foliar applications of insecticides can be used to control aphids.  Insecticide seed treatments may be useful on winter wheat that emerges during high aphid activity. 


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