Alert Update: Sugarbeet Root Maggot

Published online: May 25, 2010 PNWPestAlert.net
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A new sugarbeets alert was posted Alert Information: The degree day calculator (hosted by the Integrated Plant Protection Center at Oregon State University) for the sugarbeet root maggot fly shows that-depending on your location in the Magic Valley-we have accumulated about 237 degree days since March 1, 2010. Peak emergence of root maggot flies should occur around 350 accumulated degree days when the maximum high temperature exceeds 80 degrees F. In the Mini-Cassia area, this usually occurs around the 2nd of June. With recent temperatures being cooler than average, peak flight should occur slightly later (around the 5th of June in the Rupert area). Monitoring flies adjacent to your sugar beet fields using orange sticky stake traps will provide even more useful information regarding the local population densities of flies. The Amalgamated Sugar Company monitors flies with sticky stake traps throughout the Mini-Cassia area and posts the counts on their website: http://www.srcoop.com/ The economic threshold for application of granular insecticides against root maggots is an accumulative total of 40-50 sugarbeet root maggot flies per sticky stake trap (the threshold varies depending on your contract price per ton). In the Mini-Cassia area, which historically has had high root maggot pressure, growers should consider an insecticide application 10 days before exceeding threshold captures on sticky stakes. Otherwise, insecticide applications should be made within 10 days before or after reaching the threshold (the closer to the threshold date, the better). Activation of granular insecticides should be accomplished by irrigation as soon after application as possible. See University of Idaho publication CIS 999, IPM Guide to Sugar Beet Root Maggot: http://www.uiweb.uidaho.edu/sugarbeet/insc/sbmaggot.htm