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AG DEVELOPMENT DIVISION <br /> MINNESOTA MI\INESOTA DEPARTMENT OF AGRICULTURE <br /> P+E+S+T E+P+O+R+T <br /> MPR 14-00 Gene Hueoson.Commissioner Autust 25. 2000 <br /> Sovbeans <br /> After last weeks report of Aphis glycines(soybean aphid)in Wisconsin.we began a special survey to determine if the <br /> aphid was present in Minnesota—and if so,to map its distribution. Since August 18,we have found aphids resembling <br /> A.glycines in 6 Minnesota Counties: <br /> Houston,Winona,Wabasha,Goodhue, <br /> Fillmore and Olmsted. However,while �.. <br /> these aphids resemble.4.glvcines they_ t° <br /> have not been yet been confirmed as i";- FJ _ <br /> such. The greatest aphid abundance is 3 k <br /> in Houston and Winona Counties --? j <br /> where every field checked has <br /> contained aphids. Wabasha Countyr °fi of sayban Qiarrts with aphids '' <br /> has also had aphids found in every 0 ,,x <br /> field,however only 2 fields have been �-,,-�-3" <2 <br /> visited. Goodhue,Fillmore and • »- } . 5D <br /> Olmsted Counties have produced fields50-75 <br /> with and without aphids. In addition <br /> to these counties.University of <br /> Minnesota researchers have found "--` <br /> aphids resembling A.glycines in f —=-- <br /> • Ramsey and Dakota Counties. Finally, y• •- +just <br /> --- <br /> just today a specimen came in from <br /> Meeker Counry that resembles the :• �';- <br /> soybean aphid. All other counties J.----It <br /> � •+•+ <br /> remain negative for aphids of any kind <br /> 1 . .;�+ • - <br /> in soybeans(see map). Fields are '. <br /> car ••:i' <br /> checked for aphids by inspecting 10 <br /> whole plants,each separated by at least - <br /> 10 m. The infestation is quantified by + <br /> expressing the number of plants ., •+ • "`�--r <br /> infested per 10 checked as a percentage F <br /> for the field. 1n addition.the <br /> abundance of aphids on each plant isrr= �._L_'. z+ •�P <br /> rated aS <br /> • Light=aphids present but rare <br /> • Moderate=aphids easily found but not abundant <br /> • Heavy=plant inundated with aphids <br /> ; Aphid abundance on all infested plants has been rated as light. In fact,we are regularly finding only 1-2 aphids on 1 <br /> leaf per plant. This low abundance may be partially due to the time of year as soybeans are reaching maturity and <br /> —� soybean aphids would be switching to their primary host.European buckthorn—an exotic forest weed./Observations <br /> made by University of Minnesota Entomologist Ken Ostlie of an aphid infested field in Wisconsin indicate that the <br /> damage caused to plants may be distinctive. Leaf discoloration is found that resembles a potassium deficiency where <br /> the leaf surface along the veins remains green but the rest of the leaf turns yeilow. We sported these symptoms in <br /> relatively few fields during our survey. Some fields where these symptoms were found contained aphids,others did <br /> not. This may indicate that aphid populations were more abundant earlier in the season. The picture below was taken <br /> in a field in Goodhue County—aphids were found on this plant. However.as a whole this field looked excellent and <br /> most fields where aphids were found were healthy and showed no observable damage. Considering the maturity of the <br /> zrop and the low abundance of aphids.treatment does not need to be considered for aphids in soybeans this season. <br /> • <br />