Soybean Aphids are Starting to Colonize Soybeans

Scouting efforts on June 6, 2008 found a low incidence of aphids in one field (3 aphids on one plant in 100 examined). This field in Arva was planted early and has reached the first trifoliate stage. Scouting of other fields in the area did not detect the presence of soybean aphids in any other fields. Overall the incidence of soybean aphids to date is low in Ontario but early planted fields should be scouting in the next few weeks to ensure that SBA populations do not increase in these fields. The field found today in Arva was directly across from a plot that last year was colonized with SBA by May 10th and was sprayed by June 11th last year because the aphid population had reached threshold. The observations made today indicate that we are no where close to what we experienced last year but is more typical of a normal year when populations are noticed on soybeans near second week of June (9th -14th) time period. The most likely source for these aphids is from buckthorn in the area (local) and not dispersal from distant locations (wind). Michigan State University (Chris DiFonzo) has also found a site with soybean aphids on plants but the Michigan site has a much higher incidence (60% of plant infested with soybean aphids).

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