~This weeks blog is brought to you by Micheal Wier
When scouting, do not focus on aphid casts (white flecks) as these are just skin casts and not actual aphids.
It is just as important to scout for beneficial insects as these will control a large pop of aphids. Ladybug larvae and adults, lacewing larvae and adults, hoverfly larvae and adults, minute pirate bugs are all beneficial insects I have been noticing in the field. For example, ladybugs can eat up to 150 aphids a day.
A lot of the soybeans in the area are in the R5- R6 stage. As soybeans reach the R6 stage, it is believed the economic threshold increases so the soybeans need to have more soybean aphid than the traditional 250 aphids per plant. Soybean aphid populations can rapidly increase during the late R5 through R6 soybean growth stages and very high populations can sometimes be seen at the end of the season. Yield loss can occur as late as the early R6 growth stage. However, regular scouting of fields and use of the threshold of 250 aphids per plant through the R5 stage should prevent most, if not all, yield limiting aphid populations in R6. While the economic injury level for R6 soybean is not known, it is believed to be higher than earlier stages.
Consider scouting a more than once, assess whether a field is at threshold based on two visits (unless pressure is very high). It is easiest to assess the field, get a feel for aphid and beneficial populations, and then return 2 – 3 days later to see if aphid populations have increased or decreased.