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Soybean aphid update

Scouts working throughout Minnesota between July 19 and August 2 encountered soybeans in reproductive growth stages ranging from beginning bloom to beginning seed (Figure 1).  Spring rains delayed planting throughout other regions of the state, delaying crop growth and development.

Figure 1. Soybean growth stages in scouted fields from July 19 through August 2, 2019. Map: NDSU Extension IPM.

Aphid incidence

Aphid incidence remains low throughout surveyed fields in the northwest (Figure 2).  The percentage of aphid infested plants in southeastern Minnesota was higher with more locations reaching up to 50 or 79 percent infestation.
Figure 2. Soybean aphid infestations or the percentage of plants infested with soybean aphids at each location scouted. Map: NDSU Extension IPM.

Average number of aphids per plant

While the percentage of plants infested has crept higher in some fields, the average number of aphids per plant remains 20 or fewer (Figure 3). 
Figure 3. Average number of soybean aphids per plant in scouted fields. Map: NDSU Extension IPM.
As soybean growth and development continues to progress there is still time for soybean aphid populations to increase to threshold densities before soybeans outgrow risk. This is why scouting is recommended until soybeans are well into the R6 (full seed) growth stage.

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