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Late Season Soybean Aphids (08/31/17)

Soybean aphid infestations near the economic threshold (E.T.) of 250 aphids per plant and 80% incidence have been reported in some soybean fields in the R6 (full seed set, green seed that fills pod in one of four uppermost nodes) in southeast North Dakota.

Late Season Soybean Aphids

Soybean aphid infestations near the economic threshold (E.T.knodel.1) of 250 aphids per plant and 80% incidence have been reported in some soybean fields in the R6 (full seed set, green seed that fills pod in one of four uppermost nodes) in southeast North Dakota. However, most fields do not have increasing aphid populations now, a critical part of the E.T. With our shorter, cooler days, soybean aphids are migrating around more to find later planted soybean fields (with younger plants in R4 or R5) or starting their migration to their overwintering host, buckthorn. This is the sexual part of the reproduction cycle and usually starts in late August and continues into September. If you are seeing a lot of winged aphids or white dwarf aphids, I would definitely not recommend any treatment. Remember to count only healthy Mountain-dew colored aphids for the E.T (don’t count the white dwarf aphids). Lots of winged aphids indicate that they are ready to move out and will not feed much longer on your soybeans.

More beneficial insects are present in soybean fields now. If you are seeing a lot of beneficial insects, this is another good reason not to spray. With the recent rains, it is easy to find fungal infected soybean aphids in soybean fields.

Research indicates that there is not a yield benefit for treating soybean aphid as the soybeans reach R6 and later crop stages.

 

 

 

 

 

Janet J. Knodel

Extension Entomologist

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