Volume
3 Issue 5
June
20, 2006
Soybean Aphid Finds Begin to Start
Some Early Heartburn
Well, lots of concern being expressed about some of the
early finds of soybean aphid through the region. Though
these early infestations should grab our attention, it is
more for alerting and preparing us for future concerns
rather than beginning management programs.
As one scouts fields and observes any soybean aphids,
keep in mind the concepts of Severity and
Incidence. They work together to describe what
is happening on average in a field. We could have some
heavily infested plants (high severity), but they are rare
(low incidence). OR, we could have low numbers of aphids
(low severity) but it is common (high incidence). Or, we
have some other combination in between. You still must
determine,
“What is the average?”
What we expect to happen is to get to a point in time
(late vegetative to R1) where we know 250 aphids per plant
is a reliable threshold. Then the speed scouting approach
will be helpful since it is designed to guide us on our
management decisions at that stage.
With what we know so far about soybean aphid, we
realize these early colonizations are NOT a
guarantee of treatable populations later. Allow our
predators and parasites to establish with these early
populations. They assist in stabilizing populations early.
If we kill the good guys early with unnecessary
insecticide treatments, conditions may develop where the
natural enemies of soybean aphid are not there to help
suppress aphid populations later.
Phillip Glogoza
REE - Crops, Moorhead
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