Minnesota Crop News > 2001-2008 Archives
First Soybean Aphids of the Year
Ragsdale, Ken Ostlie, & Ian MacRae, Dept. of Entomology, University of Minnesota
aphids have been recovered this week from both soybeans and
buckthorn at the Rosemont Research & Outreach Center.
This is the earliest that soybean aphid has been collected
from soybean in Minnesota. Plants at Rosemont are mostly
in the VC stage, just emerging from the ground, to V-1 (first
true leaves). In addition, colonies of soybean aphids were
found on buckthorn bordering fields on the St. Paul campus.
Surveys in the NW part of the state have not indicated the
presence of soybean aphid yet, nor have they been found in
SWROC in Lamberton according to Bruce Potter.
not necessarily cause for concern. Early appearance doesn’t
necessarily indicate early problems in commercial fields;
much depends on how well the colonies become established
and how quickly they grow in number. Weather conditions across
the state are generally favorable for aphid reproduction
at the moment but there are chances for showers and thunderstorms
in most of the state by late in the week. In addition, establishing
aphid populations are very susceptible to predation and there
is an abundance of ladybird beetles observed in soybean fields
so aphids may never reach damaging levels.
thresholds for soybean aphids are 200-250 aphids per plant
with more than 80% of the plants with a population that is
still on the increase. It is not advisable to treat aphids
before they reach treatment thresholds, especially early
in the season. At this point even using insecticides with
longer residual activity against aphids will not eliminate
the risk of re-infestation later in the season. Populations
may also come under natural control and not require subsequent
treatment. Scouting is the key.