Volume
2 Issue 2 May
25, 2005
Cut The Cutworms!!
 There
have been multiple reports of cutworms in sugarbeet in the
last week and even with the unseasonably cold temperatures
earlier in the month, they’re appearing pretty much on
schedule. Both Red-Backed and Dark-Sided cutworms occur in
the Red River Valley and both have similar life cycles.
They both over-winter as eggs laid by the moths in
cultivated fields at the end of summer. The following late
May/early June, the eggs hatch and the caterpillars move
onto seedling crops.
Scouting - Cutworms feed mostly in the evening
and at night and so are difficult to locate in the
daytime. Their feeding causes wilting, death and
occasionally they’ll cut the entire seedling off near
ground level. Scouting for these worrisome worms is best
done by looking for wilting or dying plants and then
looking in the top 1”-2” of soil at the base of these
plants.
Thresholds & Treatment – An economic return on
treatment can be expected when 4% - 5% of beets seedlings
are cut in a field. Pesticides are best applied in the
evening resulting in high levels of insecticide present
during the cutworms’ period of greatest activity. In
addition, in the evening the canopy will tend to have
higher humidity and perhaps some dew to carry the
insecticide over the plant surfaces in greatest danger of
feeding damage. For the same reason, liquid formulations
tend to be more effective against cutworms. To assist in
delivering the insecticide to the caterpillars, break up
severe soil crusting prior to, or during application. Some
insecticides registered
for use against cutworms in sugarbeet
are listed in the attached table
(remember to always check the label for registration
details).
Ian MacRae, U of MN Extension Entomologist
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