North Dakota State University Extension Service - Burke County
Burke County AgAlert
July 17, 2007
Banded Sunflower Moth—It’s back!
The banded sunflower moth occurred in high populations in the north central part of the state in 2006, and early reports of populations indicate that 2007 populations may be just as high. Growers and consultants in Bottineau and Renville County are reporting confection sunflower fields that have already met economic thresholds.
What is the economic threshold?
First of all there are two methods of scouting for banded sunflower moth (BSM).
One is egg sampling; the other is adult moth sampling. The adults are
currently emerging from overwintering sites and moving to this years
sunflowers to deposit eggs on sunflower bracts, where they prefer the
mid-bud stage. Egg, or adult moth sampling require looking at 20 or 100
sunflower buds, respectively, from 4 different locations in the field. Eggs
are very small, white to orange in color, and may be difficult, but not
impossible to see with the unaided eye. Examine 6-bracts on five plants at
each of 4 locations within the field. Thresholds are based on 1) cost of
control 2) plant population and 3) market price. A calculator is available
online at www.ndsu.nodak.edu/entomology/econ_calc.xls. To give you an idea
of what egg thresholds may be, a field with 20,000 plants per acre, while
market price is $0.13, and treatment cost of $9/acre would be 4-5 eggs per 6
bracts. The higher the cost per treatment, the higher the threshold would
be, in contrast the higher the market value or population, the lower the
threshold would be.
Sampling
for adult moths also occurs at the late bud (R3) stage. This method involves
examining 20 plants in 5 locations in the field, a minimum of 75 to 100 feet
from the edge of the field, for a total of 100 plants. The adult moth is
about ˝” long, light colored with a band across its back. Again thresholds
are calculated on various factors, but using the same example from above,
the adult threshold would be 1.3 adults per 100 plants.
Chemical Control Timing
Once you’ve established whether or not an insecticide treatment is
warranted, the proper timing is not until the R5.1 stage, when the ray
flowers or obvious and pollen shed is just beginning. This is a critical
period while the larva are present, but the plant has not formed seeds yet.
This is when larva are most susceptible to an insecticide. Once the plant
has formed seeds, the larva will be feeding within them, and protected from
the insecticide. Early egg laying, in years like 2006, or this year, may
warrant earlier applications. For more information on the sampling methods
and thresholds, or control measures, refer to your 2007 Field Crop Insect
Management Guide.
Dan Folske
Extension Agent/Burke County
Soil Conservation Technology Specialist
PO Box 280
Bowbells, North Dakota 58721
dan.folske@ndsu.edu
701-377-2927