Doug Johnson, Extension Entomologist
2013 is one of those transitional years for changes in
refuge requirements for transgenic control traits in field corn. Several
changes have been made over the last several years and one can expect for
changes to continue as we (likely) move away from large structural refuges and
toward refuge in a bag. Generally the % of refuge seed (those seed without
transgenic insect control traits) has dropped from 20% to 10% or even 5%
depending upon the traits included and the company. In addition those products
that require separate structural refuges
(usually as blocks or a series of rows) is giving way to the inclusion of not
traited seed within the bag of traited seed; the so called refuge in a bag
(RIB). The result is a somewhat confusing situation where products are
available that contain different refuge requirements. Obtaining the desired
corn genetics which contains the correct transgenic traits to control the
likely pests and planting this with the correct refuge in the proper location
can be very confusing.
If you follow the link:
http://pest.ca.uky.edu/EXT/Recs/ENT16-Field%20corn.pdf
, it will take you to ENT-16, the 2013
Insecticide Recommendations for Corn. On pages 6 and 7 of this publication you
will find a Bt Trait Table that list the various packages of transgenic insect
control traits by trade name, insect toxins, and the event used to include the
toxins in the corn plant. This table also includes relative ratings for how well
these toxin packages works against the most common and important insect pests
of field corn in Kentucky. Additionally, the type (block vs RIB) of refuge and
the percent of non-traited seed required to be in the refuge.
In Kentucky producers can expect their greatest and most
consistent return on investment from protection against European corn borer
(ECB) and southwestern corn borer (SWCB). Traits for control of western corn
rootworm (WCRW) are not needed nor recommended in corn fields that are rotated with
non-corn crops. Corn that is not rotated (continuous corn) should be planted
with products that contain more than one or “stacked” western corn rootworm
(WCRW) traits. In any case products containing only the Cry3Bb1 corn rootworm
toxin should not be planted in non-rotated corn. Though not yet noted in
Kentucky, this is the trait for which resistance has been show in several
states to our north. So far this has only occurred in corn planted in the same
field for three successive years and using only the Cry3Bb1 trait for
protection against western corn rootworm. Black cutworm (BCW), corn earworm
(CEW) and fall armyworm (FAW) infestations are very much dependent on the
growing year. Very early planting may benefit from BCW traits while very late
plantings will likely benefit from control of corn earworm and fall armyworm.
