Vol. 51—1997 - NorthEastern Weed Science Society

149
One of the
recent years
cultivar tole
recently has
with enhanced
astronomical
herbicide wit
environmental
to that herbi
IMPACTOF HERBICIDE-TOLERANTGERMPLASMON
PRODUCTIONANDMANAGEMENT OF ROWCROPS
A. C. York l
most interesting and significant developments in weed science in
s herbicide-tolerant cultivars (HTC's). Although differential
ance to herbicides is well documented in the literature, only
here been a conscious effort to develop lines of agronomic crops
tolerance to herbicides. Much of this can be attributed to the
ost of developing and registering new chemistry. If one has a
good activity on a number of problem weeds and good
attributes, it may be more practical to adapt additional crops
ide rather than developing new herbicides.
HTC's can e developed using standard selection and backcrossing
techniques. xamples include sulfonylurea-tolerant soybean [Glycine max (L.)
Merr.], imida olinone-tolerant corn (Zea ~ L.), and corn tolerant of
sethoxydim {2 [1-(ethoxyimino)butyl]-S-[2-ethylthio)propyl]-3-hydroxy-2­
cyclohexen-l- ne}. HTC's also can be develoPed via genetic engineering
techniques. xamples include cotton (Gossypium hirsutum L.) tolerant of
bromoxynil (3,S-dibromo-4-hydroxybenzonitrile), soybean and cotton tolerant of
glyphosate [ phosphonomethyl)glycine], and corn and soybean tolerant of
glufosinate [ -amino-4-(hydroxYmethylphosphinyl)butanoic acid].
HTC's hav the potential to significantly impact row crop production,
although it's too early to fully appreciate the potential long-term impacts
as there are any factors that can come into play. However, one can speculate
on some of t e short-term impacts. Impacts obviously will depend upon how
well HTC's a e accepted by growers. That in turn will depend upon the value
these cultiv rs bring to the grower. Hence, perhaps the best way to speculate
on potential impacts of HTC's is to consider the value or benefits they can
offer and ho they can improve weed management systems •.
One obvio
are difficul
current tech
options to c
growers addi
manages cert
in corn is a
in a corn cr
rotation wit
glyphosate-t
in the corn
Perennial br
hemp dogbane
increasingly
systems. Th
currently is
tolerant soy
these perenn
Another 0
crop injury
give growers
risk of crop
Irwin and Ba
is a major p
s impact of HTC's will be additional options to manage weeds that
to control or perhaps cannot be controlled in some crops with
oloqy. Compared with horticultural crops, there are a number of
ntrol most weeds in agronomic crops. However, HTC's may give
ional options to manage weeds or increased flexibility in how one
in problems. Common bermudagrass [Cynodon dactylon (L.) Pers.]
example. Bermudagrass currently cannot be adequately controlled
p although there are options for control in most crops grown in
corn or with post-harvest treatments. With sethoxydim- or
lerant corn, growers will have an option to control bermudagrass
rop itself rather than having to do it in a rotational crop.
adleaf weeds such as common milkweed (Asclepias syriaca L.) and
(Apocynum cannabinum L.) also are examples. These weeds are
becoming problems as growers move more into no-till cropping
se weeds can be controlled or suppressed in corn, but there
little that can be done to control them in soybean. Glyphosateean
will give growers an option to control or at least suppress
als in a soybean crop.
vious impact of HTC's will be effective weed control without the
ometimes associated with current control programs. HTC's will
an opportunity to control problem weeds without having to accept
injury. An example might be sicklepod [Senna obtusifolia (L.)
neby) in soybean. Across the Southeast and Mid-South, sicklepod
oblem in soybean. No currently available soil-applied herbicide
NC
lprof.~ Dept. of Crop Science, North Carolina State University, Raleigh,
27695-7~20.
I1
I
I
I
I
I
I
I
1
I
I
1
I1
I