Vol. 51—1997 - NorthEastern Weed Science Society

171
significant reduct:
cultivars are not'
of pounds of herbicides on the ground. However, the bromoxynilresistant
ly to be developedcommercially.
Althoughlweed control was excellent and althoughoverallyields were equivalent, the best
performing clon~s produced yields of U.S. Number One potatoes that were 70% to 85% of the
untransformed control. That's what's meant by testingfor horticulturalacceptability. U.S.
Number One poX'to yields are a very important characteristic. Because the transformedcultivars
don't perform as well at producingU.S. Number One's, there is no commercialinterest in
pursuing this her icide resistantcultivar.
I,
There3' some other constraints on herbicide use in vegetables. One of the constraintsis
the use of compl x rotations in vegetable production. Vegetablegrowers have to use chemicals
that have residu action very carefully lest a rotationalcrop is damaged. If vegetablesare
transformed to tt'lerate certain herbicides, then the resistancewill have to be developedfor a
majority of vege ble crops so that rotational flexibilityis not constrained. Complex rotationsare
a major limitatio and considerationin vegetableherbicideuse.
Another fonstraint on the use of herbicidesin vegetableproductionis the tendencyof
certain vegetable crops, such as peas, watermelons. tomatoes and potatoes to become weeds in
the following cropping season. This may result in a major weed problemif the weedy vegetable
was resistant to E' e herbicides that are used in the followingcrop. This is the downsideof
developing resis ce to the same herbicidein many vegetablecrops. On the one hand, rotational
flexibility is not, onstrained. On the other hand, it may complicatethe problemof weedy
vegetables. i
One possibility in the future is that genetic engineeringwill becomeroutine and
inexpensive. It JIOaybe the case that genetic engineers will be able to routinelyinsert any genetic
characteristics ~ey want in any cultivar at low cost It's really too early to tell if this will happen,
but it might andIthe routine-ness could lead to new herbicideresistantcultivars for vegetable
crops. ,
The developmentof herbicideresistantsoybeanshas implicationsfor minor use crops.
Some weed scientists worry that the increased use of glyphosatein soybeanswill result in a
decreased use fqr some currently used herbicides that are also currentlyused by vegetable
growers. Thetcdncem is that if the soybean market declinesfor some of these herbicides, they
may become un rofitable to produce and be voluntarilywithdrawnfor soybeans and for vegetable
crops as well. . at happened with chloramben. One inadvertenteffect of herbicide resistant
soybeans may be the loss of herbicidesfor minor crops.
On the Jther hand, it might lead to the exact opposite result If glyphosate use on
soybeans leads tothe reduced use of other soybean herbicides,the labels for those herbicides
might be expan~ed to include more minor uses. Afterall, if the soybeanmarket is decliningfor an
herbicide, it wo ld make sense for the manufacturer to look around for other markets for
expansion. Wi. numerous herbicidesbeing used in soybeans.manufacturersmay exhibit more
interest in the minorcrop market. Thus. an inadvertenteffect of herbicideresistantsoybeans may
bethe eXPansiar of herbicide labels for minor uses. It's too early to tell.