POMULOGICAL RESEARCH 

 13. Chemical Control of Weeds in Fruit Plantings 



The use of chemicals to control weeds is not new. Such ordinary materials 

 as salt and smelter wastes have been used for centuries • The modern era of chem- 

 ical vfeed control began with the accidental discovery of the selective action of 

 copper salts in I896, During the period from 1900 to World War II a considerable 

 list of weed killing chemicals was developed. Some vrere selective, some weare norw 

 selective and a few could be used as soil sterilants. Large quantities of a few 

 of these were used for specific purposes, mostly in the western states. 



With the entry of the United States into World Y[ar II and the consequent 

 shortage of labor, chemical weed control began to receive more attention as a 

 labor saving device. The introduction of 2,U-D with all the possibilities it 

 presented stirred the imagination of manufacturers, researchers, farmers and other 

 users. The public press and trade papers kept before consumers a rosy picture of 

 the performance of this "miracle" weed killer. 



Although 2,U-D has not solved all weed troubles, it is a very useful material 

 Virhere it is adapted. It also focused attention on the possibilities of a much 

 wider use of chemicals for weed control. The result has been a deluge of new 

 chemicals with supposed weed killing potentials, llany of these vrere distributed 

 to researchers before their real value was known. Therefore, the researcher v;as 

 faced witn the task of "weeding" the weed killers. Among so many herbicides there 

 certainly should be some that could be used to advantage in fruit plantings. 



One of the first to be used in orchards was sodium chlorate, formulated to 

 reduce fire hazard, to control poison ivy^ This was largely replaced by aiiimonium 

 8ulfamate (Ammate), Ilore recently 2,U-D, 2,U,5-T, and mixutres of the tv/o have 

 come into wide use. Directions for poison ivy control are in Special Circular 190, 

 Poison Ivy, Thj^se materials are being used also for the control of brush around 

 orchards. The control of choke cherries, a menace to nearby peach orchards, is 

 discussed in Special Circular 216, Choke cherries; Hm to Recognize and Get Rid 

 of Them, 



Soon after the introduction of 2,U-D it was found that straviberry plants would 

 tolerate more than many of the vfeeds associated with them. The optimism generated 

 was short-lived. Although the strawberry plants themselves would tolerate 2,U-D 

 applications, runner and fruit bud formation and fruit growth were adversely 

 affected. Hence, 2,U-D's usefulness in strawberry fields is so Umited it is not 

 included in our chemical -weed control recommendations for this fruit. Numerous 

 other materials have been tried but only two are recommended, SES for control of 

 summer weeds and CIPC for winter weeds, especially chickweed. Consult Special 

 Circular 215, Chemical Vfeed Control in Strawberries, for details, 



ilature raspberry canes are fairly resistant to 2jU-D which can be used at 

 1-1/2 pounds amine form per acre to control broad leaf weeds after suckers are two 

 feet high, SFS vail delay the reappearance of weeds when applied at 3-U pounds 

 per acre to a weed-free field. CIPC at 6-8 pounds per acre applied from mid-October 

 to mid-November vdll control winter weeds, TWo applications a month apart may be 

 made if necessary. Except during suckering DNBP may be used at 3 pounds per acre 



