Rotary hoeing can help control early weeds and aid soybean emergence, especially if 

 the soil is crusted. The rotary hoe is most effective after weed seeds have germi- 

 nated, but before the majority of the weeds have emerged. Operate the rotary hoe at 

 8 to 12 miles per hour. Add enough weight to stir the soil and to kill the tiny weeds. 



Dinoseb , sold under several trade names including Preemerge Dinitro Weed Killer and 

 Sinox PE, is cleared for EARLY postemergence use- -when the soybeans are still in the 

 cotyledon stage. Do not apply dinoseb if the first leaves have opened to expose the 

 terminal bud or if the soil surface is moist. If you do, severe soybean injury could 

 occur . 



Dinoseb is primarily a contact herbicide used to control broadleaf weeds. It does not 

 control annual grasses well, and gives little residual control of seedlings that germi- 

 nate after application. Dinoseb is cleared for tank-mixing with Amiben or Lasso, and 

 is also packaged with Alanap (as Dyanap, Ancrack, and Kleenup) to improve residual con- 

 trol. 



To control cocklebur, morningglory, and the like, dinoseb or "dinitro" may also be used 

 as a directed-postemergence treatment when soybeans are 5 inches high up to the bloom 

 stage. However, special directed- spray equipment is needed in order to minimize con- 

 tact with the soybeans. 



The rate of dinoseb varies from 2 to 3 quarts per acre, depending on the air temper- 

 ature. Use the 3-quart rate when the maximum air temperature is below 75° F. ; the 2- 

 quart rate, when the maximum air temperature is 75 to 96° F. Do not apply dinoseb if 

 the maximum air temperature within 24 hours is expected to be over 95° F. Be extreme- 

 ly careful when using dinoseb. It is quite toxic to man and animals. 



Chloroxuron , sold under the tradenames of Tenoran and Norex, can be applied after tri- 

 foliate soybean leaves form and when broadleaf weeds are less than 2 inches tall. Chlor- 

 oxuron will control most annual broadleaf weeds in soybeans. Velvetleaf control is 

 erratic, however; and do not expect grass control. Soybeans usually show some tempor- 

 ary injury, but that usually will not reduce yields. 



The broadcast rate for chloroxuron is 2 to 3 pounds per acre of Tenoran 50W or Norex 

 50W, plus 1 pint of a suitable surfactant per 25 gallons of spray. Use proportionate- 

 ly less for directed or semidirected sprays. A nonphytotoxic oil can be used at a 

 rate of 1 gallon per acre instead of the surfactant with directed or semidirected sprays . 



2,4-DB amine formulations are sold under the tradenames of Butoxone SB and Butyrac 175 

 for postemergence control of cocklebur in soybeans. 2,4-DB may also give some control 

 of morningglory and giant ragweed. It can be broadcast over the top of soybeans from 

 ten days prior to bloom until midbloom. Expect some soybean injury, such as leaf wilt- 

 ing, stem curvature, and possible stem cracking. Lodging may be increased and yields 

 may be reduced under unfavorable conditions. Consider 2,4-DB for emergency control 

 when the benefits from weed control will overshadow the risk of soybean injury. 



Directed sprays may reduce the severity of injury. 2,4-DB can be directed when soybeans 

 are at least 8 inches high and cockleburs are less than 3 inches tall , if this height 

 difference occurs. Do not spray more than the lower third of the soybean plant. And 

 do not apply 2,4-DB if the soybeans show symptoms of Phytophthora root rot disease or 

 if the soybeans are under drought stress. 



CORRECTION 



Last week in the paragraph under weed control in flooded areas, the rate of paraquat 

 was stated as 1/2 pint. This should have been 1 to 2 pints. 



