-4- 



The following is a summary of a recent report on research given at the Weed Science 

 Society of America: "Low per-acre dosages of surfactants which would result from 

 normal spray- additive concentrations applied in the field appeared to have little or 

 no effect on the distributional rate of herbicides in soil profiles following irriga- 

 tion. Conceivably, however, intentionally higher levels of surfactant might be used 

 to enhance or retard the movement of both herbicides and water in soils, according 

 to design and purpose." 



For postemergence applications, some adjuvants or surfactants may increase the ef- 

 fectiveness of some herbicides by providing a more complete coverage of the leaf 

 surface, lengthening the time of contact, or increasing the degree of penetration. 

 An additive that improves weed kill though may also increase crop injury. 



Herbicide formulations often contain certain oils and surfactants. Adding addi- 

 tional amounts may be unnecessary, costly, and unwise unless suggested specifi- 

 cally on the herbicide label. 



Several field studies with various additives indicate that the nonphy to toxic crop 

 oils, as recommended on certain labels, have been more effective for weed control 

 than products originally intended for use as household detergents. It is usually 

 advisable and often more economical to give preference to agricultural surfactants. 



Compounds for which "no economic poison" claims are made do not have to be reg- 

 istered with EPA under the Federal Insecticide, Fungicide, and Rodenticide Act. 

 But the EPA says, "No surfactants, crop oils, or other additives should be mixed 

 with any herbicide unless such a mixture is specified on the herbicide product 

 label or labeling." 



In summary, we do not recommend adding "soap" to herbicides. 



PLANT DISEASES 



SEED EMERGENCE PROBLEMS OF SOYBEANS 



Soybean seed that is injured by machinery at harvest or during processing or plant- 

 ing may not emerge well. Seeds that are too dry or too wet may be split or cracked 

 or may have other wounds. Seedling growth is slow- -especially in cool, wet soil. 

 Seed rot and damping-off organisms, such as Pythium, Rhizootonia, and others, read- 

 ily infect seeds and seedlings through wound areas. The result is a thin, uneven 

 stand with numerous yellowed shoots. Do not plow-up the stand unless there are 

 large gaps or areas where there are no plants. 



LOOSE SMUT OF WHEAT AND BARLEY 



Loose smut of wheat and barley caused by Ustilago tritiai and U. nuda has been ob- 

 served in both barley and wheat this year. Damage levels depend on conditions at 

 flowering time. Cool, humid weather favors the infection of flowers in healthy 

 heads. After the fungus has infected the female parts of the flower and pene- 

 trated the seed embryo, it becomes dormant until the seed is planted the next sea- 

 son. 



The fungus grows systemically within the barley or wheat plant. The apparent in- 

 fection level (the number of black, smutted heads) in any one season is the result 

 of infections that occurred during the previous year. Control measures include 



