Many different types of water weeds are found infesting the drainage and irrigation systems in south Florida, where a subtropical climate is very favorable for rapid growth.

Zimmerman has summarized the plant hormone activity of trichlorobenzoic acid and various substituted derivatives. The effects have been found to be formative in nature.

In Louisiana approximately 300,000 acres of sugarcane are grown each year for the manufacture of sugar. Another 125,000 acres are necessary for the rotation program, making approximately 425,000 acres devoted to the production of cane. Of these, 100,000 acres were estimated in 1950 to be so badly infested with Johnson grass (Fig. 1) that a control program was necessary to obtain economic yields of cane. In addition to this acreage, headlands, ditchbanks, and roadsides of many additional plantations were infested with Johnson grass and constituted a potential threat to the cane fields.

Several workers have reported that the activity of certain plant-growth regulators is influenced by the particular carrier employed in applying the materials to the plants. The compound 2,4-D is more inhibitory to Kidney bean plants when applied in a Carbowax 1500 aqueous solution than in wholly aqueous solution. The inhibitory effectiveness of oil sprays of 2,4-D is reduced little by rainfall whereas wholly aqueous sprays may be rendered almost noneffective by rainfall a few minutes after treatment. Rice has reported a greater amount of absorption of NH4 2,4-D by leaves when Carbowax 1500 is included in aqueous solutions than occurs when wholly aqueous solutions are employed. The results presented herein are from additional studies on the effects of different carriers and formulations on the inhibitory properties of selected plant growth-regulators.

The announcement of the effectiveness of Isopropyl N phenyl carbamate as a graminicide received considerable interest by weed research workers. However, early attempts to control grasses with this chemical resulted in rather disappointing control. Subsequent work has shown that this can be largely attributed to improper usage of the material. Since this material is supposedly a growth regulating substance, it was reasoned that it should behave in a manner similar to 2,4-D. Study carried on in Oregon proved that this was not the case and that specific conditions are essential to maximum effectiveness of this chemical.

The herbicides 2,4-D and 2,4,5-T are used extensively in the Western States for killing Ribes, the noxious plants that spread the destructive blister rust (Cronartium ribicola Fischer) to white pines (Pinus L.). Tests of the thermal fogging unit here described relate to the broadcast application of low dosages of 2,4-D as a wet oil-fog designed to defoliate and damage ribes plants without significantly damaging associated white pines. Tests were made at Stockton, and near Pescadero, Calif., in 1950.