After the copper- sulfate -treated water has been in contact with the algae for 12 

 hours or more, empty the tank and give it a thorough cleansing. Treatment is only 

 temporary and may need to be repeated as algae or moss regrows . 



HERBICIDE USE AND CROP SAFETY 



Improper herbicide use may cause serious injury to crops or desirable plants . Three 

 factors to consider are drift, contaminated equipment, and excessive herbicide rates . 



Drift hazards. These are greatest when herbicides that affect the leaves of plants 

 are applied. These may be growth- regulatory herbicides, such as 2,4-D and silvex, 

 or contact herbicides, such as paraquat, the petroleum oils, and "dinitro." To re- 

 duce spray drift, use low pressure (10 to 30 p.s.i. for ground sprayers) and a noz- 

 zel with a large opening that gives a coarse spray. Do not spray if the wind is 

 blowing toward nearby, susceptible plants. 



Contaminated equipment . It is extremely risky to use spray equipment that has been 

 used for the phenoxy herbicides (2,4-D, silvex, and others) to spray susceptible plants. 

 Tomatoes, grapes, and red bud trees are especially sensitive. 



Whenever possible, it is best to have separate spray equipment to apply phenoxy her- 

 bicides. If it is absolutely necessary to use the equipment for other purposes, clean 

 it very thoroughly. The spray barrel or tank is the greatest source of contamination, 

 followed by the hoses. It is best to change the barrels and possibly the hoses; but 

 when this is not practical, we suggest the following steps to remove 2,4-D and relat- 

 ed materials from metal tanks : 



1. Add a small amount of water, and "slosh" it around in the barrel. Empty and re- 

 peat. Using kerosene or fuel oil helps to remove herbicides that are oil-soluble. 

 The ester forms of 2,4-D emulsifiable concentrates that form emulsions when mixed 

 with water usually are formulated in oil and are oil-soluble. Amine salts are 

 water-soluble and are generally easier to remove. Following an oil rinse, rinse 

 with a detergent in water several times to remove the oil. 



2. Rinse the entire system with water containing a wetting agent or a detergent. Re- 

 peat and flush part of the rinse through the sprayer, and empty the remainder. 



3. If the ester form of 2,4-D was used, fill the tank with water and household am- 

 monia at the rate of 1 quart of household ammonia to 25 gallons of water. Pump 

 enough solution through the hose and nozzles to completely fill those parts. 

 Then fill the tank, close it, and leave it for 24 hours. Rinse thoroughly with 

 water. [NOTE: Adding ammonia to equipment contaminated with 2,4-D does not 

 "inactivate" the 2,4-D. It converts ester forms of 2,4-D to water-soluble am- 

 monium salts. Then the 2,4-D salts must be completely washed out of the sprayer.] 



4. Activated charcoal is also useful for cleaning herbicides from spray equipment. 

 Usually, 2,4-D and similar herbicides can be removed fairly well by rinsing the 

 sprayer for about five minutes with a 0.3-percent suspension of activated char- 

 coal (1/4 pound of activated charcoal in 10 gallons of water containing a house- 

 hold detergent) . Drain and thoroughly rinse with clean water. Activated char- 

 coal can be obtained in 1-pound bags at some dry-cleaning establishments. 



To remove wettable-powder herbicides, first check to see that none of the material 

 remains caked in the bottom of the tank. A thorough rinsing with water and a deter- 

 gent is usually sufficient to clean the tank. Take screens and nozzles apart to be 



