INSECTICIDES AND EQUIPMENT FOR CONTROLLING INSECTS 39 



Do not practice the old maxim "If a little is good, more is better." 

 Excessive quantities of wetting agents may increase the run-off of 

 the spray and thereby actually decrease the efficiency of the ma- 

 terial. Excessive quantities of insecticide in the spray greatly 

 increase the cost and may injure the plants as well as waste strategic 

 materials. 



As sold by dealers in garden supplies, many spray preparations 

 contain the essential ingredients in concentrated form, ready for dilu- 

 tion with water and application to plants. Where only small quan- 

 tities of insecticides are required, it may be more practical to use 

 such prepared spray or dust mixtures than to purchase the ingredi- 

 ents separately. The latter procedure is usually more economical 

 in commercial practice where large quantities are used. It may be 

 possible for gardeners to make group purchases of insecticides in 

 larger quantities at lower prices and to mix dusts cooperatively. 

 Such procedures save in cost of materials and time. 



If proprietary insecticides are used, select those labeled to show 

 the active ingredients. Reliable companies have usually tested their 

 products sufficiently so that confidence can be placed in their rec- 

 ommendations. 



A set of measuring spoons, measuring cups, and a gallon measure 

 calibrated in pints and quarts should be provided for accurately meas- 

 uring the materials. Larger utensils are of course required if con- 

 siderable quantities of insecticide are to be applied. Such utensils 

 should be retained for this purpose only. 



The chance of error is greater in measuring dry materials than 

 in measuring liquids because of differences in compactness and density 

 of different brands. Whenever possible the quantities of dry in- 

 gredients should therefore be determined by weight. Before meas- 

 uring a dry ingredient in small quantities, free it of lumps and com- 

 pactness by stirring or screening. After filling the measure, scrape 

 off the excess with a straight-edged piece of wood, such as a pot 

 label. 



QUANTITY OF SPRAYS OR DUSTS TO APPLY 



Table 1 gives information on the quantities of liquid insecticides 

 and dusts, such as lead arsenate, calcium arsenate, derris, nicotine 

 sulfate, and other materials, that are necessary to treat row crops 

 at the different rates per acre. Normally an acre of crop grown in 

 rows, such as beans, potatoes, cabbage, and similarly grown plants. 

 requires from 75 to 150 gallons of liquid spray, depending on such 

 factors as the nature of the crop, the size of the plants, and the thick- 

 ness of the growth or stand. On an average, however, from 100 to 

 125 gallons of liquid spray will cover the plants in an acre satis- 

 factorily. For small gardens at this latter rate about V/ 2 to 2 quarts 

 of liquid spray is needed to cover 50 feet of row for each application. 

 Information is also given on the number of feet of row that 1 gallon 

 of spray will cover at application rates ranging from 75 to 200 gallons 

 per acre. 



With reference to the application of insect icidal dusts, an acre 

 usually requires from 15 to 25 pounds per application, with an average 

 of about 20 pounds. The variation is subject to the same factors 

 as to crop, size of plants, thickness of the stand, and nature of the dust 



