costs of application very difficult. Constantly changing form- 
lations as well as methods of application have completely revolu- 
tionized the methods used. In the control of cotton insects, 
prior to 1946 the principal insecticides were calcium arsenate 
and sulfur, but during the period 1946-51 DDT, BHC, and sulfur 
predominated, although a number of other new insecticides were 
being introduced. Similar changes have been made on other crops 
and commodities. 
The cost of application of insecticides was evaluated in relation 
to the cost of the insecticides rather than on an acreage basis. 
About one-fourth of all insecticides used were on cotton, and it 
cost about hO cents to apply a dollar's worth. Fruit and cereal 
and forage crops required about one-fourth of all insecticides 
used, and the cost of application to these crops was about half 
the cost of the insecticides. The remaining insecticides were 
used under situations that called for higher application ccsts. 
On vegetables, greenhouse crops, stored products, livestock pests, 
and in the home, the cost of application was estimated to be 
nearly one and one-half times the cost of the insecticides. 
Cultural Control. = No data are available for estimating the 
amount expended for controlling insects by cultural or mechanical 
methods. Some of the cultural practices used by the grower are 
clean cultivation, stalk and trash destruction, crop rotation, 
planting resistant varieties, hand picking or hand worming, 
timing of planting dates, and screening. After harvest many pro 
ducts require special handling and grading to make allowance for 
insect damage and special storage or packaging to prevent infesta- 
tion. These practices add an appreciable amount to the cost of 
insect control. 
Biological Control. < The expense of utilizing natural enemies 
such as parasites, predators, and diseases as a means of combat- 
ing insects is berne chiefly by Federal and State agencies. In 
only a few instances-such as lady beetles for use against mealy= 
bugs and certain scale insects on citrus, the parasite 
Macrocentrus ancylivorus against the oriental fruit moth on 
peach, and milky disease spore dust against the grub of the 
Japanese beetle - have these biological agents been available 
commercially for use by private individuals. At least $500,000 
is expended annually in the biological control of insect pests, 
including the search for beneficial insects in foreign areas and 
importing them into the United States. 
Plant Diseases 
The production of a number of agricultural crops, particularly 
fruits and vegetables, requires spraying or dusting with fungi- 
cides for disease control. The production of apples, peaches, 
cherries, and certain vegetables in the humid sections of the 
country is impossible without protectant fungicides. Most of 
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