How much money do Americans spend on pest control each year?

The EPA website has lots of information on the market for pesticides,
albeit a little dated:

"The pesticide industry is quite significant in dollar terms. Annual
expenditures by users of pesticides totaled $11.9 billion in 1997
(conventional pesticides plus sulfur, etc.). Of this, 70 percent was
for use in agriculture (a total of $8.3 billion — an average of nearly
$4,400 per farm in the U.S. — 1.9 million farms). The U.S. total of
$11.9 billion equals $44 per capita. The average U.S. household spent
about $20 for pesticides applied by the homeowner. (This does not
include expenditures for pesticides applied to homes and gardens by
others for hire.) The U.S. accounts for nearly one-third of pesticide
user expenditures world wide."
http://www.epa.gov/oppbead1/pestsales/97pestsales/intro.htm#overview

Follow the above link for more detailed information and tables of data
for 1996 and 1997.