The damage may be only slight, or the entire boll may ripen prematurely and become dry and dead.
Of this total no less than $40,000,000 (8,000,000) is credited to a small beetle, the cotton boll weevil, and to two caterpillars.
No certain remedy is known for the destruction on a commercial scale of the boll weevil, but every effort has been made in the United States to check the advance of the insect, to ascertain and encourage its natural enemies, and to propagate races of cotton which resist its attacks.
The boll worm is most destructive in the south-western states, where the damage done is said to vary from 2 to 60% of the crop. Taking a low average of 4%, the annual loss due to the pest is estimated at about 1 - 2,500,000, and it occupies second place amongst the serious cotton pests of the U.S.A. The boll worm is widely spread through the tropical and temperate zones.
The Egyptian boll worm (Earias insulana) is the most important insect pest in Egypt and occurs also in other parts of Africa.