This graph shows the gypsy moth defoliation in Ontario from 1981 to 2004, based on aerial surveys by the Canadian Forest Service.

• The total area of defoliation caused by the gypsy moth increased from 1981 to 1985. In 1985, the total area of defoliation was almost 250,000 ha.
• The total area of defoliation decreased from 1985 to 1987, when it dropped to about 15,000 ha.
• The total area of defoliation increased from 1987 to more than 75,000 ha in 1989, decreasing slightly in 1990 and then climbing to 350,000 ha in 1991.
• The total area of defoliation fell to less than 50,000 ha in 1992 and then remained under 25,000 ha from 1993 until 2002, when it climbed to more than 150,000 ha.
• The total area of defoliation caused by the gypsy moth in 2004 was  411 ha.