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THE GYPSY MOTH 
( Porthetria dispar (L.)) 
is a serious pest 
Be trp es in New 
England and eastern New York 
State. The caterpillars, or larvae, 
of these moths eat the leaves. The 
defoliation retards the growth and 
otherwise weakens the trees, and 
repeated complete defoliation will 
permanently injure or even kill 
them. 
This moth was accidentally in- 
troduced into this country near 
Medford, Mass., in 1869. It 
spread rapidly through several of 
the Northeastern States. For many 
years the infested area has been 
under Federal quarantine. In part 
of this regulated area suppressive measures are being carried out in co- 
operation with State and local agencies. 
The gypsy moth larvae usually appear about the first of May. They 
increase in size until by the middle of June they are iy 2 to 2 inches long. 
They can then be recognized by several pairs of red and blue dots on their 
backs. Late in June or early in July they become mature and seek shady 
places, such as on trees or rocks, in which to pupate, or transform into moths. 
The moths emerge about a month later. The males are strong daytime 
fliers, but the females cannot fly and so lay their eggs close to the place where 
they issued as moths. The eggs are laid in clusters of 400 or more, which 
are covered with brownish hairs. The winter is passed in the egg stage. 
Control 
The gypsy moth can be controlled most effectively with DDT. An oil 
solution or an emulsion containing this insecticide is applied as a spray 
while the insect is in the caterpillar stage. Large forested areas are usually 
sprayed from aircraft. For use along highways and residential areas either 
mist blowers or hydraulic sprayers are suitable, and for treating low growth 
along stone walls and fences sprayers of the knapsack type can be employed. 
Early in the season the spray should be applied at the rate of 1 pound of 
actual DDT per acre, but after the foliage has developed % pound per 
acre is sufficient. Information on formulations and dilutions to use with 
each type of equipment may be obtained from the Division of Gypsy Moth 
Control, Bureau of Entomology and Plant Quarantine, Greenfield, Mass. 
CAUTION. — DDT is poisonous and should be handled with care. 
Store in a dry place where children and animals will not have 
access to it. 
☆ u. S. GOVERNMENT PRINTING OFFICE: 1950 
November 1950 
For sale by the Superintendent of Documents, U. S. Government Printing Office 
Washington 25, 1). C. - Price 5 cents 
913859°— 50 
