Sexual sterilization is receiving much current attention because of its potential 
use as a new method of control. The effectiveness of releasing males sterilized by 
gamma radiation was established in the mid-1950’s when they were used to 
eradicate the screwworm, Cochliomyia hominivorax (Coquerel), from Curacao, 
West Indies, and from the southeastern portions of its range in the United States. 
The principles of sexual sterilization of insects are discussed in several papers (676, 
677, 678, 679, 680). Several authors reported the research that led to the method 
and its use against the screwworm (/79, /S0, 18/1, 734, 735). Research on the 
sterilization of some important forest insects has not been promising (5/, 637). 
However, in new work on the gypsy moth, use of the sterile-male technique with 
wholly or partially sterile males, shows good promise for eliminating isolated 
populations. Partially sterile males produce sterilized F, generations (/073). Further 
research must be conducted before the full possibilities of using the sterile-male 
release technique for forest insect control can be determined. 
Chemically induced sterility also offers promise as a control measure. The 
appropriate chemicals are called chemosterilants because of their capacity to de- 
prive insects of the ability to reproduce (/39, /0/8). Most of the chemosterilants 
that offer promise for practical control are mutagenic and can be used only in ways 
that will avoid all contact between them and nontarget animals (907). Chemo- 
sterilants may be added to the insects’ food or applied to surfaces to which the 
insects are attracted. Those mixed with food appear to produce maximum effective- 
ness and minimum hazard. So far, none is available for use in forest insect control. 
Insect repellents can be useful alternatives to the use of chemical insecticides. 
Considerable research, development, and use of repellents is associated with insects 
and related animals of importance to public health. However, relatively little 
emphasis has been placed on insects that damage trees or their products. 
Tests of organotins indicate that they deter feeding by the pales weevil (//97). 
Certain products of the neem tree also show deterrent capability (/82, 708). Pine 
oil, a by-product of sulfate pulping, shows promise as a repellent of several 
Dendroctonus spp. (931). 
Insect attractants are being given increased research attention to improve or 
reduce the cost of surveys and to open up new opportunities in integrated pest 
management of forest insects (99, 1/86). Some of these materials are powerful 
enough to lure insects over considerable distances. Attractants of many kinds are 
being studied, but those consisting of natural chemicals produced by host plants or 
the insects themselves are receiving the most attention. 
Many important forest insects in the orders Lepidoptera, Coleoptera, and 
Hymenoptera produce sex attractants. They may be emitted directly from the 
insect, or they may emanate from the frass or excrement left from insects feeding 
under the bark (/0S2). The material emitted by certain species 1s enormously 
attractive. One female of the introduced pine sawfly attracted more than 11,000 
males (239). 
Sex attractants have long been used to some extent in surveys of a few forest 
insects, particularly the gypsy moth (225). For many years the tips of abdomens of 
virgin female moths were placed in specially designed traps to capture male moths. 
Research to improve on this technique led to the isolation and synthesis of the 
attractant material (634), and the subsequent synthesis of a closely related, com- 
paratively inexpensive, highly attractive material called disparlure (/06). Synthetic 
attractants are now used widely for detecting and evaluating gypsy moth as well as 
other forest insects, such as Douglas-fir tussock moth, Nantucket pine tip moth, 
17 
