Reproductive controls serve as another form of biological control. The most widely known example involves the use of sterile males. Sterile males furnish an effective control against several insect pests. How does this work?
Males are raised in captivity and sterilized by irradiation or chemicals. The sterilized males are then released into the orchard or field in large numbers. The sterile males then "mate" with unsuspecting females, and since most insects mate only once, no offspring are produced by that female.
I bet you can think of one danger in this approach? What if the males aren't really sterilized? Release of large numbers of allegedly sterile males did occur in CA in attempts to control the Mediterranean fruit fly -- obviously counterproductive!
Another problem with some versions of this technique is that it produces equal numbers of sterile males and sterile females; that is, insects in general are sterilized and then released without regard to sex. The sterile females then dilute the effect of the sterile males, because some of them mate with the sterile males. These sterile females also damage the fruits when they oviposit (which they attempt to do even though they are sterile), opening an infection court for bacteria and fungi.
However, some laboratories have now produced genetically transformed sterile males. This genetic transformation means that genes encoding sterility will persist and be passed on from generation to generation. Other laboratories have also used classical genetics to produce lines that produce only males under factory conditions, avoiding the problem of "dilution" with sterile females.
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This page is maintained by Patricia Muir at Oregon State University. Page last updated October 26, 2002.