Specific and early monitoring and evaluation of Lygus egg parasitization by Anaphes iole Girault has become a reality. We developed a molecular approach to detect the presence of this minute wasp developing within Lygus lineolaris (Palisot de Beauvois) and L. hesperus Knight eggs. Early and specific detection was achieved by amplification of parasitoid DNA fragment even at a trace level within its host. One pair of primers were designed based on cloned ribosomal DNA sequences of A. iole. These primers specifically flanked to wasp genomic DNA and generated a unique 661-bp band visualized on an agarose gel after polymerase chain reaction (PCR) amplification. This 661-bp DNA fragment was amplified only from those samples containing wasp DNA. With this technology, parasitism could be detected at a trace DNA level as low as 1 pg of genomic DNA (equivalent of 10^-6 total DNA from a adult wasp), and could be detected as early as the egg stage (less than 24 h after oviposition).