Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2005
Publication Date: 6/1/2006
Citation: Li, J., Yan, F., Coudron, T.A., Pan, W., Zhang, X., Liu, X., Zhang, Q. 2006. Field release of mass-reared parasitoid Microplitis mediator (Hymenoptera: braconidae) for control of Helicoverpa armigera (Lepidoptera: noctuidae) in cotton fields in northwestern China’s Xinjiang province. Environmental Entomology. 35(3):694:699.
Interpretive Summary: The cotton bollworm is one of the most destructive pests of economically important field crops throughout the world. Insecticide applications to control this pest cost millions of dollars per year and have resulted in resistance to nearly all types of chemical control, increasing the importance of developing a biological component to control this pest. A beneficial wasp has been shown to be an efficient biological control agent for the control of the bollworm. Several combinations of frequency, site, and number of wasps released were tested to determine a procedure that provided the maximum control of the bollworm in cotton fields in China. Significant levels of parasitism were obtained which resulted in decreased plant damage, and suppressed bollworm populations that were lowered to below the level that causes an economic loss to cotton production. These results confirm that the wasp can be used to effectively control populations of the cotton bollworm in cotton fields. This information is valuable to researchers, agricultural companies, beneficial insectaries and producers; all of whom are searching for more effective methods to control the cotton bollworm.
Technical Abstract: Field experiments and surveys were conducted in 2003 and 2004 to evaluate the efficiency of using the parasitoid Microplitis mediator (Haliday) to control populations of cotton bollworm, Helicoverpa armigera (Hübner), in cotton fields in Northwestern China’s Xinjiang Province. Initial population levels of the second generation H. armigera in Southern Xinjiang were ca. 20-60% above the economic threshold of this pest (Guo,Y. Y. 1985; Zhang, Q.W. et al., 1988;Li, H. B. 1997). The longevity of field released female and male parasitoids was 7.64±0.36d and 3.88±0.35d, respectively. Field tests showed that the number of parasitized H. armigera increased with an increasing number of M. mediator cocoons released in the field. The release of 2,250 or 15,000 laboratory-reared M. mediator cocoons per ha in cotton fields resulted in a 38% and 61% parasitism of H. armigera in 2003, and 35% to 66% parasitism in 2004, respectively. The efficiency of the parasitoids varied considerably with different host populations and with the frequency and sites of release. Large-area releases of M. mediator in cotton fields of Shufu, Shule and Shache counties resulted in more than 60% parasitism and an 80% decrease in cotton boll and bud damage. The above results indicated that field release of M. mediator could be used effectively in managing cotton bollworm in cotton in Xinjiang.