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Parasitoid (Bracon cephi) effects on grain yield of selected genotypes of wheat infested by Cephus cinctus.

Wu, X., Cárcamo, H.A., Beres, B.L., and Pang, B. (2011). "Parasitoid (Bracon cephi) effects on grain yield of selected genotypes of wheat infested by Cephus cinctus.", Australian Journal of Crop Science, 5(9), pp. 1102-1107.


The wheat stem sawfly has been a major pest of spring wheat in the southern prairies of Canada and the adjoining parts of the United States for several decades. Bracon cephi (Gahan) is an important endemic ectoparasitoid of the wheat stem sawfly that can reach very high levels of parasitism. The objectives of this study were to determine the effect of B. cephi on the feeding damage (stem mining) caused by the sawfly and consequences on plant fitness in terms of grain yield in various hollow- and solid-stemmed wheat genotypes. This study was conducted at Coalhurst, west of Lethbridge, Alberta in 2003-2005, and 2008. Uninfested stems had lighter grain heads than those infested by the sawfly. There was no consistent difference in grain head weights between uninfested stems, sawfly infested (but dead), and those parasitized by B. cephi. In 2008, the length of the feeding tunnel was significantly shorter in parasitized stems than those cut or with dead sawfly larvae; in other years the difference between stems with dead larva and those parasitized by B. cephi were not significant. We conclude that although B. cephi reduced stem mining by the wheat stem sawfly it did not affect the stem seed weight. Nevertheless, reduction in stem lodging during the growing season and lower sawfly populations in following years are important reasons to conserve this parasitoid.

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