Effect of bean sprout residue on the hatching and density of the soybean cyst nematode Heterodera glycines in soil

The effects of the application of bean sprout residue to soil on the soybean cyst nematode (SCN) Heterodera glycines were evaluated in pot experiments. When bean sprout residue was applied into a soil infested with SCN at a rate of 1%, the number of SCN second-stage juveniles (J2), measured with the Baermann method, increased after 14 days of application and then decreased markedly after 35 days, indicating that some J2 hatched in response to a stimulant in the bean sprout residue and then starved to death in the absence of a host. Next, bean sprout residue was applied two or four times and the number of SCN after 7 weeks was estimated with real-time PCR, which enables quantification of all the forms of SCN (eggs, J2, cysts). Results showed that the SCN density did not change in the untreated control, while it decreased by more than 70% in the residue treatment. Such a hatching-stimulatory and subsequent eradication effect was observed in the water extract of bean sprout residue. Among different parts of bean sprout, both of the stem and root parts had a higher stimulatory effect for hatching, while a stimulatory effect decreased in the stem part greened by culturing under light conditions. These results revealed that bean sprout residue might function as an environmental-friendly control measure for SCN.