Detection of Hirsutella spp. and Pasteuria sp. parasitizing second-stage juveniles of Heterodera glycines in soybean fields in China

Soybean cyst nematode, Heterodera glycines, is widely distributed in soybean-producing areas, and causes great yield loss in China. The second-stage juvenile (J2) is the infective stage of the nematode; therefore reducing their numbers is important in managing this nematode. In a survey of fungal and bacterial pathogens of J2, 146 rhizosphere soil samples were taken from soybean fields distributed in 11 provinces and Beijing in China during May-August 1999. J2s native in soil plus those that remained after a 2 week incubation of soil with addition of 3000 J2s were extracted and examined for fungal and bacterial infection. Hirsutella minnesotensis was detected in 20.5% of the soil samples, Hirsutella rhossiliensis in 1.4%, and Pasteuria sp. in 26.0%. Hirsutella spp. were mainly detected in the relatively low pH soils containing more organic matter from Heilongjiang province (19.2%), whereas Pasteuria sp. was found in high pH soils with less organic matter from Anhui (10.2%), Henan (6.8%), Jiangsu (3.4%), and Shandong (2.7%). More Pasteuria sp. was detected in soils after addition of baiting nematode; detection methods had no difference in Hirsutella spp.