Fauna Of Entomopathogenic Nematodes And Biology Of Its Fine Strains In Gansu Province

As more attention of Entomopathogenic nematodes (EPN) has been paid in the biological control of insect pests, the resources of EPN with strong infection potential and fine quality were accelerated seeking. The fine local nematodes plays important roles in the application of biological control to find out the distribution of EPN in Gansu province and grasp the biological characteristics of nematodes.EPN, which were extracted with Galleria mellonella trap method, were recovered from 6 out of 13 regions sampled, with 29 positive sites (7.6%) out of 382 sites sampled in Gansu province of China during 2006 and 2007, mainly occurring in the center and east areas of Gansu Province.Eight species of EPN were identified according to the morphology: five species in Steinernema were respectively Steinernema feltiae,S. bicornutum,S. affin,S. krusse and S. karil; three species in Heterorhabditis were respectively Heterorhabditis brevicaudis,H. megidi and H. marelatu. Four species were new records in China: S. affin,S. krusse,S. karil and H. marelatu. A single nematode isolate was recovered at each of the positive sites, of which 26 (89.7%) were steinernematid isolates and 3 (10.3%) were heterorhabditid isolates. EPN resources were relatively rich for the arid climate in Gansu Province.Research showed that the recovery rates in sandy loam, loam and clay soils were 12.2%, 8.8% and 5.3% respectively. The recovery rates in loam, sandy loam and clay soils were respectively 51.7%,37.9% and 10.4% with soil samples of all EPN. That explained sandy loam and loam were fit for the occurrence of EPN.The investigation showed that the incidence rates in the soils of orchards, cereal fields, vegetable gardens and non-cultivated lands were 10.4%, 9.2%, 5.2% and 3.3% respectively. The recovery rates of EPN in cultivated lands and non-cultivated lands were respectively 93.1% and 6.9% with soil samples of all EPN.The biological characteristics of three fine quality strains (0627M strain of H. megidis, 0619HT strain of S. feitiae and 0657L strain of S. krussei) were studied. The results showed that in vivo of the same quality Galleria mellonella larvae, nematode reproduction of 0627M strain was highest and its infection cycle was longest. The dosage of 0627M strain and the dosage of 0619HT strain infection used by the G. mellonella were small, and 0619HT strain had higher speed of infection under the same dosage. The optimum temperature scope of infection activity belonging to 0627M strain, 0619HT strain, 0657L strain was 20℃~25℃, 15℃~30℃, 20℃~30℃respectively. When the moisture content of sandy soil is below 1.0%, three EPN lose their infection activity at 25℃. The study demonstrates that three nematodes species have a significant practical potential in preventing and controlling the field harmful insects.