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Title: A comparison of novel entomopathogenic nematode application methods for control of the chive gnat, Bradysia odoriphaga (Diptera: sciaridae)

Author
item BAI, GUANG-YING - Nankai University
item WANG, XIO-YING - Nankai University
item MA, HAI-KUN - Nankai University
item SHEN, GUANG-SHUANG - Nankai University
item FENG, XIOLING - Nankai University
item PAN, JIE - Tianjin Institute Of Agricultural Resources And Environmental Sciences
item GU, XI-SHU - Tianjin Institute Of Plant Protection
item RUAN, WEI-BIN - Nankai University
item Shapiro Ilan, David

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2016
Publication Date: 11/21/2016
Citation: Bai, G., Wang, X., Ma, H., Shen, G., Feng, X., Pan, J., Gu, X., Ruan, W., Shapiro Ilan, D.I. 2106. A comparison of novel entomopathogenic nematode application methods for control of the chive gnat, Bradysia odoriphaga (Diptera: sciaridae). Journal of Economic Entomology. 109(5):2006–2013.

Interpretive Summary: Beneficial insect-killing nematodes (also called entomopathogenic nematodes) are small round worms that are used as environmentally friendly bio-insecticides. In order to use the beneficial nematodes effectively we need to know the best nematode species to use and the best methods for applying them. In this study we tested the beneficial nematodes’ ability to control the chive gnat, which is very important insect pest of chive plants. We tested two different species of nematodes (called Heterorhabditis bacteriophora and Steinernema carpocapsae). We also tested different methods of applying the nematodes including application of the nematode species alone or in combination, and application of nematodes in water suspension versus in infected host cadavers. Application in infected host cadavers means applying the nematodes in dead insects that have reproducing nematodes inside. We discovered that the nematode species H. bacteriophora is better than S. carpocapsae for killing the chive gnat, and application of mixed nematode species does not offer any advantage. We also discovered that the cadaver application approach was superior to aqueous application. These findings will be useful in developing a safe and effective pest management strategy for the chive gnat, and will have applicability for use of beneficial nematodes in other cropping systems such as fruit and tree nut orchards.

Technical Abstract: Chive gnat, Bradysia odoriphaga, is the most serious pest of Chinese chive, and causes serious yield loss. Chemical pesticide application has become a necessary step each harvest and thus causing serious public health and environmental risks. We evaluated the efficacy of entomopathogenic nematodes (Heterorhabditis bacteriophora and Steinernema carpocapsae) against B. odoriphaga under Petri dish trial and pot trials. Additionally, we compared the effect of application type (cadaver vs aqueous) and a mixture of application types (cadaver vs aqueous) and entomopathogenic nematode species (Heterorhabditis bacteriophora vs Steinernema carpocapsae) on B. odoriphaga control. The results showed that B. odoriphaga mortality was significantly higher at 216 h after nematode inoculation under Perti dish trials, and the optimal density was 100 infective juvenile nematodes per insect larva. Results did not indicate superior efficiency when mixed species treatments were employed. The cadaver treatment showed higher mortality of B. odoriphaga and higher biomass of Chinese chive as compared to the aqueous treatment, and the H. bacteriophora treatment had better performance than S. carpocapsae. The combination of nematode species or application type did not cause any synergistic effects. Our findings indicate that entomopathogenic nematodes might be an ideal alternative biological agent in the integrated management of B. odoriphaga to produce high quality of Chinese chive.