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Title: The impact of Cu, Zn and Cr salts on the relationship between insect and plant parasitic nematodes: a reduction in biocontrol efficacy

item SUN, YANG - Nankai University
item BAI, G - Nankai University
item WANG, Y - Nankai University
item ZHANG, YUAN-YUAN - Nankai University
item PAN, JIE - Tianjin Institute Of Agricultural Resources And Environmental Sciences
item CHENG, WEI-MIN - Agro-Environmental Protection Institute
item FENG, XIOLING - Nankai University
item LI, HUI - Tianjin Center For Quality Testing And Inspection Of Agricultural Products
item MA, CHENG-CANG - Tianjin Normal University
item RUAN, WEI-BIN - Nankai University
item Shapiro Ilan, David

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2016
Publication Date: 6/5/2016
Citation: Sun, Y., Bai, G., Wang, Y., Zhang, Y., Pan, J., Cheng, W., Feng, X., Li, H., Ma, C., Ruan, W., Shapiro-Ilan, D.I. 2016. The impact of Cu, Zn and Cr salts on the relationship between insect and plant parasitic nematodes: a reduction in biocontrol efficacy. Environmental Science and Technology. 107(11):108-115.

Interpretive Summary: The soil contains many beneficial organisms. One example of the “good guys” in the soil are beneficial nematodes (also called entomopathogenic nematodes); these small round worms that are used as environmentally friendly bio-insecticides and reside naturally in many soil ecosystems. These beneficial nematodes can also be used to suppress harmful plant parasitic nematodes that attack crop plants (thus, the good nematodes suppress the bad ones). Overuse of fertilizers in agriculture and greenhouse settings can cause a buildup of certain heavy metals, which may be toxic to various organisms. In this study we discovered that heavy metals that build up due to overuse of fertilizers are specifically detrimental to beneficial nematodes and impair their ability to control plant parasitic nematodes such as root knot nematodes.

Technical Abstract: The goal of the present study was to investigate the effects of excessive fertilizer application on the accumulation of potential toxic elements in greenhouse soil, and the direct effects on beneficial organisms (specifically, the insect parasitic nematodes known as entomopathogenic nematodes, EPN). The first study was a survey in vegetable greenhouses with various durations of intensive nutrient management (1, 2 and =5 years); intensively managed greenhouses were constructed in grain fields and contained natural soil floors; thus the greenhouse plots were also compared with (lesser managed) open grain fields, which were considered as a baseline. The second study was a series of assays that evaluated the direct impact of Cu, Zn and Cr on the function of EPN. In the field survey, we found that with increasing time of intensive soil total nitrogen, total phosphorous, Cu, Zn and Cr significantly and gradually increased, up to 159%, 339%, 169% , 197% and 102%, respectively. In the second study, the entomopathogenic nematodes, Steinernema carpocapsae (Sc), and Heterorhabditis bacteriophora (Hb) suppressed the penetration of plant parasitic nematodes (Meloidogyne incognita) into cucumber roots. However, pretreatment with heavy metal Cu, Zn or Cr impaired the suppression of M. incognita by Hb or Sc. Thus, we discovered that heavy metals exert more negative effects on EPN relative to plant parasitic nematodes. Also, these results indicated that heavy metal accumulation exerts detrimental effects on the top-down control of plant parasitic nematodes (i.e. suppression of a plant parasitic nematode by entomopathogenic nematodes).