How Does Sunn Hemp Suppress Plant-parasitic Nematodes?
Sunn hemp uses different modes of action to suppress plant parasitic nematodes, making it an efficient cover crop for nematode management. Sunn hemp is not only a poor host or nonhost to many plant-parasitic nematodes (Table 1), but it has been shown to produce allelopathic (toxic) compounds against several key nematode pests. Jasy and Koshy (1994) demonstrated that leaf extract of sunn hemp was lethal to burrowing nematode (Radopholus similis) at dilutions of 1:5 within 24 hours. Wang et al. (2001) also found that sunn hemp leaf leachate essentially stopped movement of the reniform nematode, R. reniformis. Sunn hemp also can enhance natural enemies of plant-parasitic nematodes, such as fungi that trap nematodes or feed on their eggs (Wang et al., 2001). Besides suppressing plant-parasitic nematodes directly, sunn hemp can also manage nematode damage on crop indirectly by increasing plant tolerance against these pests. Sunn hemp amendments have been demonstrated to enhance free-living
