Can the northern root-knot nematode, Meloidogyne hapla, be controlled by the fungus Clonostachys rosea? : an experimental study

Abstract: The northern root-knot nematode, Meloidogyne hapla, is causing great economical losses to growers worldwide. There is a need for alternative control measures that are environmentally sustainable and effective against the nematode. Biological control is one promising control measure and there are multiple biological control agents on the market against fungal pathogens and insects. One such biocontrol agent is the fungus Clonostachys rosea. In this experiment the biocontrol effect of C. rosea against the root-knot nematode M. hapla was evaluated. The investigation included an antibiosis in vitro experiment and a pot experiment with carrot and lettuce under controlled conditions. Additionally, the effect from drought on M. hapla infection and C. rosea biocontrol was tested. Drought increased the infection by M. hapla on carrot and caused a significant (P < 0,001) decrease in fresh and dry root weight and shoot dry weight, indicating a higher parasitic effect on plant mass of infected plants during dryer periods in cultivated fields of carrot. No biological control effect from C. rosea on M. hapla was detected, nor any growth promoting effects from the fungus on the plants. However, plants treated with C. rosea showed an increased tolerance towards drought stress by not showing significant distinction between plant mass under normal and drought conditions, which was seen in the other treatments. Though, an error due to a high buildup of roots in the peat soil made it difficult to count the galls on plant roots, affecting the result of biocontrol effect and actual nematode infection. The use of sand might have simplified the rinse of the roots and a more accurate result could have been obtained.