Multifaceted biocontrol methods against the Columbia root knot nematode, Meloidogyne chitwoodi, and the Colorado Potato Beetle, Leptinotarsa decemlineata, pests of potatoes in Washington State

Mustard seed meal from Brassica carinata has shown both nematicidal as well as insect oviposition deterring properties against the root knot nematode Meloidogyne chitwoodi, and the Colorado Potato Beetle (CPB), Leptinotarsa decemlineata, respectively. In addition, entomopathogenic nematodes (EPN) have shown biocontrol potential against both CPB and M. chitwoodi. The objectives of this research were to 1) determine whether entomopathogenic nematodes can reduce M. chitwoodi populations, 2) determine whether entomopathogenic nematodes can infect CPB larvae, 3) determine whether mustard seed meal can decrease M. chitwoodi populations, 4) determine whether the two methods (mustard seed meal and EPN) can be used simultaneously against both the CPB and M. chitwoodi, and 5) determine if the addition of mustard seed meal amendment deters CPB oviposition. Field and greenhouse trials were conducted in WSU Prosser, WA and WSU Pullman, WA in 2006 and 2007. Mustard seed meal alone, EPN, and combination of mustard seed meal and EPN significantly reduced the percent culled potato tubers, percent infection, and infection index due to M. chitwoodi in field trials. In the greenhouse trials, mustard seed meal, S. feltiae and S. riobrave, and treatment combinations of mustard seed meal with species of EPN reduced M. chitwoodi infection significantly. Both species of EPN were able to infect CPB larvae in the field and greenhouse, regardless of mustard seed meal amendment. The oviposition rates of CPB in the field were reduced significantly on mustard seed meal amended plants compared to the untreated control. In the greenhouse there were no effects of mustard seed meal amendment on CPB plant choice. EPN and mustard seed meal have shown promising potential as biological control methods to control both the above ground herbivorous insect pest, CPB, and the below ground nematode pest of potato tubers, M. chitwoodi. This multifaceted approach will provide potato growers with new options for sustainable control of both the root knot nematode and the insect pest