IPM and Biological Control of Meloidogyne chitwoodi and the Colorado Potato Beetle
Introduction – Description of the Problem:
There are two pests of potato, Solanum tuberosum, in the pacific Northwest, the Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) and Meloidogyne chitwoodi Golden et al., commonly called the Columbia root knot nematode (RKN) that are of economic importance in Washington State potato production. Above ground, the CPB can completely defoliate potato plants in 1-2 generations (Hare et al, 1980), with most extensive damage caused by the larval stages of the beetle. Due to the risk of crop loss conventional potato growers rely on “calendar sprays” of broad-spectrum pesticides as frequently as every 10 days for CPB control, making potatoes amongst the most intensively sprayed crops in the region. Below ground, potato tubers are attacked by the plant parasitic nematode RKN, a prevalent problem for Washington state potato growers; this nematode species can have at least 5 generations within one growing season. The use of insecticides against CPB and fumigants against RKN deplete above ground and below ground diversity, as well as increase the risks of toxic runoff into groundwater. Luckily, the lifecycle of CPB involves an underground stage which is found in the same soil habitat as RKN, i.e. near the potato rhizosphere during the growing season, making them ideal targets for using one or two biological control methods to simultaneously target both two pests. Mustard seed meal and entomopathogenic nematodes (EPN) have shown biocontrol potential against both the nematode and the beetle on potato.
The purpose of this experiment is to find out if mustard seed meal and/or entomopathogenic nematodes will control both the root knot nematode and the beetle and protect the potato tubers.
The following 2 x 3 multifactorial experiments were used to test our hypotheses:
1) determine whether mustard seed meal of Brassica carinata can decrease root knot nematode populations;
2) determine whether mustard meal amendment has a negative effect on EPN infectivity of CPB, and EPN suppression of root knot nematode; and
3) determine if the two species of EPN, S. feltiae or S. riobrave can infect the 4th instar CPB larvae and cause mortality.
The field data from 2006 yielded successful results, as did the greenhouse trials (3x). Initially, there was difficulty obtaining mustard meal, as the initial source reneged on the offer of giving us mustard meal and we had to get another type of mustard meal in less than a month for the field season. But we found a source from Italy that was happy to oblige.
Impacts and Contributions/Outcomes
This research has generated a lot of interest in the use of EPN in research, and the use of mustard meal with farmers.