- Fruits: berries (other)
- Pest Management: integrated pest management, prevention, soil solarization
- Production Systems: general crop production
The Pacific Northwest of the U.S. encompasses 90% of processed raspberry acreage nationwide. The duration of harvestable plantings has declined from >10 years to approximately 5 years. Root rot damage by Phytophthora rubi (Pr) and Pratylenchus penetrans has been associated with this decline, but soil characteristics that promote these pathogens are not well understood. Currently, broadcast pre-plant fumigation is used to manage soil-borne pathogens; a practice that is expensive and chemically intensive. This research aims to develop a quantitative molecular assay for Pr in raspberry soil and roots and investigate alternatives to fumigation for pre-plant management of these pathogens.
In the Pacific Northwest, commercial raspberry growers have several pathogens and plant-parasitic nematodes that can cause yield decline over time (McElroy, 1992). New restrictions on whole-field fumigation and on many common fumigant products (USEPA, 2009) will require growers to implement novel approaches to manage soil-borne pathogens and plant-parasitic nematodes that are less reliant on chemical treatments. Biologically-based approaches for managing pathogens have been used in other perennial crop production systems (Mazzola et al., 2010; Bailey and Lazarovits, 2003; Zasada et al., 2003), but these require further investigation to be effectively implemented into raspberry production systems.
Integrated control of pests in raspberry production systems has been investigated (Pinkerton et al., 2009; Pinkerton et al., 2002; Maloney et al., 2005; Wilcox et al., 1999). Integrated management requires an input of organic matter into the soil, addition of a biocontrol agent or bio-pesticide, or manipulation of the soil ecosystem to encourage beneficial organisms and minimize pest activity and survival. One such component of this type of system is biofumigation.
Biofumigation has been defined as the suppressive effect of brassicaceous materials on soil-borne pests in part due to the release of toxic isothiocyanates (ITC) and other compounds, byproducts of glucosinolate hydrolysis (Motisi et al., 2010). Release of these compounds is mediated by several factors, including particle size, soil temperature and water availability. The composition of ITCs will vary by species (Fahey et al., 2001), thus influencing how this material influences plant health and affects soil biota. Historically, brassicaceous plant materials have been incorporated into soil as green manures for pathogen control and nitrogen supplementation, however the use of brassicaceous seed meals is also of interest (Mazzola and Brown, 2010; Snyder et al., 2009; Zasada et al., 2009). Seed meals are a byproduct of the biofuel industry oil extraction process and may increase in volume and availability in the Pacific Northwest in the future (Higgins, S, personal communication).
Solarization is another fumigant alternative method that has been used in annual and perennial cropping systems (Stapleton, 2000). This approach uses passive solar heating of moist soil mulched with plastic sheeting. In Washington, the use of solarization did control common raspberry pathogens in the field (Pinkerton et al., 2009; Pinkerton et al., 2002), but results were not consistent across years due to the variability of the mild, marine climate in this region. Exposure time required to kill P. rubi was estimated to be 222 hours at 29o C, and all locations in this study exceeded the desired heat units (Pinkerton et al. 2009). Solarization in combination with organic amendments has also been investigated (Gigot et al., 2010 (APPENDIX A); Klein et al., 2007; Gelsomino et al., 2006) and may be a viable choice for raspberry growers as opposed to solarization alone, but further research is needed. Tarping of brassicaceous plants increased the efficacy of this material alone in coastal areas of California (Zasada et al. 2003)
Application of biofumigants will require more information on how the biofumigant affects target and non-target organisms, as well as how these products influence crop performance and the long-term suppression of pathogens. This study investigates the effects of brassicaceous seed meals in combination with soil solarization on two raspberry pathogens, Phytophthora rubi and Pratylenchus penetrans, in field and greenhouse trials. In addition, we address some of the issues associated with application of this material, including application rate, host plant toxicity and impact on non-target organisms, such as beneficial nematode communities.
1. Develop a real-time PCR assay and complimentary bait assay for quantifying P. rubi inoculum in raspberry roots and field soil
2. Measure P. rubi and plant pathogenic nematode survival and infectivity in alternative bed management treatments
3. Assess common soil quality indicators in alternative bed management treatments (nematode community, particulate organic matter, water stable aggregates, water infiltration, pH, nutrient status)