Managing Soil Borne Diseases of Raspberry in Western States: Development of Decision Making Tools and Sustainable Management Systems
Horticultural Crops Research
2013 Annual Report
1a.Objectives (from AD-416):
1. Development of decision-making tools.
2. Develop sustainable management systems.
1b.Approach (from AD-416):
Through a combination of laboratory and field experiments we will develop decision-making tools and sustainable management systems for the control of Phytopthora spp. and plant-parasitic nematodes in raspberry production systems. Specifically we will use molecular techniques to characterize and determine virulence of Phytophthora spp. in raspberry. We will establish field trails in nematode-infested fields to identify raspberry plants resistant or tolerant to Pratylenchus penetrans. We will also begin to develop sustainable pest management systems for raspberry by establishing field trials in northern Washington that evaluate alternative was to broadcast fumigation to manage soil borne pathogens prior to establish a raspberry crop.
United States raspberry (Rubus idaeus) production is heavily concentrated in the Pacific Coast states, with over 90% of total fresh market production coming from California, and over 90% of total processing production grown in Washington. The soil borne pathogen Phytophthora rubi and the plant-parasitic nematode Pratlylenchus penetrans are both important, difficult to manage pests in these production systems. The goal of this multi-state, collaborative research is to develop tools for raspberry growers to better manage these organisms; this is the 3rd year of a 5 year project. For objective 1, characterize the virulence and population dynamics of Phytophthora species, approximately 200 plant samples were collected from Washington, Oregon, and California and Phytophthora species were isolated from this material. It was discovered that all but one of the raspberry plants was infected with P. rubi indicating that P. rubi is the only Phytophthora species responsible for root rot of raspberry in the Pacific Coast states. The pathogenicity and fungicide resistance of some of these populations of P. rubi are now being determined. For objective 2, identify sources of plant resistance to P. penetrans, a field trial was conducted in Washington to evaluate the response of eight raspberry varieties, as well as two Rubus species closely related to raspberry, to P. penetrans. The impact of P. penetrans on the establishment of the raspberry varieties was rapid, with an approximately 50% reduction in plant establishment 6 months after planting, regardless of variety. The closely related Rubus species were also host for P. penetrans and suffered from a reduction in establishment during the same time period. Finally, for objective 3, evaluate novel preplant management practices to control these organisms and permit successful raspberry establishment, a field trial comparing broadcast fumigation (the industry standard) to bed fumigation, alone and combined with cover crops was established. Initially, both bed and broadcast fumigation protected plants from P. penetrans compared to a nontreated control. During the two years post treatment, bed fumigation performed as well as broadcast fumigation. This research will continue for two more years and will provide Pacific Coast raspberry growers with information to better manage these production limiting pests.