WSU Whatcom County Extension

Raspberry Soil Fumigation

WSU Whatcom County Extension        

Truck in Field

 

Raspberry Soil Fumigation

 

The two most important soilborne pathogens affecting raspberry production in northwestern Washington are the oomycete Phytophthora rubi and the plant-parasitic nematode Pratylenchus penetrans. Left untreated, both organisms can cause decreased productivity and increased mortality of red raspberry plants over the life of the planting.

Phytophthora rubi is a water mold that causes Phytophthora root rot of raspberry. Above-ground symptoms include scorched or bronzed leaves that eventually wilt and die. Fruit stems are usually shortened and berries, if formed, remain small and wither before ripening. Infected plants may form some new roots and appear to recover, but the new roots are often weak and lack lateral development. The new roots subsequently become infected during cold, wet weather in fall and winter so that the plant progressively declines and becomes unproductive.  In a recent survey, P. rubi was detected in 100% of surveyed fields.

The plant-parasitic nematode, Pratylenchus penetrans, is also a major pest of red raspberry, reducing yield and cane growth, and leading to economic losses. Pratylenchus penetrans is a migratory endoparasite, migrating between the soil and roots. On raspberry, P. penetrans feeding on feeder roots can reduce the capacity of the plant to take up nutrients and water. Pratylenchus penetrans was shown to cause 24% mortality of red raspberry plants after two years. The rate of raspberry decline depends upon the nematode population density but usually occurs over a 3- to 4-year period. Pratylenchus penetrans is prominent in western Washington where it has been shown to reduce raspberry vigor

Currently the majority of raspberry growers in Washington broadcast fumigate prior to planting to manage P. rubi,  P. penetrans and other soil borne pathogens. The most commonly used fumigants in this crop production system are Telone® C-17 and C-35 (81:17 and 64:35 1,3-dichloropropene:chlorpicrin, respectively). In 2010, the U.S. EPA issued new Reregistration Eligibility Decisions (RED) for the soil fumigants chloropicrin, metham sodium/potassium and dazomet which means that there will be future limitations imposed upon the use of Telone® C-17 and C-35 because they include chloropicrin. In December 2012 the final labels were issued for these soil fumigants.

Our long-term goal is to develop IPM tactics for raspberry growers to better manage soil borne pathogens and plant-parasitic nematodes by developing and promoting the adoption of sustainable management systems for P. rubi and P. penetrans, two of the most important pest problems for raspberries in the Pacific Northwest.
The objectives of this project are to:

  • Determine the re-colonization potential of P. penetrans and disease potential of P. rubi in broadcast vs. bed fumigated fields and quantify the impact of fumigation treatments and soil borne pathogenson red raspberry establishment
  • Promote implementation of fumigant alternatives, and grower understanding of EPA REDs through field days, grower meetings, web-based decision-making tools, and printed materials.

 

 

 

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu