A new walnut block featuring two research trials were planted April 11, 2016 at the Lindcove Research and Extension Center (LREC) at Exeter, Calif., according to Elizabeth Fichtner, University of California Cooperative Extension farm advisor, Tulare County.

Fichtner established a rootstock observation trial and a study to screen biological and biorational compounds to help protect walnut rootstocks from soilborne pathogens. 

“Due to local disease pressure from thousand cankers disease, soil infestation with Phytophthora parasitica, and heightened local incidence of lethal paradox canker, LREC is the ideal location to challenge new rootstock genotypes generated by the walnut improvement program at UC Davis,” said Fichtner. 

The new observation block contains four experimental rootstocks and four commercial rootstocks including VX211, Vlach, RX1, and seedling Paradox. The rootstocks were June budded to the Chandler variety.

The Tulare block is one of six walnut rootstock trials established in California. The project is supported by a Specialty Crops Research Initiative grant and by the Walnut Board of California.

In a separate trial, Fichtner says commercially-available products sold for tree protection from soilborne fungi will be tested on seedling Paradox rootstock.

The root treatments include: endomycorrhizal fungi (MycoApply EndoMAXX, Valent); a bacterial biocontrol agent (Activate, Natural Resources Group); and a botanical extract mixture containing salicylic acid, a known compound involved in induced resistance (Root Rx, Redox Chemical).

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