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Ask Your PCA: How can farmers protect strawberry transplants?

Issue Date: Nov 11 2020
Edgar Godoy, CCA-WR/PCA, BioWorks, Central and Northern California

Crown and root rot is responsible for sporadic but serious plant losses during early establishment in California strawberry fields.

Many growers spend additional resources to buy more transplants and replant the areas that have a significant number of dead plants. Very often, the nurseries are blamed for the infection.

Crown and root rot in strawberry transplants may be caused by Phytophthora cactorum, P. citricola, P. megasperma, sans P. parasitica. It is also attributed to Colletotrichum acutatum. A lab diagnosis is needed to determine which pathogen caused the disease.

Growers may hedge their bets, so to speak, and buy transplants from several nurseries—usually two to three different nurseries—to reduce the risk of a potential disease infection. One nursery might have a problem, but another won't.

After transplanting, die-out may occur within a few weeks and necessitate replanting. Replanting is expensive. Growers may have to purchase more transplants, plus additional labor costs.

Strawberry transplants might die for other reasons. If crowns are not exposed after the soil is closed around the transplants, or if placement of the transplant is too shallow or too deep, plants die or grow poorly. Roots should be placed vertically in the planting slot and not be allowed to form a "J" shape. If this becomes an issue and there are active soil pathogens, plants might die within a few weeks after transplanting, and replanting will be needed.

Preplant soil fumigation and some systemic fungicides have helped minimize the losses, but the pathogen's ability to survive in the soil and its fast reproduction require other treatment options.

Biofungicides added to conventional preplant dip treatments offer safe, compatible and cost-effective root disease control. Biofungicides have unique and complex modes of action different from chemicals, which makes them excellent resistance-management tools. Reapplication is recommended four weeks later through drip irrigation.

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