Category Archives: Fungicides

Crop Breeding Failure Led to Increase in Fungicides in CA Spinach Fields

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The breeding of crop varieties that are resistant to pest organisms is often touted as an effective means of replacing pesticide use. And yet, pest organisms mutate and overcome the plant’s resistance. According to the California Department of Pesticide Regulation, fungicide use in California spinach fields has doubled in the last decade. The reason for the increase has been the breakdown of the plant’s resistance to mildew (Peronospora farinosa f. sp. spinaciae).

“Downy mildew disease is the most important disease problem facing the extensive spinach industry in California. … While downy mildew has been around California spinach fields for decades, the last few years have seen the development of four or five new races. Each new race potentially overcomes the resistance factors in the cultivars being planted at that time, leaving the crop susceptible to severe damage.”

“Integrated management steps must be used. … Resistant cultivars will remain a foundational piece of such a program. Judicious use of effective fungicides will remain important.”

Authors: Steven Koike and Jim Correll
Affiliation: University of California and University of Arkansas, respectively
Title: Spinach Downy Mildew: Outlining the Challenges.
Publication: Crop Notes (University of California Cooperative Extension)

Inability to Control Pest Damage Limits U.S. Organic Hop Acreage

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Hops damaged by mites, aphids and mildew are of poor quality and are unacceptable for brewing beer. Only 2% of U.S. hop acres are organic because without the use of synthetic chemical insecticides and fungicides, organic hop growers are extremely vulnerable to having their crop rejected by brewers due to poor quality. This situation is described in the following recent article…

“Demand for organically grown hops from consumers via the brewing industry is on the rise; however, due to high [nitrogen] requirements and severe disease, weed, and arthropod pressures, hops are an extremely difficult crop to grow organically.”

“Disease, fungal infection, and arthropod pests that can damage hop cone quality are controlled by frequent and persistent application of pesticides in conventional hopyards, an option unavailable to organic hop growers. … Due to the direct correlation between quality and price of hops, a crop can be drastically affected by pests and diseases that alter not just the brewing quality but also the aesthetics of the crop as well. Any loss of quality can cause a crop to lose value or be damaged to the point at which it is completely unsalable.”

“The organically certified chemical controls against arthropod pests in organic crop production are limited and generally less stable and effective than their synthetic counterparts due to uncertain efficacy, potential harm to beneficial arthropods, and cost.”

Authors: Samuel F. Turner, et al.
Affiliation: Washington State University Department of Crop and Soil Sciences
Title: Challenges and opportunities for organic hop production in the United States.
Publication: Agronomy Journal. 2011. 3(6):1645-54.