Surprise! Your Strawberries are Moldy

Grey mold on strawberries

Gray mold on strawberries

Consumers sometimes buy picture-perfect strawberries only to find them covered in mold after a few days. The cause: the gray mold fungus which infects the berries in the field but which remains symptomless until the fruit ripens. The fungus produces a velvety gray growth on the surface of the berry. Gray mold spreads in shipping containers when the fungus grows from a rotting berry to an adjacent healthy fruit. 100% of US strawberry acres are estimated to be infected with the gray mold fungus. Widespread infections are prevented with fungicide treatments.

“Gray mold is one of the most economically important diseases of cultivated strawberry (Fragaria × ananassa), and a significant threat to the United States’ $2.4 billion strawberry crop… Crop losses resulting from gray mold disease are especially severe under moist weather conditions, and occur not only during the crop growing season but also after harvest and during storage and transit.

The control of gray mold in commercial strawberry fields is largely dependent on the application of fungicides during bloom and fruit maturation.”

Authors: Grabke, A., et al.
Affiliation: Clemson University.
Title: Fenhexamid resistance in Botrytis cinerea from strawberry fields in the Carolinas is associated with four target gene mutations.
Source: Plant Disease. 2013. 97[2]:271-276.

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Fungicides Enable China to Lead in Global Production of Vegetables

Greenhouses in China

Greenhouses in China

China produces nearly half of the world’s vegetables- five times the U.S. share. China’s increase in vegetable acreage between 2000 and 2004 (5.7 million acres) exceeded the entire vegetable acreage in the United States (3.7 million acres). China’s vegetable production has grown mainly to meet domestic demand from its 1.3 billion citizens. There are over 7.3 million acres of greenhouse crops in China and the growing conditions in the greenhouses are conducive to fungal outbreaks making fungicide use necessary.

“Gray mold caused by B. cinerea has become one of the most economically important diseases, since the rapid development of greenhouse cultivation in the 1990s in eastern China. B. cinerea severely reduces the yield and quality of greenhouse vegetables such as eggplant, tomato, cucumber and pepper. Jiangsu and Zhejiang provinces are the major vegetable production regions of eastern China, where unheated plastic greenhouses have been in use since 1998. Growers depend on regular fungicide treatments approximately every 7 days from November to May, besides some cultural practices such as ventilation to control the epidemic of B. cinerea.”

Authors: Zhang, C. Q., et al.
Affiliation: School of Agriculture and Food Science, Zhejiang Forest College, China.
Title: Evolution of resistance to different classes of fungicides in Botrytis cinerea from greenhouse vegetables in eastern China.
Source: Phytoparasitica. 2009. 37:351-359.

It Never Rains in Southern California, But When It Does, Fungicides are Essential

Gray Mold

Gray Mold

Most of the table grape production in the U.S. is located in the San Joaquin Valley. Rainfall at harvest is uncommon. However, when it does rain, gray mold can reach epidemic proportions if fungicides are not used. Gray mold is caused by a fungus that is activated by rainfall. The fungus produces a short tube with a suction cup and a peg that forces its way through the grape cuticle. Inside the grape, the fungus grows and exudes enzymes that degrade the fruit. Cracks form in the grapes and spores are produced that spread gray mold to other grape clusters. Even a single infected fruit within a table grape package can cause severe losses.

“Timing of fungicide applications to control gray mold is primarily driven in vineyard environments by the occurrence of rainfall. Rainfall at harvest, an uncommon event in the San Joaquin Valley of California, causes abundant production of inoculum and epiphytotics of the disease in vineyards, and fungicide applications are critically needed when this rare event occurs. This area, where most of the table grape production in the United States is located, is typically rainless throughout these periods and B. cinerea seldom causes significant vineyard bunch rot, but it routinely causes substantial postharvest decay if measures to control it are not taken.”

Authors: J.L. Smilanick, et al.
Affiliation: USDA ARS
Title: Control of postharvest gray mold of table grapes in the san Joaquin valley of California by fungicides applied during the growing season
Source: Plant Disease. 94[2]:250-257. 2010.

New Fungicide Revolutionizes the California Pomegranate Industry

Untreated vs. Treated

Untreated vs. Treated

In recent years, the California pomegranate industry has grown dramatically. Pomegranates have gained high visibility with the public through a number of health benefits due to some of the fruit’s constituents in preventing cancer. The crop’s recent success was not assured until a fungicide was registered to prevent mold from developing on the fruit in storage. In fact, before the introduction of the fungicide, the pomegranate industry in California was almost destroyed by the mold problem.

“Gray mold, caused by Botrytis cinerea, is a fungal disease that can be a serious threat to the pomegranate industry. In the 1999 and 2000 growing seasons, gray mold destroyed approximately 30% of California’s harvested pomegranates. California pomegranate packers had difficulties storing fruit for two to three weeks, let alone the goal of two to three months of storage that they needed to reach holiday markets from November to January around the world. Costs associated with repackaging, box losses, and price discounts, as well as crop rejections by retailers, almost destroyed California’s pomegranate industry.

In 2001, Scholar, a new postharvest fungicide containing the active ingredient fludioxonil, received a Section 18 emergency exemption registration for use on pomegranate in California. With this, a postharvest treatment was registered on this crop for the first time.

With these treatments, fruit losses due to gray mold were reduced substantially. Thus, in 2003, 5% of the harvested crop was lost as compared to the previous average of 30% lost in 1999 to 2002 when postharvest treatments were either not available (1999 and 2000) or were not widely  used because most packinghouses had not  installed treatment equipment (2001 and 2002). As a direct result, the crop yield (boxes per acre) in 2003 increased by 66.9% and the gross revenue increased by 61.8% as compared to the average yield and average revenue from 1999 to 2002, respectively.

Profitability to the California pomegranate industry was also regained through an extended storage life of the Scholar-treated fruit. Thus, fruit can now be stored for up to five months as compared to approximately one month before use of the fungicide. This now vastly extends the marketing potential of this fruit of passion.”

Authors: Eric C. Tedford (1), James E. Adaskaveg (2), and Alex J. Ott. (3).
Affiliations: (1) Syngenta Crop Protection. (2) Department of Plant Pathology, University of California. (3) California Grape and Tree Fruit League.
Title: Impact of Scholar (A New Post-harvest Fungicide) on the California Pomegranate Industry
Source: Plant Health Progress. February 16, 2005.