Early Prevention Key to Lettuce Drop Control

Lettuce drop pathogens can live in the soil for several years.

More than 90 percent of the $2 billion U.S. lettuce crop comes from California and Arizona. With California responsible for approximately 75 percent of that production, growers can’t afford to gamble on disease wiping out their crops.

One especially destructive disease is lettuce drop (Sclerotinia minor and Sclerotinia sclerotiorum), which attacks the lettuce plant’s crown tissue and makes the plant unharvestable. Lettuce drop pathogens can live in the soil for several years with wet soil conditions most favorable for lettuce drop development.

Staying Ahead of Disease

At Rancho Guadalupe, LLC, in Santa Maria, California, lettuce production accounts for about 25 percent of the farm’s plantings. The 4,000-acre farm grows mostly head lettuce on conventional beds. Lettuce transplants are used from January through March, followed by seeding.

Disease protection plays a critical role in the Rancho Guadalupe production program, especially lettuce drop prevention. Depending on the year’s conditions, yield loss to lettuce drop can be 5 percent or greater.

“We treat all of our early and late lettuce with fungicide for lettuce drop prevention,” says Ruben Avila, pest control advisor, Rancho Guadalupe. “Transplant lettuce is sprayed approximately one month after planting and seed lettuce is sprayed after thinning. As days in the ground decrease, the application is made closer to the planting/seeding date. During the main season, we treat fields with a history of lettuce drop. To lessen disease pressure, we try to rotate crops, keeping the lettuce crop to a single planting per plot and not planting lettuce crops consecutively.”

Flexible Protection

In 2013, Avila tested DuPont Fontelis® fungicide on half of Rancho Guadalupe’s lettuce acres for lettuce drop protection.

“Fontelis® did a good job of controlling lettuce drop,” Avila says. “Even when spraying was delayed and plants had grown a little bigger than the ideal treatment stage, I was surprised at how well Fontelis® protected against disease.

“Fungicide application timing is important when treating for lettuce drop. You need to treat plants at the right stage to get maximum coverage on the crown for adequate protection,” Avila notes.

Fast, Long-Lasting Control

Fontelis® delivers preventive and curative protection against foliar diseases in vegetables, fruits, almonds, hazelnuts (filberts) and pistachios. Along with fast-acting and long-lasting broad-spectrum disease control, Fontelis® offers excellent crop safety. It works well under light and heavy disease pressure, and fits easily into many crop management programs. Featuring a single active ingredient, it is ideally suited for resistance management plans.

In addition to lettuce drop, Fontelis® delivers reliable control of a variety of diseases, including Alternaria leaf blight, powdery mildew, brown rot, gray mold and leaf spot.

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