Revolutionary Product Now Available to Prevent Disease in California Leafy Vegetables

Posted 17 August 2001. Plant Health Progress.

(Greensboro, NC, July 30, 2001) Blockade™, The Plant Activator™, a revolutionary product that bridges the gap between genetic resistance and conventional disease control, has been registered by the California Department of Pesticide Regulation (CDPR) to prevent downy mildew in head lettuce, romaine lettuce and spinach, and white rust in spinach. Blockade is a breakthrough in disease prevention that will help protect quality and maintain high marketability of crops, according to Syngenta technical manager Dr. Allison Tally. 

In numerous public and private trials, lettuce and spinach have been protected from these devastating oomycete diseases. Blockade has no direct effect on pathogens. Instead, the unique new product works systemically to “activate” the plant’s own natural defensive genes to protect against tough bacterial and fungal plant diseases, Tally explains. “Blockade translocates through the plant for longer, more uniform protection than is normally achieved with fungicides that act as protectants,” Tally says. 

Acibenzolar-S-methyl, the active ingredient in Blockade, is the only product available with a unique action that mimics the natural Systemic Activated Resistance (SAR) response found in nature. In most plants, low levels of a pathogen inoculum naturally trigger a resistance response – much like the human body’s immune system mobilizes to fight a disease. In this way, Blockade works like a vaccination for the plant. 

After application, plants “activated” with Blockade release proteins that inhibit the growth of the advancing pathogen at several different sites, impairing disease development. The product’s unique mode of action minimizes the risk of resistance and makes Blockade ideal for IPM programs. Blockade features low use rates of just 0.75 to 1.0 ounce of product per acre for each application. Foliar applications of Blockade should be targeted early in the season. Prevention of downy mildew requires up to four early, preventive applications at seven- to ten-day intervals on head lettuce and up to two applications on romaine lettuce. For prevention of downy mildew and white rust of spinach, apply no more than three 0.75-ounce applications at seven- to ten-day intervals. 

Syngenta recommends using Blockade in an overall disease management plan that includes sound cultural and sanitation practices as well as use of traditional fungicides, especially if disease is present at the initial application. Workers may reenter fields just 12 hours after application. Blockade may be applied seven days prior to harvest in head lettuce, romaine lettuce and spinach.