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Disease & Weed Control

New technologies lead to efficient herbicides and fungicides
By Nancy Riggs


Controlling weeds and diseases in vegetable crops continues to be a major concern for growers. Dr. Tom Lanini, University of California, Davis, said, "While weed control is expensive, the crop value continues to warrant weed control."

While Lanini noted that some manufacturers are hesitant to develop herbicides for food products because of liability concerns, new technologies are producing new products. New products and expanded EPA labeling continue to offer growers increased options in controlling weeds and diseases in their crops.

Weeds can reduce yield and quality in several ways and can increase harvest costs.

"Some weeds are real hogs for nutrients and water," Lanini said. If crops have insufficient nutrients and water available, lower-quality crops will result. Weeds can shade crops, delaying ripening. Weeds impact harvesting efficiency by requiring extra time and labor costs, and weeds can jam mechanical harvesters in crops such as processing tomatoes. Both the cost and availability of labor is increasingly an issue for growers across the country. A number of states are intensively enforcing illegal immigrant laws, thereby increasing the labor shortage throughout the vegetable growing industry.

Development of herbicide-resistant weed species is a major concern.

"Growers have to spray repeatedly," said Dr. Peter Dittmar, University of Florida. "If one plant is missed, that plant will produce progeny that will be herbicide-resistant."

Dittmer noted that using the correct herbicide rate and monitoring fields are both essential to effective weed management. "If a weed isn't killed by the herbicide, it must be removed," Dittmar said.

Along with weed issues, most commercial growers manage crop diseases.

"Diseases are more prevalent in cool, wet settings, and most of the cool-season crops grown in late winter across Florida and south Texas are when rain increases," said Dr. Juan Anciso, extension specialist, Texas A & M University. Organic growing is gaining in the commercial growing industry, and California, largest producer of commercial vegetables, now is home to about 500,000 acres of organic production. Organic growing requires natural products to control weeds and diseases, opening up a new industry in development of those products.

Manufacturers continue to respond with increasingly cost-efficient products that contribute to effective weed and disease management. While new products are often decades or more in development from the early scientific findings stage to the issuance of EPA registration and state approvals, new herbicides and fungicides or new labeling continue to help growers assure profitable operations. Some of the new herbicides and fungicides, and products with recent label changes, are featured below.


Broccoli crop quality may be reduced by weeds.
PHOTO COURTESY OF DR. PETER DITTMAR.

Herbicides

Sharpen and Optil

Both Sharpen and Optil incorporate Kixor technology, which is a potent inhibitor of chlorophyll biosynthesis, resulting in a rapid buildup of reactive oxygen species and lipid peroxidation of the cellular membranes. This drives a rapid loss of membrane integrity. Both products are EPA-labeled for use on dry field peas, chickpeas, English peas and snap peas. Manufacturer's directions for use on vegetables indicate its use at differing rates on the different crops.

Dan Westburg, BASF technical marketing manager, cited the benefits of Sharpen in its ability to provide pre-planting through post-emergent weed control. "It is applied as a broadcast spray and can be used prior to planting through emergence," Westburg said.

Optil provides both broad-spectrum weed and broad-spectrum grass control and enhanced burndown with residual control.

Sandea

Recently receiving a new, supplemental label for use on blueberries, okra, rhubarb and other crops, Sandea is especially effective on nutsedge. Sandea is produced by the Gowan Co. and is effective in controlling a number of sedges and broadleaf weeds, and it is rainfast within four hours.


Tomatoes competing with weeds that may shade plant and delay or prevent ripening.
PHOTO COURTESY OF DR. TOM LANINI, UC DAVIS.

"It's very effective on both purple and yellow nutsedge," said Ken Muzyk of Gowan. Sandea works through the inhibition of the acetolactate synthase (ALS) enzyme. It is readily absorbed by roots and foliage and translocates throughout the plant.

Zeus

The new herbicide Zeus from FMC offers a triple benefit in that it provides control both as a preemergent treatment and for emerged sedge. Additionally, Zeus helps control tubers to help prevent future outbreaks. Zeus is approved in most states for use against weeds, annual grasses and sedges in asparagus, cabbage transplants, horseradish, mint and strawberries. Approval for use on other crops is pending. "It's very effective against nutsedge," said Robert Leifker, product manager.

Zeus is a light-dependent herbicide that disrupts lipid cell membranes. In doing so, the product inhibits the enzyme protoporphyrinogen oxidase, commonly abbreviated as protox. The lethal effect is actually caused by natural plant compounds that accumulate in the cells of the weeds treated with Zeus. Protox is the site of action, but induction of lipid peroxidation, which results in membrane disruption, is the mechanism of action.

Leifker noted that Zeus has low volatility and won't damage adjacent crops.

Zeus can be used to combat weeds that are resistant to glyphosate, imidazolinones and sulfonylurea acetolactate synthesis (ALS) inhibitors.

Fungicides

Fontelis

With the EPA label pending, and expected shortly, Fontelis from DuPont is a new fungicide that helps growers deal with unexpected weather conditions or other unforeseen circumstances that prevent application as planned. It provides broad-spectrum control of both foliar and soilborne diseases plus preventive, curative and residual activity.

"Fontelis brings power and flexibility to growers to deal with the unexpected," said Dr. Bond McInnes, DuPont fungicide technical manager. "Fontelis has the flexibility to be used on a wide range of vegetables, tree fruits and nut crops which is essential for growers managing a multicrop system." McInnes cited features of Fontelis suspension concentrate that include an ability to mix easily and spray cleanly. "It has excellent rainfastness," he said. "We're excited to bring Fontelis to the U.S. market. With the power and flexibility of Fontelis, growers have a new fungicide which provides excellent disease control essential for higher yields and quality."


Strawberry plants on left treated with Regalia as a pre-plant dip.
PHOTO COURTESY OF MARRONE BIO INNOVATIONS.

Torino

Currently awaiting registration, Torino from FMC has the active ingredient cyflufenamid, and is targeted for control of powdery mildew in cucurbits, grapes, pome fruit and strawberries. Leifker said, "It is a new, novel mode of action with translaminar activity. It has demonstrated control of all strains of powdery mildew, including those strains known to be resistant to other active ingredients. We expect registration this spring. "

Regalia

Pam Marrone, president of Marrone Bio Innovations, said, "Major expanded EPA labeling of our biofungicide Regalia includes approval for new soil applications."

The product is approved as a dip for strawberry or tomato transplants, and it enhances the natural ability of plants to fight fungal and bacterial diseases. Regalia controls soilborne diseases and improves root growth and plant growth when used as a pre-plant dip, injected through drip irrigation or used as a soil drench. Its use is expanding in specialty crop markets for disease control in tomatoes, peppers, citrus and walnuts, and mildew control in leafy greens, cucurbits, berries and vines.


Fontelis is approved to control gummy stem blight in cucurbit crops.
PHOTO COURTESY OF DUPONT.

Regalia contains a unique active ingredient from the extract of Reynoutria sachalinensis, or giant knotweed. It switches on natural defense mechanisms, causing them to produce and accumulate higher levels of natural proteins and other compounds that inhibit disease development.

Used in tank mixes, program rotations and stand-alone, Regalia controls diseases that include powdery mildew, downy mildew, botrytis gray mold, early blight, late blight and bacterial leaf spot. A minimal re-entry interval and a zero day preharvest interval provide growers with greater operational flexibility and a residue-free harvest.

Nancy Riggs is a freelance writer and frequent contributor. She resides in Mount Zion, Ill.