After a 20 Year “Emergency” California Walnut Growers Can Rest Easy With Full Fungicide Registration

Walnut Blight Spraying

Walnut Blight Spraying

For 20 years, California walnut growers had to convince the EPA to grant a temporary emergency registration for a fungicide to control annual outbreaks of walnut blight. At the same time, the growers assembled the data necessary to make a full registration possible. After 20 years, the EPA granted the full registration and the walnut growers can rest easy.

“Depending on variety, walnut blight can take a heavy toll on walnut production, particularly when inoculum is high and spring weather is warm and wet.

However, with the federal EPA granting Manzate (flowable or dry flowable formulations) a Section 3 registration last year, walnut growers throughout California now have a reliable option for controlling the disease. For the previous two decades, growers in the state could use this and other ethylene bis-dithio-carbamates (EBDCs) products to treat for walnut blight only in selected counties under a Section 18 (emergency exemption) registration. Applying for Section 18 registration required submitting extensive environmental, health and safety data each year.

The walnut blight bacterium (Xanthomonas arboricola pv juglandis) over-winters in dormant buds primarily under the outer bud scales or cataphylls. When buds break in the spring, cataphylls open and young shoots extend past them. Rain drops spread the disease by splashing bacteria onto any green tissue, infecting them.

The disease appears as black lesions on green tissue. As bacteria spread inside the walnut, they grow toward the center of the nut early in the season, destroying the developing kernel.

In orchards with histories of walnut blight damage, protective treatments at seven to 10-day intervals during prolonged wet springs are necessary for adequate disease control.”

Author: Northcutt, G.
Affiliation: Reporter.
Title: Tips for better control of walnut blight.
Source: Western Farm Press. 2014-04-09. Available: http://westernfarmpress.com/tree-nuts/tips-better-control-walnut-blight

EPA Recognizes Value of Fumigants in Peanut Fields

Normal Peanuts and Black Rot Peanuts

Fumigated and Non-Fumigated

The disease known as cylindrocladium black rot (CBR) grows best in cool soils and is a major problem in the Virginia and North Carolina peanut regions. Entire pods may turn black and rot. The fungus may survive several years in the soil. Disease incidences in excess of 80% have occurred. The soil fumigant, metam sodium applied 8-10 inches below rows at least two weeks prior to planting has been the standard recommendation for control of CBR since 1985. Recently, the USEPA conducted a study of the value of metam sodium for peanuts and concluded that…

“Thus, the main benefit of metam sodium is that it permits cultivation of peanuts that would otherwise not be economically viable. …a large proportion of peanut acreage in the North Carolina-Virginia region depends on metam sodium simply to make production economically viable.”

Authors: A. Chiri, and T. J. Wyatt
Affiliations: EPA, Office of Pesticide Programs, Biological and Economic Analysis Division.
Title: Assessment of the Benefits of Soil Fumigation with Metam Sodium in Peanut Production.
Publication: U.S. EPA. (2007). Assessment of the benefits of soil fumigation with metam sodium in peanut production (DP#337490). Available at http://www.regulations.gov/#!home