Disease Control Programs For Almonds

Beth L. Teviotdale
Extension Plant Pathologist
University of California Davis/Kearney Agricultural Center

John Edstrom
Farm Advisor
UCCE Colusa County

Almond trees are treated annually for protection against an array of plant diseases. Along with the several diseases growers face, there is a list of fungicides from which to choose. Making decisions about fungicide choice and treatment timing for any given disease may have an effect on other diseases as well. Thus it is important to select fungicides that are effective against diseases known to be in the orchard and to apply them at the correct time.

Our objective with this research has been to evaluate various fungicide programs and new fungicides for effectiveness against several diseases.

Among the three fungicide programs tested in which treatments were made at pink bud (PB) and full bloom (FB), the Rovral® + oil (PB, FB) and the Rovral® + oil (PB) and Break® (FB) programs were superior to the Rovral( + oil (PB) and Abound® (FB) program. Although these three programs did not differ statistically for leaf blight control, the Rovral® + oil (PB) and Abound (FB) program provided numerically better control of leaf blight.

Break®, Flint®, Indar®, and Stratego® (a combination of the active ingredients in Break® and Flint®) were the most effective in controlling brown rot. The strobilurin fungicides Abound®, Flint®, and Stratego® were best for leaf blight control. Mirage® (a citrus oil compound) and QST® (a biological control agent) were ineffective against both diseases.

Spring of 1999 was relatively dry, thus disease levels were correspondingly lower. Scab, shot hole and rust diseases did not occur in this orchard this year.

Growers should plan a fungicide program that protects against brown rot during bloom and shot hole, scab, leaf blight and perhaps anthracnose later in the season. Trees are most susceptible to brown rot at full bloom so early timings should include a spray at or near full bloom. Later applications are aimed at the other diseases. Late bloom and post bloom fungicide choices should include at least one material with a broad spectrum of activity. Even though disease levels were relatively low in 1999 and inoculum levels for 2000 may also be reduced, any of these diseases could erupt if weather is favorable. Therefore, a carefully planned and executed fungicide program is important.

Table 1.
Effects of fungicide treatment on brown rot blossom blight (Monilinia laxa) and leaf blight (Seimatosporium leichenicola) of cv Butte almond trees, Colusa County. 1999.

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Copyright © 1999 Colusa County Cooperative Extension, Univ. of California
Last modified: September 01, 2000