IN YOUR ORCHARD
done at 40% open flowers. Under high disease pressure, a pink bud (5% open flowers) followed by a full bloom (80% open flowers) application is suggested. Dr. Jim Adaskaveg, has done a great job authoring the ‘Fungicide Efficacy’ document and has put together a color guide (ucanr.edu/sites/sayalmond/Almond_Publications) that shows the symptoms of different diseases.
products significantly reduced disease. Among products evaluated, however, Kocide 3000, Badge X2, Champ- Ion2+, and Cuprofix were more effective than Cueva. A single delayed dormant (copper-mancozeb) and a single in-season treatment (copper alone or copper+mancozeb) in mid-March timed before rainfall and warm conditions provided excellent control and was equivalent to five applications (delayed dormant and four applications in 10- to14-day intervals starting at full bloom) using the same chemicals. For organic growers, Actinovate and Serenade also reduce bacterial spot, although not as effectively as copper products. For better control, Serenade should be mixed with copper. Avoid high-angle sprinkler irrigation; continued wetting of the foliage and fruit into the season will allow bacterial spot to increase in incidence and negate your springtime program. Every year is different and IPM practices should be followed to determine the best timing and material to spray. Growers often concentrate their control measures on brown rot sprays at first bloom and often neglect their scab and Alternaria sprays that are typically done at two to five weeks after petal fall. Everyone is anxious to spray Nonpareil at pink bud which is the least important time to spray this most disease-resistant variety, yet cultivars Monterey and Carmel are often not sprayed for scab. Two sprays are made for brown rot control under high disease pressure. The first is usually done at pink bud (5-10% bloom) using a systemic fungicide such as a DMI (FRAC 3) or AP (FRAC 9). The second spray should be done near 80% (full bloom) or seven to ten days after the first spray. This is the most effective brown rot spray program! Depending on the weather, a third spray may be necessary for protecting against jacket rot and green fruit rot caused by Monilinia , Botrytis , and Sclerotinia species. Try to reduce the potential of resistance by using a multi-site compound (such as ziram, chlorothalonil, captan, or mancozeb). Application techniques are important. Ground applications are better than air, but care must be taken that both are applied correctly. In general, use properly calibrated and
Bacterial spot, Xanthomonas arboricola pv.
pruni , was found and identified in the Northern San Joaquin Valley in 2013. Symptoms of infected nuts include the production of an amber colored gum from spots on the hull. We initially recommended trying to reduce inoculum levels
Bacterial Leaf Spot symptoms Xanthomonas
by defoliating leaves with zinc sulfate in the fall, destroying mummies, and spraying fall, dormant, or delayed dormant copper treatments to reduce overwintering inoculum. More recently, Dr. Adaskaveg has conducted field trials on bacterial spot, primarily on the susceptible ‘Fritz’ variety that has included dormant and in-season applications. Late- dormant treatments (late January) with copper or copper- mancozeb significantly reduced disease incidence. Early dormant treatments that were applied in mid-November or mid-December were effective in low rainfall years. In-season treatments starting at full bloom through petal fall were most effective when timed around rain events and before temperatures started to increase above 77°F (25°C) in the springtime. Copper treatments were applied by halving the rate with each successive application (e.g., 1, 0.5, 0.25 lbs MCE/A — metallic copper equivalent/ acre). No copper phytotoxicity or only minor leaf spotting with no leaf drop was observed after four applications when copper rates were successively reduced. All copper
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