ALMOND: FUNGICIDE EFFICACY - CONVENTIONAL

FUNGICIDE EFFICACY - PHYTOPTHORA ROOT AND CROWN ROT (PRCR) USING CONVENTIONAL TREATMENTS

Rating: 5 = excellent and consistent, 4 = good and reliable, 3 = moderate and variable, 2 = limited and/or erratic, 1 = minimal and often ineffective, 0 = ineffective, NL = not on label, and ND = no data.

* Registration pending in California. **Not registered, label withdrawn or inactive in California.

¹ Code numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different Code number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode-of-actions (MOA) with high resistance risk before rotating to a fungicide with a different MOA (Code number); for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different MOA (Code number).

² Strains of the brown rot fungi Monilinia laxa and M. fructicola resistant to Topsin-M and T-Methyl have been found in some California almond orchards. MBC-resistant strains of the jacket rot fungus, Botrytis cinerea and powdery mildew fungi, have been reported in California on crops

other than almond and stone fruits and may have the potential to develop in almonds with overuse of fungicides with similar chemistry. MBC-resistant strains of the scab fungus, Venturia (Fusicladium, Cladosporium) carpophila, have been found in California.

³ Field resistance of Alternaria sp. and Fusicladium carpophilum to QoI and SDHI fungicides has been detected in almond orchards. AP-resistant populations of Monilinia spp. have been found on other stone fruit crops in California.

⁴ Of the materials listed, only sulfur, Abound, Gem, and some of the DMI fungicides (FRAC Code No. 3) are registered for use in late spring and early summer when treatment is recommended.

⁵ PM-like refers to a powdery mildew-like disease on almond fruit. Information suggests an Acremonium species is involved.

⁶ Excellent control obtained when combinations of Topsin-M or T-Methyl and Captan are used.

⁷ To reduce the risk of resistance development, start treatments with a fungicide with a multi-site mode of action; rotate or mix fungicides with different mode of action FRAC numbers for subsequent applications, use labeled rates (preferably the upper range), and limit the total number of applications per season.

⁸ Oils recommended include "light" summer oil, 1-2% volume/volume.

⁹ Not registered for use later than 5 weeks after petal fall.

¹⁰ Efficacy reduced at high temperatures and relative humidity.

¹¹ Bravo Ultrex, Bravo WeatherStik, Echo, Echo Ultimate, and Chlorothalonil are currently registered.

¹² Dormant applications with oil are highly effective against scab, Do not use in-season combinations with oil or shortly before or after oil treatment.

¹³ Efficacy is better in concentrate (80-100 gal/acre) than in dilute sprays.

¹⁴ The low rates necessary to avoid phytotoxicity in spring reduce the efficacy of copper.

¹⁵ "Burns out" scab twig lesions when applied at delayed dormant. (Chlorothalonil can be applied with dormant oil during tree dormancy).

¹⁶ Hull rot ratings are for the disease caused by Rhizopus stolonifer. Ratings for the disease caused by Monilinia or Aspergillus spp. will be provided in the future.

¹⁷ PlantShield is best used for wood-exposing wounds to prevent silverleaf and wood decay.

ALMOND: FUNGICIDE EFFICACY - BIOCONTROLS AND NATURAL PRODUCTS

Rating: 5 = excellent and consistent, 4 = good and reliable, 3 = moderate and variable, 2 = limited and/or erratic, 1 = minimal and often ineffective, 0 = ineffective, NL = not on label, and ND = no data.

* Registration pending in California.

** Not registered, label withdrawn or inactive in California.

¹ Alphabetically arranged organic treatments. Note that kasugamycin is a fermentation (natural) product, but not an organic treatment.

² ALS = Alternaria Leaf Spot caused by Alternaria alternata and A. arboresscens.

³ PM refers to a powdery mildew disease.

⁴ Hull rot ratings are for the disease caused by Rhizopus stolonifer.

⁵ FRAC Codes are also provided as BM- or P-number codes. In general, sulfur compounds are fungicidal and may affect applications of fungal biocontrols (e.g., Botector); whereas copper may affect applications of bacterial biocontrols (e.g., Actinovate, Double Nickel 55, and Serenade). Rotations must consider these factors.

⁶ Labeled for Eutypa sp., Botryosphaeria sp., Cytospora sp., and other trunk diseases of almond.

ALMOND: TREATMENT TIMING

Note: Not all indicated timings may be necessary for disease control.

Rating: 3 = most effective, 2 = moderately effective, 1 = least effective, and 0 = ineffective

¹ Two and five weeks after petal fall are general timings to represent early postbloom and the latest time that most fungicides can be applied. The exact timing is not critical but depends on the occurrence of rainfall.

² If anthracnose was damaging in previous years and temperatures are moderate (63°F or higher) during bloom, make the first application at pink bud. Otherwise, treatment can begin at or shortly after petal fall. In all cases, application should be repeated at 7- to 10-day intervals when rains occur during periods of moderate temperatures. Treatment should, if possible, precede any late spring and early summer rains. Rotate fungicides, using different fungicide classes, as a resistance management strategy.

³ Early treatments (during bloom) have minimal effect on scab; the 5-week treatment usually is most effective. Treatments after 5 weeks are useful in northern areas where late spring and early summer rains occur. Dormant treatment with liquid lime sulfur improves efficacy of spring control programs.

⁴ If pathogen spores were found during fall leaf monitoring, apply a shot hole fungicide during bloom, preferably at petal fall or when young leaves first appear. Reapply when spores are found on new leaves or if heavy, persistent spring rains occur. If pathogen spores were not present the previous fall, shot hole control may be delayed until spores are seen on new leaves in spring.

⁵ Dormant copper treatment seldom reduces shot hole infection but may be useful in severely affected orchards and must be followed by a good spring program.

⁶ Treatment in June is important only if late spring and early summer rains occur.

⁷ Make application at 1 to 5% hull split to manage hull rot caused by Rhizopus stolonifer; use earlier June timings for hull rot caused by M. fructicola. Apply a second application, mid-way through hull split especially if hull split is progressing slowly.

ALMOND: SUGGESTED DISEASE MANAGEMENT PROGRAMS BY FRAC¹ CODES - CONVENTIONAL GROWERS

Note: Not all indicated timings may be necessary for disease control (see Treatment Timing Table). If treatments are needed based on host phenology, weather monitoring, inoculum models, or environmental-disease forecasting models, suggested fungicide Codes are listed for each timing.

How to use this table:

1)Identify the disease(s) that need(s) to be managed. Know the disease history of the orchard, especially from the last season.

2)Select one of the suggested fungicide Codes. Numbers separated by slashes are pre-mixtures, whereas numbers separated by pluses are tank mixtures. If several diseases need to be managed, select a Code that is effective against all diseases. Refer to the fungicide efficacy table for fungicides belonging to each FRAC Code. Code numbers are listed in numerical order within the suggested disease management program.

3)Rotate Codes for each application within a season and, if possible, use each Code only once per season, except for multi-site mode-of-action materials (e.g., M2).