UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION TREE TOPICS

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1 UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION TREE TOPICS INFORMATION FOR TREE FRUIT AND NUT GROWERS IN CALIFORNIA S CENTRAL COAST REGION APRIL 16, 2010 VOLUME 35, ISSUE 2_ IN THIS ISSUE: SPOTTED WING DROSOPHILA CHERRIES BROWN ROT - APRICOTS FUNGICIDE EFFICACY APPLES WALNUT BLIGHT- WALNUTS Drosophila suzukii male Cherry with puncture Drosophila suzukii - larva SPOTTED WING DROSOPHILA (SWD) Spotted Wing Drosophila (Drosophila suzukii) remains a major threat to local cherry production after our first experience with it in cherries last year. This insect has the potential to devastate not only cherries but also most berries (strawberries, blackberries, raspberries, blueberries) plus many other fruits. Infestations are widespread throughout California and Oregon with some found in Washington, British Columbia and Florida. Walnuts and apricots do not appear to be targets at this point but there is the potential to infest tree-ripe apricots. Information is limited on apples but apples damaged from some other source such as codling moth or birds might be susceptible. For cherries, we know that the fruits become susceptible when they first begin to have a pink blush several weeks before harvest. Straw-colored fruits do not appear to be susceptible from recent work done by Dr. Bob Van Steenwyk at UC Berkeley. However, pink-blushed fruits were very susceptible.

2 The choice of insecticides and the timing of sprays will be critical but our first replicated field research on control will be conducted this spring in Santa Clara and San Joaquin Counties. Certainly, all aspects of control have not been fine-tuned at this point. In research projects we are varying from one pre-harvest spray to six. For growers, the best recommendation is to do what they do in Japan three or four pre-harvest sprays to knock the population back. The first spray is post-bloom around the latter part of April in our area possibly with a mildew or aphid spray. The second spray is when the fruit are in the straw-colored stage, possibly timed with a Gibberellin spray, about three weeks before harvest. A third or fourth spray just before harvest may be justified based upon trap counts. Watch out for the pre-harvest interval for insecticides on your early-ripening pollinizers if you intend to harvest them. We do not know for sure whether pre-harvest sprays will carry us through the end of harvest without some damage. Midharvest sprays of short-phi materials have not been tested except for GF-120 which did not provide adequate control last year of high fly populations with grower-applied treatments. Insecticide choice will be based upon current California registration, efficacy or effectiveness of the material, the pre-harvest interval (PHI), the re-entry interval (REI), the maximum residue level (MRL) and possibly closed-cab requirements. For export markets, the MRL is critical since few of the available, effective insecticides meet the requirements of all major export markets. Work with your packer to determine an acceptable spray program for export markets. For integrated pest management purposes, the choice of materials should not increase populations of other pests such as mites and should involve alternation of materials to help prevent pesticide resistance. Our chart of possible insecticides is found at our UC IPM web site at or in my February Tree Topics newsletter. This is not necessarily a complete listing or recommendation. There have been occasional problems with phytotoxicity following malathion use so follow label directions closely. Limited testing of insecticides has shown good control of SWD with organophosphates (malathion, diazinon), synthetic pyrethroids (but not plant-derived pyrethrins) and spynosyns (Delegate more so than spinosad). We should have much more information on efficacy after this season. The success or failure of your own control program will provide important information so keep a record of your observations. We are using white carton traps similar to those used by Deli s. We have drilled 3/16 inch holes that are scattered around the outside perimeter of the side of the top of the trap. They are usually baited with about one inch of apple cider vinegar although white wine may also work. A drop or two of soap mixed in may help with trap catches. If you only need one or two traps, I successfully used Rescue Fly Traps last year. Eliminate the house fly bait and substitute apple cider vinegar. Place the traps at three to five feet in height hanging from a lower limb. Look only for male flies that are tan with one spot on the trailing edge of each wing. There are some black flies with two spots on each wing, so be sure to properly identify your catches. If you catch any SWD, you have a problem. Populations can build up very rapidly. BROWN ROT APRICOTS There has been an unusual amount of brown rot in some apricot orchards this year. This is due to a combination of heavy rains and inadequate fungicide protection. Some growers skipped sprays because of poor weather conditions for spraying or to save money. This was not a year to skip sprays. There is damage to next years fruiting wood as well as lots of spores for possible fruit rot

3 problems at harvest. I have attached some information on fruit brown rot from our UC IPM Apricot Pest Management Guidelines. You may view the whole guideline at the UC IPM web site at This is usually only a problem if we get rainfall or high humidity just before harvest. A good brown rot control program will be a necessity next year at red bud and full bloom. FUNGICIDE EFFICACY AND TIMING - APPLES Who knows how the spring rainfall will last this year? Keep up with your scab and mildew sprays as well as fire blight if you are in a warmer location where it has been a past problem. Fire blight is often a problem as temperatures warm up in late bloom. I have attached the apple section of our Fungicide and Efficacy Timing publication. It can be found in its entirety at WALNUT BLIGHT WALNUTS We are still in walnut blight season with the continued spring rainfall. The Spring, 2010 issue of the Sacramento Valley Walnut News included some great information on walnut blight which I have re-printed later in this newsletter. The whole issue as well as previous issues may be viewed at William (Bill) W. Coates Acting County Director Univ. of Calif. Cooperative Extension Farm Advisor, Fruit and Nut Crops 649 San Benito Street, Suite 115 San Benito, Santa Cruz, Santa Clara Hollister, CA and Monterey Counties (DO NOT USE ABOVE ADDRESS FOR MAIL) (831) phone Mail: P.O. Box 1956 (831) FAX Hollister, CA bwwcoates@ucdavis.edu web: For those without Internet access, call or write to me and I will provide hard copies of any information mentioned above. Reference to commercial products or trade names is with the understanding that no discrimination is intended, and no endorsement by Cooperative Extension is implied. The University of California prohibits discrimination or harassment of any person on the basis of race, color, national origin, religion, sex, gender identity, pregnancy (including childbirth, and medical conditions related to pregnancy or childbirth), physical or mental disability, medical condition (cancer-related or genetic characteristics), ancestry, marital status, age, sexual orientation, citizenship, or status as a covered veteran (covered veterans are special disabled veterans, recently separated veterans, Vietnam era veterans, or any other veterans who served on active duty during a war or in a campaign or expedition for which a campaign badge has been authorized) in any of its programs or activities. University policy is intended to be consistent with the provisions of applicable State and Federal laws. Inquiries regarding the University's nondiscrimination policies may be directed to the Affirmative Action/Staff Personnel Services Equal Opportunity Director, University of California, Agriculture and Natural Resources, 1111 Franklin Street, 6th Floor, Oakland, CA , (510) U.S. DEPARTMENT OF AGRICULTURE, UNIVERSITY OF CALIFORNIA AND SAN BENITO COUNTY COOPERATING

4 UC IPM Pest Management Guidelines - APRICOT RIPE FRUIT ROT (11/07) Pathogens: Monilinia fructicola, Monilinia laxa SYMPTOMS Dark brown, firm, circular spots spread rapidly over fruit, and tan spore masses form in the centers of spots. Ripening fruit is most susceptible. Diseased fruits may remain on the tree until the next season. COMMENTS ON THE DISEASE Fruit rot is not as important as blossom blight in California apricots. Warm rains near harvest can lead to fruit rot infection in a few hours. At 67 F, fruit rot symptoms will appear within 48 hours of rain. MANAGEMENT The need for preharvest treatment depends upon the weather; the threat of rain or heavy dews in the last 2 to 3 weeks before harvest may signal the need for protection. Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program (see FRUIT SAMPLING AT HARVEST). Record results (sample form available online). Common name (trade name) Amount/Acre R.E.I.+ (hours) P.H.I.+ (days) When choosing a pesticide, consider the general properties of the fungicide as well as information relating to environmental impact. Caution: Never apply sulfur to apricot trees or captan to apricot fruit. PREHARVEST A. PROPICONAZOLE (Bumper, Orbit) 4 fl oz 24 0 MODE OF ACTION GROUP NAME (NUMBER 1 ): Demethylation inhibitor (3) B. FENBUCONAZOLE (Indar) 75WSP 2 oz 12 0 MODE OF ACTION GROUP NAME (NUMBER 1 ): Demethylation inhibitor (3) COMMENTS: Apply a minimum of 50 gal water/acre. A protectant fungicide. Begin applications before infections occur if conditions are conducive to disease development. Do not apply more than 1 lb of formulated product/acre/season. C. PYRACLOSTROBIN/BOSCALID (Pristine) oz 12 0 MODE OF ACTION GROUP NAME (NUMBER 1 ): Quinone outside inhibitor (11) and Carboxamide (7) D. THIOPHANATE METHYL (Topsin M) 70WP 0.5 lb/100 gal water up to 1.5 lb/acre 12 1 MODE OF ACTION GROUP NAME (NUMBER 1 ): Methyl benzimidazole (1) COMMENTS: Apply only once per year. If thiophanate methyl was used earlier for brown rot or powdery mildew control, do not use it for control of ripe fruit rot. Check with your processor before using this material. Strains of Monilinia fructicola resistant to thiophanate methyl have been found in California apricot orchards. If resistance has occurred in your orchard, do not use this fungicide. E. MYCLOBUTANIL (Rally) 40WSP oz 24 0 MODE OF ACTION GROUP NAME (NUMBER 1 ): Demethylation inhibitor (3) COMMENTS: Do not apply more than 2.75 lb/acre/season. F. FENHEXAMID (Elevate) 50WDG lb 12 0 MODE OF ACTION GROUP NAME (NUMBER 1 ): Hydroxyanilide (17) COMMENTS: Do not apply more than 6 lb/acre/season. Ripe Fruit Rot (11/07) 52 Illustrated version:

5 UC IPM Pest Management Guidelines - APRICOT Common name (trade name) Amount/Acre R.E.I.+ (hours) P.H.I.+ (days) G. CYPRODINIL (Vangard) 75WG 10 oz 12 2 MODE OF ACTION GROUP NAME (NUMBER 1 ): Anilinopyrimidine (9) COMMENTS: Efficacy is reduced under conditions of high temperatures (high 90s and above) and high humidity. POSTHARVEST A. FLUDIOXONIL (Scholar) 50WP 8 16 oz/7 100 gal water 0 0 MODE OF ACTION GROUP NAME (NUMBER 1 ): Phenylpyrrole (12) COMMENTS: Treats 200,000 lb fruit using a spray-application system. Do not make more than one postharvest application to the fruit. + Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. 1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see Fungicides with a different group number are suitable to alternate in a resistance management program. For fungicides with mode of action Group numbers 1, 4, 9, 11, or 17, make no more than one application before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number. Ripe Fruit Rot (11/07) 53 Illustrated version:

6 APPLE AND PEAR: FUNGICIDE EFFICACY Resistance Scab Powdery mildew Fungicide risk (FRAC#) 1 Protectant Eradicant (apple only) Adament medium (3/11) Bayleton high (3) Distinguish** medium (9/11) Inspire Super medium (3/9) Flint 2 high (11) Pristine medium (11/7) ND Procure 4 high (3) Rally 5 high (3) Rubigan 4 high (3) Scala high (9) Sovran high (11) Syllit medium (M7) Tebuzol high (3) Topsin-M/T-Methyl high (1) /Thiophanate-Methyl 3 Vangard high (9) Ph-D* medium (19) Captan 6 low (M4) Dithane/Manzate/ low (M3) Penncozeb 6 Maneb** low (M3) Thiram 5 low (M3) Ziram 6 low (M3) Copper 6 low (M1) Lime sulfur 6,8 low (M2) Sulfur 7 low (M2) Bactericide/ Resistance Fire blight 11 Biological risk Contact Systemic Phytotoxicity Ag Streptomycin Agri- Mycin /Firewall high /- MycoShield(FireLine 10 ) high /- (FlameOut**) Copper 7 low (M1) Captan 6 low (M4) Dithane/Manzate/ low (M3) Penncozeb 6 Blight Ban low /- Bloomtime Bio low /- Rating: ++++ = excellent and consistent, +++ = good and reliable, ++ = moderate and variable, + = limited and/or erratic, +/- = minimal and often ineffective, ---- = ineffective. * Registration pending in California **Not registered, label withdrawn or inactive 1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number. 2 Label withdrawn on pears because of resistance development. 3 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/season. Continued on next page... Apple and Pear: Fungicide Efficacy and Treatment Timing 23

7 Apple and Pear Fungicide Efficacy, continued 4 On pear, use only before white bud and after full bloom. 5 Labeled on apple only in California. 6 These materials show some efficacy and should be used in mixtures with antibiotics as a component of resistance management programs. Captan is registered on apples, whereas Dithane is registered on apples and pears. 7 Copper, though effective for scab and blight control, causes fruit scarring. 8 "Burns out" scab twig lesions when applied at delayed dormant and disrupts pseudothecial (or ascostroma) development when applied to leaves in fall. CAUTION: LIME SULFUR IS INCOMPATIBLE WITH MOST OTHER PESTICIDES WHEN USED AFTER BUDBREAK. CHECK BEFORE USE. 9 In-season application eradicates powdery mildew. 10 Labeled on pear but not on apple. 11 Growth regulators such as prohexadione calcium (Apogee) can be used in an integrated approach to reduce host susceptibility but do not have antibiotic activity against fire blight. Thus, Apogee was not included in the fire blight activity ratings. APPLE AND PEAR: TREATMENT TIMING Note: Not all indicated timings may be necessary for disease control. Disease Fall Delayed dormant Green tip Pink bud Spring Scab Powdery mildew Fire blight Rating: +++ = most effective, ++ = moderately effective, + = least effective, and ---- = ineffective 1 Protection of early tissue is important. Additional applications should be made according to infection periods as determined by the Mills table. 2 Disruption of pseudothecial (or ascostroma) development (fall) and inactivation of overwintering twig lesions (delayed dormant) occurs; effects of these treatments on disease control uncertain. 3 Early application is most effective; added treatments are made if mildew continues. 4 Start management program at the beginning of bloom and continue through bloom including "rat-tail" bloom throughout spring. Several models are available for forecasting infection periods and treatment timing. Models include: Maryblyt, Cougar Blight, etc. Apple and Pear: Fungicide Efficacy and Treatment Timing 24

8 University of California Technical Bulletin Walnut Blight Management Update Growing Season J. E. Adaskaveg, University of California, Riverside, R. Buchner, and J. Connell, UCCE, Tehama and Butte Co., respectively Walnut blight is caused by the bacterium Xanthomonas arboricola. Copper was the sole material available for managing this devastating leaf and fruit disease since the inception of modern walnut production in California. In the early 1990s, copper resistance developed in the pathogen populations and the disease began causing significant crop losses in many orchards in the central and northern production areas of the state. Research at the University of California (UC) showed that the disease could still be managed when copper was mixed with an ethylene bis-dithiocarbamate or EBDC fungicide such as maneb (e.g., Manex-DuPont Crop Protection). Since the early 1990s, the California Walnut Commission has successfully petitioned the United States Environmental Protection Agency (US-EPA) for an emergency registration of Manex (one of the longest standing Section 18s in the history of US agriculture). While the EPA was concurrently reviewing the registration of the entire class of EBDC pesticides, the California Walnut Board aggressively funded UC research to better understand the epidemiology of the disease and management practices including alternative treatments for Manex. In 2009, as part of a joint decision between the US-EPA and the EBDC task force (a coalition of registrants and manufacturers of EBDC products), the United States registration of maneb, which is used to manufacture Manex, was canceled. Fortunately, UC research has identified several alternative products ranging from fungicides, an antibiotic, and organic compounds. A closely related EBDC compound, mancozeb, was identified that could be a drop in replacement for maneb. With over 18 years of experience with copper and EBDC materials for managing walnut blight, mancozeb was the logical choice for pursuing an emergency registration for commercially managing blight. The California walnut industry has successfully petitioned the US-EPA for an emergency registration of mancozeb and the California Department of Pesticide Regulation has issued a Section 18 Exemption on February 25, 2010 to allow applications of DuPont Manzate Flowable or Manzate Pro-Stick in combination with copper on walnut in selected California Counties. Either product must be tank mixed with a fixed copper product registered for use on walnut in California. The US EPA has not established a time limited tolerance but expects to do so in the near future. If residues are found on walnut at the time of harvest and a tolerance has not been issued, the residue levels will be considered illegal. Both Manzate formulations are very similar to Manex however they are coordinated EBDC, i.e., a defined mixture of zinc and manganese is used in the manufacturing of the active ingredient (Zn- and Mn- EBDC). This fungicide/bactericide has been registered in the United States for over 50 years and provides broadspectrum disease control. Both Manzate Pro-Stick and Manzate Flowable, when tank mixed with copper, are highly effective for managing bacterial plant diseases. Table 1 compares the properties of Manex and Manzate Pro Stick. Note that Manex is no longer legal to apply on California walnut. In summary, Manzate Pro-Stick plus copper or Manzate flowable plus copper have been shown to be equivalent to Manex plus copper for managing walnut blight (Fig. 1). Over the last four years, more than 20 research trials have been conducted in Tehama, Butte, Solano and Fresno Counties evaluating Manzate Pro-Stick, Manzate Flowable other mancozeb products, and alternative treatments.

9 Issue 6, Spring Sacramento Valley Walnut News Walnut Blight Control Experience over the Last 20 years Richard P Buchner, Tehama County farm Advisor 1) Complete walnut blight research information is available at the UC Fruit and Nut information center 2) Consider First blight application when 40 percent of the pistillate buds have expanded to the prayer stage. 3) Copper tank mixed with a section 18 ethylene bis-dithiocarbamate (EBDC) product is currently the most effective spray choice. For 2010, the two available EBDC products are DuPont Manzate flowable or Manzate Pro-Stick. Be aware of application issues if a time limited tolerance is not issued by the US EPA. Tolerance information changes quickly so check with your walnut buyer before application. 4) Full coverage at full material rates is suggested. Under severe walnut blight infection pressure, excellent coverage at the correct application rate is advised. 5) Good quality copper products are all effective for controlling walnut blight. Follow label rates because metallic rates and copper availability vary depending upon the manufacturer. 6) Following the first application, consider damage history and weather forecasts for additional spray decisions. Sprays are thought to provide protection for 7 to 10 days. 7) Computer weather forecasts ( and or Xanthocast (Irrigate.net or Agtelemetry.com) are available. Weather channels forecast weather conditions and Xanthocast developed By Dr. Jim Adaskaveg at UC Riverside can help determine disease infection events. Prayer Stage Cooperative Extension Sutter Yuba Counties 142A Garden Highway, Yuba City, CA Office (530) Fax (530)

10 TREE TOPICS NEWSLETTER APRIL 16, 2010