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RFCG032 2001 Florida Citrus Pest Management Guide: Schedule for Timing of Fungicides for Disease Control1 L.W. Timmer2 1. This document is Fact Sheet RF-CG032, part of the 2001 Florida Citrus Pest Management Guide, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Date printed: September 1997. Date revised: October 2000. For a copy of this handbook, request information on its purchase at your county extension office. Please visit the EDIS Web site at http://edis.ifas.ufl.edu. 2. L.W. Timmer, professor, pathologist, Citrus REC, Lake Alfred, Florida, a branch campus of the University of Florida; Plant Pathology Department; Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean. Disease control has become progressively more difficult as our choices for effective fungicides have dwindled. One possible way to compensate for the loss of some of our fungicides is to take advantage of our available fungicides by better timing. The timing of any citrus fungicide depends on one of three methods: applications by the calendar, flowering or bloom and growth flush. In the accompanying chart, the first row at the top represents the months of the calendar, the second row is bloom periods (Early, Peak, and petalFall) and the third row is flush (25%, 50%, and 75% expansion). To demonstrate how the chart is set up, notice that greasy spot spray applications do not have any shading in rows describing different disease situations. Thus, all spray applications are based on the calendar. Timing for Melanose on grapefruit option1 is a dark shade indicating timing based on petal-fall, not the second week in April. An example of timing based on bloom (dark shading) is a light infestation of Scab. Here the timing is based in the period after petal-fall followed with 2 or 3 additional spray applications at 3-week intervals. For a heavy infestation of Scab, the first spray is based on the spring flush (light shading), between 25% and 50% flush expansion. The next scheduled spray is based on the bloom (dark shading) which is immediately after petal-fall. The timing for bloom and flush is entirely dependent on when the growth occurs, not on the calendar. Thus, spray applications will be adjusted forward or backward for varieties or locations where bloom and spring flush is earlier or later. Note: Letters in boxes indicate the most appropriate fungicides, such as C = copper and B = Alternative sprays of Benlate and Ferbam. Recommended Chemical Controls READ THE LABEL. See Table 1. Rates for pesticides are given as the maximum amount required to treat mature citrus trees unless otherwise noted. To treat smaller trees with commercial application equipment including handguns, mix the per acre rate for mature trees in 250 gallons of water. Calibrate and arrange nozzles to
2001 Florida Citrus Pest Management Guide: Schedule for Timing of Fungicides for Disease.... 2 deliver thorough distribution and treat as many acres as this volume of spray allows.
2001 Florida Citrus Pest Management Guide: Schedule for Timing of Fungicides for Disease.... 3 Table 1. Schedule for Timing of Fungicides for Disease Control Months Feb March April May June July August Greasy Spot: Foliage Susceptible OR Heavy Infestation I I C or C-Oil Oil or C-Oil Tolerant OR Light Infestation I I C or C-Oil Greasy Spot: Fresh Grapefruit C 1. Susceptible Grapefruit, Hamlin, Pineapple, and Tangelo. 2. Tolerant Valencia, Murcott, Tangerine, and Tangerine Hybrids. 3. I = Inspect for leaf-drop caused by greasy spot. 4. A single application of copper is more effective early in the season when using two sprays. Melanose: Fresh, Only Orange/Tangerine C Bloom: (Early, Peak, petal-Fall) E P F Grapefruit Option 1 C C C Grapefruit Option 2 # C C C 1. Option1: Apply copper 2 wks after petal-fall and reapply at 3-wk intervals. *A greasy spot spray during this period will also control Melanose. 2. Option2: # A Benlate spray at petal-fall to control scab will also control Melanose, then copper at 3-wk intervals. Scab: Fresh, Only Bloom: (Early, Peak, petal-Fall) E P F
2001 Florida Citrus Pest Management Guide: Schedule for Timing of Fungicides for Disease.... 4 Table 1. Schedule for Timing of Fungicides for Disease Control Months Feb March April May June July August Flush Expansion: 25% 50% 75% Light Infestation B C Heavy Infestation B B C C 1. Light Infestation: Use Benlate or Carbamate after petal-fall with copper as a 2nd application. 2. Heavy Infestation: Use Benlate or Carbamate at 1/4 to 1/2 expansion of flush. May alternate either Benlate, Carbamate or copper at early postbloom. For multiple applications use copper at low rates scheduled every 2-3 wks. Alternaria: Bloom: (Early, Peak, petal-Fall) E P F Flush Expansion: 25% 50% 75% Light Infestation C C C Heavy Infestation C C C C C C 1. Light Infestation: Schedule sprays at petal fall and then 2 monthly applications. 2. Heavy Infestation: Schedule copper sprays at 1/4 to 1/2 expanded flush, after petal fall, then every 1-1/2 3 wks depending on rainfall and disease pressure. Postbloom Fruit Drop: 1. See Postbloom Fruit Drop chapter in this publication for predictive model to determine whether sprays are needed and the proper timing. Use Benlate or Benlate + Ferbam.