pecan scab control
TRANSCRIPT
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PECAN SCAB CONTROL
Monte Nesbitt, Extension Horticulture Texas A&M University
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RECIPE FOR SCAB INFECTION
Ò Susceptible Host Ò Disease inoculum
present in the orchard/air.
Ò Warm temperatures (>57 F) (80-90 F optimal)
Ò Site features affecting speed of foliage drying. É Bottomland/Upland É Crowding & Vegetation
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HIGH SCAB PRESSURE SITE
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INFECTION PROCESS
Step 1-Germination of scab spores requiring free moisture on the plant tissue surface (Latham & Rushing, 1988).
10-36 hours Variety/host resistance-affected Late afternoon rains with foliage remaining wet all night.
Step 2-Growth of the fungus into the pecan tissue, which requires dissipation of that free moisture but high relative humidity (Yates, et al., 1996).
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CAN YOU GET SCAB IN DRY AREAS WITH NO INOCULUM………………………..IN AN UNUSUALLY WET YEAR??
Seminole, Texas
Farwell, Texas
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Ò Infects leaves and stems, and can cause foliage loss and stem dieback. É Only infects
herbaceous, soft tissue.
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SEVERITY ON NUTS DEPENDS ON VARIETAL RESISTANCE & EARLINESS/LATENESS OF INFECTION
Nut Drop
Nut Shape, Size & Weight
Kernel Percentage
Shuck Opening
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Resistant (+) Susceptible (v)
Kanza ++++++++++ Sioux +++vvvvvvv
Lakota ++++++++++ Nacono +++vvvvvvv
Elliott ++++++++++ Kiowa +++vvvvvvv
Apalachee +++++++++v Choctaw ++vvvvvvvv
Caddo ++++++++vv Cheyenne ++vvvvvvvv
Oconee ++++++++vv Hopi +vvvvvvvvv
Forkert +++++vvvvv Waco +vvvvvvvvv
Prilop +++++vvvvv Tejas vvvvvvvvvv
Desirable ++++vvvvvv Western vvvvvvvvvv
Pawnee ++++vvvvvv Wichita vvvvvvvvvv
RECOMMENDED FOR EAST TEXAS
NOT RECOMMENDED FOR EAST TEXAS
PECAN VARIETIES DIFFER IN SUSCEPTIBILITY & STRAINS OF SCAB VARY BY LOCATION
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} Excellent scab resistance
} Good kernel quality } Nut size varies with
moisture ◦ 59 per lb; 52% kernel ◦ Thick shell; thinner than
Elliott } Good tree form } Yields well on young
and older trees alike
KANZA
2011 Brownwood, TX
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OVER TIME AND IN HIGH PRESSURE SITUATIONS, MODERATE RESISTANCE IN VARIETIES MAY DIMINISH
Sumner
Jackson
Choctaw
Cape Fear
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CONTROL
Ò Resistant Varieties Ò Wide Spacing, Good Airflow Ò Fungicide Treatment
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FUNGICIDES ARE TIMED TO COAT NEW LEAF AND NUT TISSUE WITH PROTECTIVE FUNGICIDE.
Budbreak to Post-Pollination: Sterol Inhibitor or Strobie every 10-14 days.
Post-Pollination to Shell Hardening: TPTH every 14-21 days.
Basic Program
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Active Ingredient FRAC GROUP
Tradename(s)* Max product per acre per application and total product per acre allowed per year**
Azoxystrobin 11 Abound (Syngenta) 12 oz/A; 73.8 oz/A/yr
Azoxystrobin + Difenconazole 11,3 Quadris Top (Syngenta) 14 oz/A; 56 oz/A/yr
Azoxystrobin + Propiconazole 11,3 Quilt (Syngenta), Quilt Xcel (Syngenta)
27.5 oz/A; 122 oz/A/yr 21 oz/A; 115 oz/A/yr
Dodine 12 ELast 400 (Aceto) 3 pt/A; 18 pt/A/yr Fenbuconazole 3 Enable 2F (Dow) 8 oz/A; 48 oz/A/yr Kresoxim-methyl 11 Sovran (BASF) 4.8 oz/A; 14.4 oz/A/yr
Metconazole 3 Quash (Valent) 3.5 oz/A; 14 oz/A/yr Phosphorus acid 33 Phostrol 5 oz/A; n/a Propiconazole 3 Orbit (Syngenta), Bumper (MANA), Tilt (Syngenta),
Propimax (Dow), others 8 oz/A; 32 oz/A/yr
Propiconazole + Trifloxystrobin 11,3 Stratego (Bayer) 10 oz/A; 30 oz/A/yr
Pyraclostrobin 11 Headline (BASF) 7 oz/A; 28 oz/A/yr Pyraclostrobin + Boscalid 11,7 Pristine (BASF) 14.5 oz/A; 58 oz/A/yr
Tebuconazole 3 Tebuzol (UPI), Folicur (Bayer), Toledo (Rotam), Monsoon (Loveland), Orius 3.6 F (MANA)
8 oz/A; 32 oz/A/yr
Tebuconazole + Azoxystrobin
11,3 Custodia (MANA) 17.2 oz/A; 69 oz/A/yr
Tebuconazole + phosphorous acid
3, 33 Viathon (Helena) 2.5 pts/A; 16.5 pts/A/yr
Tebuconazole + trifloxystrobin 11,3 Adament (Bayer), Absolute (Bayer)
8 oz/A; 32 oz/A/yr 7.7 oz/A; 46 oz/A/yr
Thiophanate-methyl 1 Topsin M WSB (UPI), others 1 lb/A; 3 lbs/A/yr Triphenyl tin hydroxide 30 Agri Tin (Nu Farm) Super Tin 80 WP (UPI)
Super Tin 4L (UPI) 7.5 oz/A; 45 oz/A/yr 12 oz/A; 72 oz/A/yr
Group FRAC Group #
Best Use Resistance Risk
Sterol Inhibitors or DMI’s
3 Budbreak/Pollination
Very High
Strobilurins 11 Budbreak/Pollination
Very High
Benzimidazoles 1 Pre-Pollination Very High
Tin Metal or TPTH
30 Post-Pollination Low-Moderate
Dodine 12 Post Pollination Low-Moderate
Phosphites 33 Tank Mix Moderate
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RESISTANCE MANAGEMENT
Ò Pecan Scab reproduces itself with great frequency during each growing cycle.
Ò Chemicals with narrow mode of action that are repeatedly exposed to the organism ultimately can become non-effective.
Ò Follow EPA Guidelines and restrictions on annual product use per acre---All Orchards!
Ò Rotate Fungicides Ò Spray with tank mixes with multiple modes of action Ò Use Products with Reduced risk of resistance.
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SIMPLIFIED EAST TEXAS PECAN SPRAY GUIDE Spray Timing Problems Materials
1 Budbreak Early April
Scab, Downy Spot Fungicide & Zinc + Nitrogen
2 14 days later April
Scab, Downy Spot Fungicide & Zinc + Nitrogen
3 14+ days later May
Scab, Downy Spot , Pecan Nut Casebearer
Fungicide & Zinc + Nitrogen + Insecticide
4 14-21 days later Late May, Early June
Scab Fungicide & Zinc + Nitrogen
5 14-21 days later Late June, Early July
Scab Fungicide & Zinc + Nitrogen
6 21+ days later Late July, Early August
Scab Fungicide
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SCAB CONTROL STOPS AT SHELL HARDENING
INFECTIONS AFTER SHELL HARDENING ARE NOT ECONOMICALLY IMPORTANT
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Stress
J. W. Stewart
Scab
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FUNGICIDES GENERALLY GIVE BEST RESULTS APPLIED WITH GROUND RIG THAT IS PROPERLY DESIGNED AND CALIBRATED
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BIG INVESTMENTS
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EFFECTIVE SPRAYER CONFIGURATION
65/75% of spray volume goes to upper 50% of canopy
35/25% of spray volume goes to lower 50% of canopy Pecan Volute: cowling that
channels half of air into more vertical orientation.
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WIND IS BAD
Ò Record wind conditions at time of spraying
Ò Ideal windspeed <5 mph Ò Reduced efficacy at 5-10
mph Ò Spraying should cease
>10 mph
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CALIBRATION FACTORS
Ò Spray Output: Gallons per minute of all nozzles. É Function of Pressure É Clean Screens & Filters É Proper Bypass Setting É Nozzle wear & corrosion
Ò Ground speed: Miles per hour (mph) Ò Tree Spacing and Trees/Acre
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ADJUSTING CALIBRATION
Ò To Increase GPT (Gallons per tree), reduce speed, increase pump pressure, use more nozzles or use larger nozzle tips (discs) and cores.
Ò To Decrease GPT, increase speed, decrease pump pressure, use fewer nozzles or use smaller discs and cores.
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EVALUATE COVERAGE