Controlling Scab in a Tough Year. Bill Goff Department of Horticulture Auburn University

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1 Controlling Scab in a Tough Year Bill Goff Department of Horticulture Auburn University

2 First let s state the obvious Pecan scab, a fungus disease, is much worse, like most fungus diseases, under wet conditions. It s been a very wet year in the Southeast!

3 Why Scab is so bad this year One of the wettest summers in years Yearly average rainfall for GCREC = inches Rainfall to date = inches Rainfall in scab susceptible months May June July August Normal for May-August Total for May-August B. Wilkins

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5 It s all about the weather!

6 Nut Scab (Late Aug) Scab Severity on Wichita, Tifton, GA (Trt = 10 sprays of Elast/TPTH) In 2002, a dry year, 10 sprays on Wichita resulted in very good control in Tifton, GA * * 2004 used Elast/Enable Treated Nontrt Source: Tim Brenneman

7 Nut Scab (Late Aug) Scab Severity on Wichita, Tifton, GA (Trt = 10 sprays of Elast/TPTH) In 2003, a very wet year, the same 10 sprays resulted * in very poor control. * 2004 used Elast/Enable Treated Nontrt Source: Tim Brenneman

8 Observations from growers who successfully controlled scab in Numerous phone calls to growers, researchers, extension specialists, and scouts were made to find out who controlled scab and how they did it. Site visits were made to research stations and to orchards in Alabama, Georgia, and Mississippi. Responses and observations were summarized for this report.

9 Steps followed by growers who successfully controlled scab on susceptible cultivars in They sprayed early, they sprayed late, and they sprayed often, greatly adjusting their normal spray schedule to match the conditions.

10 Effect of Delayed Sprays on Nut Scab (Desirable, 2003) Shell Hardening Severity (%) * * * * * 6/1 7/1 8/1 9/1 10/1 1 thru 9 2 thru 9 3 thru 9 4 thru 9 Nontrt * = Fungicide spray

11 Effect of Early-Terminated Sprays on Nut Scab (Desirable, 2003) Shell Hardening Severity (%) * * * * * 6/1 7/1 8/1 9/1 10/1 1 thru 9 1 thru 8 1 thru 7 1 thru 6 Nontrt * = Fungicide spray

12 Steps followed by growers who successfully controlled scab on susceptible cultivars in They strived for good coverage. They slowed the sprayers to 1 ½ to 2 mph. They often sprayed at night, when wind was less, and to allow the spray to dry before the frequent afternoon rains. Many supplemented with aerial applications. All sprayed 100 gallons per acre. Some hedged, or removed lower limbs from tree.

13 Water sensitive cards used to detect spray coverage. Problems: 1. Does not measure biological activity of the pesticide. 2. Difficult to handle and place the cards. Other Methods: 1. Water sensitive strings over the canopy. 2. Disease ratings. Problems: 1. Does not measure biological activity. C. Reilly 2. Dependant on weather conditions.

14 Steps followed by growers who successfully controlled scab on susceptible cultivars in They used many different fungicides. Often more than one fungicide was in the mix, usually at full rates of both. Elast and Quadris Top were components of mix for nut scab control.

15 Example spray program on Desirable in /8 Prophyt---2 qts 4/17 Super Tin 6.4 oz+elast 25 oz 5/2 Absolute 5 oz+tebuzol 3 oz 5/8 Absolute 5 oz+tebuzol 3 oz 5/13 Absolute 5oz+Tebuzol 3oz 5/20 Prophyt 2qt 6/4 Prophyt 2 qts+super Tin 12.8 oz 6/13 Super Tin 9.6 oz+elast 38 oz 6/25 Super Tin 9.6 oz+elast 38 oz 7/2 Quadris Top 11oz+Prophyt 1.5 qts 7/9 Super Tin 9.6 oz+elast 50oz 7/15 Quadris Top 11oz+Prophyt 1.5 qts 7/23 Super Tin 6.4 oz+elast 50oz 7/29 Super Tin 12 oz+topsin 20 oz 8/5 Elast 50 oz+topsin 20 oz 8/12 Super Tin 12 oz 16 fungicide sprays through Aug 12, over 20 sprays total Cost: $287.90/acre* L. Wells

16 33 Southeastern orchards were sampled in 2008 and scab was evaluated for fungicide sensitivity Compared to the non-treated orchards, significant reductions in sensitivity were detected in 20 orchards to fentin hydroxide, in 4 orchards to dodine, in 6 orchards to thiophanatemethyl and in 20 orchards to propiconazole. Seyran et al. 2010

17 Representative scab on Desirable in 2013 at orchard near Ray City, GA managed by Jeff Dorsey. Photo by J. Brock

18 Practices Jeff Dorsey followed in fungicide sprays, 18 ground sprays and 1 aerial spray. Intervals were about 7 days in rainiest periods. Full rates always. Tank mixes were full rates of all products used. Example: Spray guide rate for Absolute is 5 oz, but label allows 7.67 oz. Jeff used Speed was 2.0 mph. Used many different fungicides, often full rate mixes of both, including Absolute, Tin, Elast, some phosphites. He used a Durand Wayland 3210 sprayer, spraying both sides. On 2 other less powerful sprayers, he sprayed one side only.

19 What Jeff Dorsey did that was novel and different He usually used Speed, a silicone surfactant, in combination with fungicides. At first, didn t use with Elast for fear of leaf burn, later did use, even with Elast. He feels this may have improved his coverage.

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21 Modified by Bill Goff from Jim Dutcher s work and used out of context without permission.

22 Comparison of spray pattern in pecan trees sprayed with two treatments Level in Canopy top middle bottom 100 gal/acre + surfactant 100 gal/acre Drops per square cm

23 = 100 gals per acre

24 What Jeff Dorsey did that was novel and different He used two sprayers, synchronized and spraying in tandem on the same tree at the same time. He sprayed North-South, with 2 sprayers spraying the same tree at the same time, then 7 days later he sprayed east-west with 2 sprayers spraying at he same time.

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26 Do we really want to live like this? Let s shift to scabresistant cultivars. Ellis 0 fungicide sprays in 2012 Sumner Worst Typical Best

27 Ellis 44 nuts/pound 57 % kernel Good scab resistance. Oct. 12 harvest date, 3 days or so before Desirable. Good scab resistance, similar to Sumner. Good and consistent yields Excellent export and giftpack marketing potential. Patented by Elliott Ellis.

28 Table 1. Pecan cultivar recommendations for Southeastern orchards, grouped by scab resistance. Recommended Recommended Scab conditionally for home plantings resistance level Recommended or for trial only Excellent Excel Kanza Amling Gafford Adams 5 Headquarters Prilop Miss L Good Ellis Sumner Baby B Eclipse Elliott McMillan Mediocre Caddo Creek Apalachee Mandan Giftpack Poor Pawnee Desirable alabamapecangrowers.com