Georgia Pecans: Fungicide Schedules – What to Spray and When

    Photo: Andrew Sawyer, Extension Agent, Thomas County, Georgia:

    Below you will find examples of effective fungicide spray programs. Because of the high variability in scab susceptibility from one variety to the next, this year’s suggestions will be a little more complex and based on the cultivar you grow and the level of scab pressure you have at an individual site.

    We have broken the cultivars down into 3 main categories (Low, Medium and High) as seen below. The 4th category–Medium/High — consists of cultivars that could fall into either of these 2 categories. Under most conditions they would have no scab problems under a regular spray program but in certain locations (below Highway 280, at low elevation, in crowded orchards) they will scab more and would need a high input program.

    Growers should use there own judgement and experience about where to place these. I am available to discuss this with any growers who are unsure about where their orchard fits.

    Low Medium Medium/High High
    Avalon Creek Caddo Byrd
    Elliot Kiowa Cape Fear Cunard
    Excel Oconee Huffman Desirable
    Kanza Sumner Schley Morrill
    Lakota Zinner Stuart Pawnee
    McMIllan Ellis Tanner Treadwell
    Gloria Grande Tom

    Low Input

    Low input cultivars are those with a very high degree of scab resistance –think Elliot, Excel, Lakota. These require a bare minimum of sprays–3 applications at most–primarily to help manage minor diseases aside from scab like powdery mildew, anthracnose, downy spot, etc. and to assist in maintaining scab resistance

    Spray 1:               Phosphite           ~ mid-late April

    Spray 2:               Phosphite           ~ mid-to-late May

    Spray 3:               11 + 3 mix           ~ early-mid June

    Medium Input

    These are cultivars that will require fungicide sprays to manage the disease but on which scab is usually easily managed without an intensive spray program in most locations. Some of these cultivars can fall into the high susceptibility category in locations with a history of scab on these particular cultivars or under situations of low elevation, poor air flow, or frequent rainfall. Use your best judgement with regard to where these cultivars fit for your own location.

    Scab on these cultivars should be controlled with 7 sprays. If excessive rainfall is occurring throughout the nut sizing period, you can shorten your interval and extend the program out further than 7 sprays by continuing to rotate Miravis Top and Elast/Tin in the example below.

    Spray 1:                              Phosphite                          ~ mid-late April

    Spray 2:                              Phosphite OR 11+3         ~ mid May

    Spray 3:                              Miravis Top                       ~ early-mid June

    Spray 4:                              Elast+Tin OR phosphite ~ mid-late June         

    Spray 5:                              Miravis Top                       ~ early-mid July

    Spray 6:                              Tin OR Elast+Tin               ~ mid-late July

    Spray 7:                              Miravis Top                       ~ early-mid August

    High Input

    These are cultivars that we know must be sprayed intensively in order to produce the crop. They will require at least 10 fungicide sprays and likely more in many locations. If you need to extend beyond spray 10, continue rotating Miravis Top and Elast/Tin. Bear in mind that some cultivars listed in the moderate category may fall into the high category in some locations.

    Spray 1:                              phosphite

    Spray 2:                              phosphite

    Spray 3:                              11 + 3 mix

    Spray 4:                              Miravis Top + phosphite

    Spray 5:                              Elast + Tin

    Spray 6:                              Miravis Top

    Spray 7:                              Elast + Tin

    Spray 8:                              Miravis Top

    Spray 9:                              Elast + Tin

    Spray 10:                            Miravis Top

    There are certainly more fungicides labeled for pecans than what you see listed in the examples above. Their exclusion from these examples does not mean they do not control scab. To the contrary, many are very good fungicides and could be rotated into a program just as easily as what you see above.

    But, based on Dr. Tim Brenneman’s data, we feel that these chemistries applied at the times shown above will offer maximum protection from leaf and nut scab. Group 3 and Group 11 fungicides are those containing both a Triazole and a Strobilurin fungicide chemistry (think Absolute, Stratego, Quadris Top, Amistar Top, Quilt, Brixen, Custodia, TopGuard EQ, and others)

    With the late foliage development this year, crop maturity could potentially be later than normal which means the need for these sprays in the medium to high input category could extend out beyond mid-August. Fungicide sprays should continue through shell hardening.

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