L The Influence of Powdery S U Mildew on Pecan Nut Quality A g C Charles J. Graham e n Pecan Research/Extension Station t e r
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Pecan Scab L S U A g C e n t e r
Several diseases at same time. L S U A g C e n t e r
L S U A STUART g C PECAN e n t e r
L POWDERY S U MILDEW A g C e n t e r
Powdery Mildew L The fungus Microsphaera penicillata (Wallr.:Fr.) Lev S causes powdery mildew of pecan. U On pecan, powdery mildew primarily appears A g mid‐to‐late season and will generally only affect C fruit, but can be found on leaflets occasionally. e n Powdery mildew can occur sporadically and may t not be present each year . e r
Powdery Mildew Gottwald et al. (1984) found that powdery L mildew had no effect on net photosynthesis or S dark respiration of nuts, but 50% coverage on U the shuck reduced kernel oil, protein, and free A fatty acids. g C e n t e r
Powdery Mildew Brenneman and Bertrand (1989) reported that L disease levels were significantly negatively S correlated with kernel weight, but the percent U fill of nuts were not correlated with disease A severity. g C e n t e r
Powdery Mildew Olsen et al. (2003) reported no significant L differences in nut weight, kernel weight, S percent fill, or kernel color ratings on infected U and non- infected ‘Wichita’ and ‘Western’ pecan A varieties. g C e n t e r
Pecan Cultivars Susceptible to Powdery Mildew • Curtis L S • Desirable U • Farley • Moore A g • Pabst C • Wichita e • Western n t e r
Initial infection L S U A g C e n t e r
Advanced infection L S U A g C e n t e r
L SHUCK S U DECLINE A g C e n t e r
Shuck Decline Stem-end Shuck Dieback Blight L Tulip Disease S U A g C e n t e r
Pecan Cultivars Most Susceptible to Shuck Decline • Success L S • Desirable U • Forkert • Choctaw A g • Pawnee C • Oconee e • Creek n t e r
L TEST S U CONDITIONS A g C e n t e r
Orchard Description Orchard planted in 2005. L S U Six cultivars: Caddo, Desirable, Elliott, Nacono, Oconee, Pawnee A g C Only 4 fungicide applications: e n Prophyte, Elast, Super Tin, Agri-fos t e r
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Data Collection 25 random nuts of uninfected, powdery mildew infected, and with L shuck decline symptoms collected S from each individual tree. U A Four replicant trees for each cultivar. g C e n Individual nut length, nut diameter, t nut weight, kernel weight, oil content. e r
L S U RESULTS A g C e n t e r
Desirable L S U A g C e n t e r
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‘Desirable’ Pecan TRT Length Width L S U Control 44.27 a 24.22 a A g P. Mildew 42.92 b 23.84 a C e n Shuck Decline 42.95 b 23.91 a t e r
‘Desirable’ Pecan TRT Nut Kernel Percent Weight Weight Kernel L S Control 10.29 a 5.48 a 53.17 b U A P. Mildew 9.47 b 5.20 b 54.85 a g C Shuck Decline 9.67 b 5.26 ab 54.32 ab e n t e r
‘Desirable’ Pecan TRT Nuts/lb % Oil L S U Control 44 a 67 a A g P. Mildew 48 b 64 a C e n Shuck Decline 47 b 62 a t e r
Oconee L S U A g C e n t e r
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‘Oconee’ Pecan TRT Length Width L S U Control 48.74 a 22.54 a A g P. Mildew 48.08 a 22.21 b C e n Shuck Decline 47.20 a 22.09 b t e r
‘Oconee’ Pecan TRT Nut Kernel Percent Weight Weight Kernel L S Control 9.79 a 5.69 a 57.83 a U A P. Mildew 9.12 b 5.32 b 58.02 a g C Shuck Decline 8.67 b 4.98 b 57.23 a e n t e r
‘Oconee’ Pecan TRT Nuts/lb % Oil L S U Control 46 a 71 a A g P. Mildew 50 b 72 a C e n Shuck Decline 52 b 70 a t e r
Pawnee L S U A g C e n t e r
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‘Pawnee’ Pecan TRT Length Width L S U Control 47.22 a 23.90 a A g P. Mildew 45.44 a 23.43 a C e n Shuck Decline 46.15 a 23.60 a t e r
‘Pawnee’ Pecan TRT Nut Kernel Percent Weight Weight Kernel L S Control 9.29 a 5.50 a 59.29 a U A P. Mildew 8.76 a 5.32 a 60.84 a g C Shuck Dieback 9.03 a 5.40 a 59.74 a e n t e r
‘Pawnee’ Pecan TRT Nuts/lb % Oil L S U Control 49 a 74 a A g P. Mildew 52 a 74 a C e n Shuck Decline 50 a 74 a t e r
L PECAN CULTIVAR S U SUSCEPTIBILTY A g C e n t e r
Powdery Mildew T olerant Susceptible Highly L Susceptible S • Jackson • Caddo • Curtis U • Littlepage • Gloria Grande • Desirable • Maramec • Kiowa • Forkert A g • Pawnee • Moreland • Melrose C • P-Cou 2 • Nacono e • Sumner • Oconee n • Schley t e r
Powdery Mildew Many growers regularly spraying for scab L are surprised to see powdery mildew S development on their nuts. U A Many of the fungicides that are effective g for scab are not effective in controlling C powdery mildew. e n t e r
Fungicides Labeled L • Group 30, organotin S • Group 3, DMI’s U • Group M, guinidine acetate A • Group 11, strobilurin g • Group 1, thiophanate-methyl C • Group 33, phosphonates e • Group 6, G3 & G11 Mixtures n t e r
Fungicides Labeled L • Agri-Tin, Super Tin 4L, Super Tin 80WP S U • Enable, Orbit, Propimax, Bumper • Elast 400F A • Abound, Sovran, Headline g • T Methyl 70 WSB, Topsin-M C • Agri-fos, Fosphite, ProPhyte, Rampart e • Stratego, Quilt n t e r
Fungicides Labeled L • Agri-Tin, Super Tin 4L, Super Tin 80WP S U • Enable, Orbit, Propimax, Bumper • Elast 400F A • Abound, Sovran, Headline g • T Methyl 70 WSB, Topsin-M C • Agri-fos, Fosphite, ProPhyte, Rampart e • Stratego, Quilt n t e r
L S U SUMMARY A g C e n t e r
Powdery Mildew Desirable Pecan – significantly reduced nut length, nut weight, kernel weight, nuts/lb, L and oil content. S U Oconee Pecan – significantly reduced nut diameter, nut weight, kernel weight, and A nuts/lb. g C e Pawnee Pecan – severe infection of n powdery mildew had no significant effect t on any of the measured quality e parameters. r
Summary Powdery Mildew infection is sporadic in L S occurrence and not considered a significant U economic problem, therefore specific fungicide application for powdery mildew A control is not recommended. g C e Fungicide choice for pecan scab control will n impact powdery mildew infection. t e r
L S U QUESTIONS?? A g C e n t e r
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