Vol. 69 No: 6

Title:
Pollen Degeneration and Retarded Leaf Development from Fungicidal Sprays Applied During Microspore Development and Shoot Expansion

Authors:
YI HE and HAZEL Y. WETZSTEIN

pp: 975-984

Abstract:
Six fungicides: dodine (Syllit), propiconazole (Orbit), thiophanate-methyl (Topsin), fentin hydroxide (Du-Ter), benomyl (Benlate), and sulphur were applied in 1990 to field-grown ‘Desirable’ pecan (Carya illinoensis Wanganh C. Koch) trees from budbreak to pollen maturity. Pollen was collected and germinated on pesticide-free media. Dodine (sprayed once weekly) and propiconazole, sulphur, thiophanate-methyl, and benomyl (sprayed once and thrice weekly) reduced pollen germination compared with controls. Fentin hydroxide caused the least inhibition, and reduced germination only in thrice weekly sprays. Applications were repeated in 1991 with the three fungicides (dodine, propiconazole and sulphur) which most severely reduced pollen germination in 1990. In once weekly sprays, inhibition with dodine was only 21% compared with 61% observed in 1990; propiconazole and sulphur showed no difference from controls. Possible seasonal weather effects are discussed. Propiconazole was the only fungicide to suppress catkin and leaf growth. Fungicides applied during early season growth may contribute to aberrant microspore development, pollen degeneration and retarded development of catkins and leaves.

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