Fungicidal suppression of peach leaf rust in low-chill subtropical grown peaches

Robert E. Rouse, Pamela D. Roberts


Low-chill subtropical peach (Prunus persica L. Batsch) varieties with chilling requirements below 250 chill units and commercial quality have been developed in the University of Florida peach breeding program. Low-chill varieties have been successfully fruited in central and south Florida and have commercial production potential. One limitation may be the control of peach leaf rust (Tranzschelia discoloi) which causes premature leaf loss in late summer during the rainy season which favors disease development, applications of azoxystrobin (Abound, 0.15 Ib ai/A), chlorothalonil (Bravo Weather Stik, 1.06 Ib ai/A) or mycobutanil (Nova 40W, 2.4 lbs ai/ A) were made at 3 or 6-week intervals to trees that were center pruned or unpruned. Disease severity of rust lesions was assessed at 21 day intervals from August to November 1999. Disease was significantly reduced by applications of mycobutanilat 3 weeks to pruned trees and at 6 weeks to trees pruned or not pruned compared to either control. Disease on trees treated with azoxystrobin were significantly reduced compared to the unpruned control and lower compared to pruned control. Applications of chlorothalonil did not significantly reduce the disease. Trial results show that azoxystrobin and mycobutanil were effective against peach leaf rust and may be instrumental in producing peaches that ripen fruit in a market window when no other peaches are available in April and early May.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283