RELATIVE SUSCEPTIBILITY OF PECAN CULTIVARS TO ZONATE LEAF-SPOT

Zonate leaf spot (ZLS) [Cristulariella moricola (Hino) Redhead (C. pyr amidalis Waterman and Marshall)] on pecan [Carya illinoinensis (Wangen h.) K. Koch.]-associated with unusually wet weather during June, July, and August-occurred across much of Georgia during Summer 1994. Scott- Knott cluster analysis indicated that 27 of 36 evaluated genotypes exh ibited little or no field susceptibility to ZLS. 'Moneymaker' exhibite d the greatest susceptibility of all cultivars studied, with 'Cape Fea r', 'Elliott', 'Sumner', and 'Sioux'' segregating to exhibit moderate susceptibility, An evaluation of commercial orchards indicated suscept ibility of major southeastern cultivars as 'Desirable' < 'Stuart' < 'S chley' < 'Moneymaker'. Control of ZLS in commercial orchards using sta ndard fungicide spray strategies appeared to be generally ineffective.