Pecan Tree Dieback Following 1999-2002 Drought Associated with September Rainfall

Abstract

During spring 2002, after three years of drought, tree dieback occurred on pecans [ Carya illinoinensis(Wangeh.) C. Koch] in Georgia. Dieback severity varied by location within the state. Dieback was visually rated in mid-May 2002 as none, mild, or severe. Degree of dieback was compared with the sum of rainfall departures from normal for 1999 to March 2002. Rainfall departures were calculated by location on an annual basis, for the dormancy period, and individually for progressive stages of tree and fruit development. Dieback was correlated only with rainfall departures occurring during the period of kernel filling. During kernel filling, rainfall was 307 mm above normal in the area with no dieback, 124 to 200 mm above normal in areas with mild dieback, and near normal in areas with severe dieback. These data suggest that effects of severe drought can be greatly negated if rainfall is substantially above normal during kernel filling. These data also suggest that irrigation during the stress of kernel filling may be especially critical and if irrigation allocations become restricted in the southeastern United States, irrigation during kernel filling may produce greater profits and better tree vigor than at any other single time of the year.