First Report of Septoria Leaf Spot of Pistachio in New Mexico

Abstract

In September of 2008, a Septoria sp., the causal agent of Septoria leaf spot of pistachio (Pistacia vera L.) was isolated from leaf lesions in an orchard in southern New Mexico. Tree fruit and nut crops including pistachios are becoming an increasingly important part of New Mexico's agricultural industry with total cash receipts of $103 million in 2007 (3). This preliminary positive for Septoria prompted a survey of pistachio-growing counties in the state. The surveyed orchards accounted for approximately 30% of the pistachio acreage in New Mexico. Results indicated that all five pistachio-growing counties had orchards infected with a Septoria sp. Isolates of Septoria from leaf lesions were identified as Septoria pistaciarum Caracc. based on the following symptoms and morphological characteristics of the fungus: leaf lesions were usually circular, 0.5 to 3 mm in diameter, and contained many pycnidia per lesion; pycnidia were dark, ostiolate, and measured 101 to 255 × 69 to 133 μm; and conidia were hyaline, filiform, contained 3 to 9 septa, and measured 3 to 4 × 60 to 149 μm. Most orchards were only mildly affected. In severe cases, hundreds of leaf lesions were present on diseased leaves; large sections of the leaves turned tan and some trees defoliated prematurely. This widespread occurrence of Septoria leaf spot in New Mexico in 2008 suggests that the disease had already been present in the state for several years. A higher average rainfall in the summer of 2008 provided excellent conditions for disease development. Because of the high amounts of inoculum currently present in New Mexico orchards, Septoria leaf spot may emerge as a recurring disease problem for pistachio producers. This disease was first reported in the United States in Texas in 1971 and was also reported in Arizona in 1989 (1,2,4). To our knowledge, this is the first report of Septoria leaf spot of pistachio in New Mexico. References: (1) A. Chitzandis. Ann. Inst. Phytopathol. Benaki 10:29, 1956. (2) J. L. Maas et al. Plant Dis. Rep. 55:72, 1971. (3) New Mexico Agricultural Statistics, Department of Agriculture, 2007. (4) D. J. Young and T. Michailides. Plant Dis. 73:775, 1989.

Septoria (Septoria pistaciae Desm.) pathogen infecting pistachio nuts in Uzbekistan and its biological characteristics

“…A number of authors have pointed out that septoria disease of pistachio plant occurs in all pistachio fields. Under the influence of the disease, not only the yield, but also the quality of the plant decreases [1]. The fungus Septoria histaciarum, which causes the disease on the leaves of the pistachio plant, was identified in Arizona, USA [2].…”

“…Septoria sp. fungus was isolated from infected leaf of pistachio for the first time in the southern New Mexico (USA) in 2008 [1]. This fungus was isolated from all pistachio orchards in the area and identified as S. histaciarum.…”