Reduction of Mycoflora and Control of In-Shell Weevils in Pecans Stored Under High Carbon Dioxide Atmospheres

Abstract

WELLS, J. M., and J. A. PAYNE. 1980. Reduction of mycoflora and control of in-shell weevils in pecans stored under high carbon dioxide atmospheres. Plant Disease 64:997-999. High carbon dioxide (C0 2) atmospheres reduced the mycoflora and controlled in-shell weevils in pecans stored under accelerated storage conditions of 7 C and 65% relative humidity. After 5 mo in atmospheres of 21% oxygen (02) and 30% CO2, pecan weevil mortality was 100%, total mycoflora isolated from kernels was significantly reduced, and off-flavors had not yet developed in the kernels. In atmospheres of 3 and 10% CO 2 (plus 21% 02) or in 1% 02 (with or without 30% CO2), weevil mortality was less than 100%. Objectionable off-flavors developed in high CO2 atmospheres after 6 mo. Alternaria and Pestalotia spp. were the fungi most frequently isolated from pecans held in air. After 5 mo in high CO2 atmospheres, Alternaria, Penicillium, and Fusarium spp. were the most frequently isolated fungi. In the southeastern United States, pecan (Carya illinoensis (Wang.) K. Koch) nuts are harvested from October to January. Much of the crop is refrigerated and stored to supply shelling plants with pecans throughout the year (11). In good crop years, refrigerated storage is an important means of holding excess supply until market conditions become more favorable to the producer. Since a heavy crop year is inevitably followed by a light crop year because of the alternate bearing nature of the pecan tree, longterm storage of pecans is also important in stabilizing the supply. Pecans are semiperishable. Highquality pecans may be held at 0-2 C for 1 yr before detectable off-flavors or rancidity develop (12). Not all pecans are of high quality at the beginning of storage, however. Late-harvested nuts may have lost freshness of flavor and the desirable light amber kernel color. Pecans may also be infested with the pecan weevil (Curculio caryae (Horn)), which damages kernels and provides avenues of invasion for postharvest storage fungi (9). Although refrigerated storage arrests the development of storage fungi and reduces damage caused by insects, it does not significantly affect survival of these organisms (5,8). Control is important, Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply approval to the exclusion of other products that also may be suitable.