2018 ASHS Annual Conference

Within the organic fruit industry, peaches have experienced the largest increase in organic fruit acreage in the United States, but most of that acreage has increased in the west (Perez and Plattner, 2013). California, Washington, and Oregon currently supply the majority of domestic organic fresh market peaches (Hallberg, 2016). Peach producers in the southeast market fruit up to two months before west coast producers due to earlier warm temperatures and a later frost freeze damage potential. Producers select varieties that will set fruit when chill hour requirements are met (ranging from less to 100 to over 700), and can be harvested from late April through July to meet market demands.

Organic peach production in the southeast has been difficult due to the prevalence of insect and disease pests, as well as the lack of effective organically-approved pesticides (Horton et al, 2005; Blaauw et al., 2017). In addition, many of the compliant, commercially-available pesticides contain copper and other ingredients that may negatively impact soil health with overuse (NOSB, 2017). Organic fruit producers in the US, Spain, Japan and China have been installing paper bags to provide a physical barrier from both pests and pathogens and have been able to increase fruit quality and increase yield (Sharma et al., 2014), but bagging peaches in the US is an emerging approach. In a pilot study funded by the Southern IPM Center, J. Melgar, and G. Schnabel from Clemson University demonstrated that bagging peach fruit can reduce fruit damage from pests and diseases, increase yield, and increase quality with an estimated net cost of ten to fifteen cents a pound (Hallberg, 2016).

Pests and diseases can affect fruit quality throughout the entire growing season through postharvest. For example, the insect pests green stinkbug (Chinavia halaris (Say)) and plum curculio (Conotrachelus nenuphar (Herbst)) attack the fruit during initial development. Bacterial spot (Xanthomonas arboricola) is typically observed three weeks after petal fall, peach scab (Cladosporium carpophilum) is spread early in the season when the humidity and temperature are optimum for growth, and the most prevalent end of season and postharvest fungal diseases include brown rot (Monilinia fructicola) and rhizopus (Rhizopus nigricans).

To reduce pest-mediated damage, recyclable paper bags coated with a water resistant barrier are placed over fruitlets approximately ten days after full-bloom, when the when the fruitlet is approximately 1.5cm × 3cm, and removed approximately ten days before harvest to increase the blush color.