California Agriculture

The navel orangeworm (NOW), a primary pest of almonds and pistachios in California, is controlled in part by sanitation, with a current threshold of two mummy nuts or fewer per tree. However, almond and pistachio acreage has increased dramatically since the tree mummy threshold was established. This study addresses the impact of this expansion and the possible need for a more stringent standard. Beginning in 2002, the Paramount Farming Company conducted a series of large-scale studies reevaluating the current tree mummy threshold in almond orchards, as well as the impact of ground mummies and proximity to pistachio orchards. The data supports a more stringent threshold of 0.2 mummies per tree. In addition, a new threshold for ground mummies of four per tree for ‘Nonpareil’ almonds is supported in Kern County, although this needs to be validated in other regions. Proximity to pistachios was an important risk factor for navel orangeworm damage of 2% or less in almonds. Likewise, the influence of pistachios extended 3 miles from the center of the 10-acre almond orchard sections in our experiments to the margin of the nearest pistachio orchard.