Electronic repeller and field protocol for control of crows in almonds in California

Past studies have shown that the American crow, a major pest in almonds, can be effectively hazed out of almond orchards with broadcast distress calls. These studies, however, have not approached the matter from an integrated pest management standpoint. A large-scale field protocol was required to guide growers when using electronic broadcast units. A broadcast unit was designed for testing the field protocol with emphasis placed on preventing habituation and saving power. A selection of crow chick distress calls were recorded on the University of California-Davis campus for use in the broadcast unit. In addition, recordings of 2 dying adult crows were obtained from the United States Department of Agriculture National Wildlife Research Center in Fort Collins, CO. The calls proved effective in preliminary hazing tests and during the field study. The field protocol included broadcast unit deployment at the first sign of bird damage at a rate of one unit per 1.6 ha, distributed uniformly throughout the orchard, moved to a new tree every 2 weeks, and automatically switched to a different call every 3 to 4 days. Growers at each site were also supplied with pyrotechnics to supplement the distress calls and were encouraged to use other techniques such as shooting and gas cannons. The units ran until harvest. Six orchards, a pair from each of 3 different areas in California, were chosen to test the field protocol. The orchards were surveyed for damage over 2 growing seasons, and 1 orchard in each pair received treatment in the second year. Two of the 3 treated sites showed a decrease in damage due to the treatment of the broadcast units implemented with the field protocol. One site showed a damage reduction from 0.84 (6.0 kg/ha) to 0.25 (1.1 kg/ha). Another site showed a damage reduction from 1.54 (18.2 kg/ha) to 0.73 (4.8 kg/ha). The third site was not damaged in the first year, therefore damage reduction in the second year was not possible