Pear fruit is an important crop in California, accounting for over 20,000 acres of orchards in 1999. The codling moth is a significant pest in the production of pear fruit, and can cause damage in up to 10-50% of cannery loads when orchards are untreated. A series of conventional pesticides were severely restricted and subsequently phased out between 1998 and 2000, generating incentives to develop more benign alternatives. Azinphos-methyl was the most effective tool for controlling codling moths prior to 1998. Its use was first restricted by the state of California in 1998 and further restricted by the US EPA in 1999. Another pesticide used, methyl parathion, was eliminated in 2000 under the Food Quality Protection Act. These regulatory changes necessitated an immediate transition to alternative pest management strategies for codling moth on pears (UC ANR, 1999).
Extensive research and development has been conducted on two biopesticide alternatives that can be used alone or in conjunction with one another to control codling moths. The first is a pheromone used in mating disruption and the second is a granulosis virus (GV) that infects codling moth larvae. An early technological challenge to develop a reasonably priced pheromone dispenser was overcome by a researcher at the University of California with funding from the pear industry. Product development and field-testing later transitioned to Suterra, a manufacturer of pheromones for pest management.
Rachel Elkins, the Pomology Farm Advisor at the University of California Cooperative Extension, performed field-testing for GV. The funding for her research came from a federal IR-4 grant. She focused on efficacy testing, comparing different treatment conditions and types of applications. She found that a narrow set of conditions resulted in acceptable efficacy, posing challenges to growers. The virus must be ingested by the codling moth at a particular stage early in its life cycle, prior to burrowing into the fruit. The virus is also sensitive to various weather conditions such as being washed off by rain or degraded in sunlight. With these constraints, application timing and knowledge and detection of the pests are critical for success. Due to its short life, GV may require multiple applications, adding labor and fuel costs for growers. To be most effective, GV is typically used in combination with mating disruption or another type of pest management strategy.
This example highlights how regulatory changes can create strong drivers for the technical innovation and grower education required to transition to more benign pesticide alternatives. It also emphasizes that shifting to more sustainable agricultural practices rarely is as simple as a one to one replacement of an existing pesticide, and requires a paradigm shift to holistic system-based approaches to agriculture and pest management. Information and education are keys to the success of these alternatives.