Submitted to: California Pistachio Commission Production Research Report
Publication Type: Proceedings
Publication Acceptance Date: 7/13/2004
Publication Date: 7/13/2004
Citation: Siegel, J.P., Noble, P.M., Lacey, L.A., Bentley, W., Higbee, B.S. 2004. Use of nematodes for post harvest control of navel orangeworm (amyelois transitella) in fallen pistachios. California Pistachio Commission Production Research Reports. 287-293. Interpretive Summary: The ability of two species of insect pathogenic nematodes to kill navel orangeworm (Amyelois transitella) in fallen pistachios was investigated using a series of small plot studies. Infested nuts were placed on the ground and sprayed with concentrations of nematodes ranging between 50,000 and one million infective juveniles (IJs) per square meter. The application rate of water used was 374 or 500 ml, corresponding to 400-534 gallons per acre. One species of nematode, Steinernema carpocapsae, was more effective and killed more than 72% of the target larvae when applied at a concentration of 100,000 IJs per square meter. Nighttime temperatures below freezing were deleterious. Nematodes successfully attacked navel orangeworm larvae even when the nuts were covered with fallen leaves, and the nematodes multiplied in the larvae that they killed. These trials demonstrated that further research on the efficacy of S. carpocapsae is warranted.
Technical Abstract: Four trials employing one square meter plots were conducted between February and July 2003 in Madera County, California to evaluate the ability of two species of nematodes, Steinernema carpocapsae and Steinernema feltiae to control navel orangeworm, Amyelois transitella, in infested pistachios on the ground. The plots were located in two 16.2 hectare blocks of pistachio trees planted in sandy loam soil. A total of 3,095 larvae were recovered from 18,390 laboratory-infested pistachios (16.8% average infestation). Nematodes were applied with a backpack sprayer at concentrations ranging form 50,000-1,000,000 infective juveniles (IJs) per square meter and an application rate of 374 or 500 ml water per square meter (400-534 gallons per acre). S. carpocapsae was more effective than S. feltiae in pistachios and produced > 72% mortality at a concentration of 100,000 IJs per square meter when nighttime temperatures were above freezing. S. carpocapsae was equally effective in bare and leaf-covered plots and persisted longer in sandier soil (8 weeks) than S. feltiae. S. carpocapsae has the potential to multiply in the field; 51.3% of the cadavers examined 21 days after application contained nematodes (n =226). Our trials demonstrated that S. carpocapsae can play a role in the post harvest control of navel orangeworm and that the formulation tested produced greater mortality than the formulation of S. feltiae tested at the same concentration.