Cracking nut insect problems
Scientists from several UC Cooperative Extension offices, UC campuses, and the USDA San Joaquin Valley Agricultural Sciences Center are nearing the end of the first year of a five-year USDA grant to gain control of navel orangeworm in almonds, pistachios and walnuts in the Central Valley. By comparing traditional pest management practices to more environmentally friendly methods, researchers hope to improve monitoring and treatment for the moth over a wide range of conditions and nut varieties.
This collaborative effort is examining how harvest timing, orchard sanitation, mummy load (nuts that remain on the ground or in the trees after harvest), and navel orangeworm development influence the risk of pest damage when cultural controls and mating disruption are used to control this pest.
Navel orangeworm is a primary pest of several California tree crops, but especially nuts. When its eggs hatch, the larvae crawl around searching for a crack in the nut's hull to burrow into and feed on the kernel.
Scientists are conducting this study at test sites in Arbuckle, Colusa, Durham, Manteca, Sutter and Woodland. They are using standardized grower practices in some of the sites to validate an existing risk assessment model for navel orangeworm. For comparison, IPM Advisor Carolyn Pickel, UCCE, Sutter-Yuba counties, and Steve Welter, entomologist, UC Berkeley, monitor walnut and almond orchards for navel orangeworm using pheromone "puffers" and comparing them with orchards not using this method.
Puffers are aerosol cans that emit periodic "puffs" of pheromone, or the scent of navel orangeworm, in metered frequencies. Flooding an area with the scent makes it difficult for male navel orangeworms to find and mate with the females. The aerosol puffer units are hung high in the tree canopy and are designed to emit pheromone all season.
Orchard sanitation began in November. Pickel said, "Winter sanitation is the most critical component of the management strategy in almonds and walnuts. This involves shredding unharvested nuts to destroy them and stop the navel orangeworm from laying eggs in the nuts. In many years in Northern California, winter rain and wind, and sometimes birds, help growers destroy overwintered nuts. Growers need to count the mummies on trees in their orchards in winter and clean their trees if there are too many mummies. We advise an average of less than two mummy nuts per tree."
Entomologist Kent Daane from UC Berkeley is also involved in the research project and has begun to compare populations of the natural enemies of navel orangeworm in almond orchards with and without puffers. Natural enemies can be used to biologically control an insect pest.
Entomologist Joel Siegel from USDA Agricultural Research Service said his part in the project involves predicting insect damage in almond and pistachio orchards and whether destroying mummies on the ground, with pistachios in Kern County, is applicable to other regions in the state.
Later in the project, scientists will evaluate tree and ground mummies for navel orangeworm infestation. Before this project began, control efforts were focused on nuts that remained on the trees after harvest. Recent research indicates that nuts on the ground and in the trees must be considered as breeding grounds for the moth.
Scientists will compare their results with baseline data collected on the number of navel orangeworm, historic levels of damage, sanitation and the cost of current practices. They will then fine-tune the information to identify high-risk areas for the pest in all three nut crops.
Pickel said, "This is a unified effort among federal, state, local and private interests where we are involving participants in the program from conception to adoption. Our goal is to enhance grower profits, reduce worker risks and minimize environmental damage."
Participants are Pickel; Bob Beede, farm advisor, Kings County; entomologists Welter and Daane, UC Berkeley, and Frank Zalom, UC Davis; Karen Klonsky, agricultural economist, and Themis Michailides, plant pathologist, UC Davis. The USDA Agricultural Research Service is the lead agency with Joel Siegel, Chuck Burks, and L. P. S. "Bas" Kuenen. Bradley Higbee, Paramount Farming Company, is overseeing the project in Kern County.