mar-apr-2020

THE ALMOND BOARD Navel Orangeworm Monitoring Starts Now Almond growers know that the fight against Navel Orangeworm (NOW) is a year-round effort — they’re never “off the clock.” That’s because NOW remains one of the biggest threats to a grower’s crop — and bottom line — due to the damage worms can do to nuts and the risk of aflatoxin contamination. Growers’ battle against NOW takes different forms during different times of year. In the winter, the focus is on ridding orchards of mummy nuts, the cold-weather hideouts for NOW larvae. During the beginning of nut set, the fight transitions to locating and eradicating as much of the first generation, or “flight,” of moths that spur the exponential growth of future NOW generations each season. Use Traps to Track NOW Levels Pest management experts say the primary thing growers should be doing this time of year to combat NOW is to put out pheromone and egg traps to help determine NOW levels in their orchards. Pheromone traps monitor the flight of male moths. It is recommended that growers hang one trap per 50 acres, or at least two per orchard, in the tree canopies about six to eight feet off the ground. The best time to place traps is in early March. The University of California (UC) Integrated Pest Management (IPM) guidelines advise growers to “count the number of moths in the trap at least once per week and track the data to identify adult flight.” It is also important to correctly identify NOW moths, which are characterized by their “irregular, silver gray and black forewings and legs and a snoutlike projection at the front of the head,” as pheromone traps also attract meal moths, which are light brown with dark brown bands on their wings. In terms of egg traps, UC IPM guidelines recommend that growers place these traps in their orchards by March 15. It is suggested that there be at least one trap for every 10 acres, or a minimum of four traps per orchard. More traps — as many as 10 per orchard — allow for a more accurate estimate, experts say. Egg traps are made up of black plastic tubes with mesh siding and snap tops, and are half- to three-quarters full of almond presscake laced with three to 10 percent almond oil. Growers can also grind almond or pistachio mummy nuts to use instead of presscake. Traps should be monitored for NOW larvae eggs one to two times a week, and are most effective during the first flight of NOW in April and May. The UC IPM website offers a monitoring form 1 growers can use to help keep track of the number of eggs per trap during the monitoring period. Using traps to determine NOW levels and choosing the appropriate treatment option is an important part of every grower’s IPM program. Growers can consult the UC IPM website 2 for treatment options, in addition to speak with their PCAs. March is the time when the fight against Navel Orangeworm moves from winter sanitation to setting traps in orchards. IN YOUR ORCHARD 3 0 A L M O N D F A C T S