Almond growers are reporting some significant damage caused by navel orangeworm (NOW) this year. The increased presence of the pest is partially due to weather conditions complicating management efforts. UC Cooperative Extension Pomology Advisor for Merced County David Doll believes that “a lot of this has to do with the lack of access we’ve had into these orchards in regards to winter sanitation.”
Doll also noted that some growers may have been too relaxed in their attitudes toward NOW and are not fully appreciating the importance of winter sanitation in orchards.
Sanitation is one of two strategies to lower overwintering populations but remains the primary method. NOW overwinters within the mummy and Doll explained, “that’s why getting them out of the tree and onto the ground can help reduce populations.” Getting mummies onto the ground and shredding them eliminates the only food source available to the pest, reducing their overall numbers.
Another issue relates to the reports coming from processors regarding the percent of NOW damage. When growers get the report back from processors indicating some degree of NOW damage, Doll noted that their comparison data is showing at least double those levels in the field. “So, if you’re getting a two percent navel orangeworm damage report from the processor, that usually means you’re getting four percent loss in the field,” Doll stated.
There are a few different reasons for the difference in reported damage and actual loss. One cause is because some of the damaged nuts are lost in the harvesting process itself and not included in what arrives at the processor. The other reason stems from processors determining damage based on weight and not count. “When you’re weighing nuts that have been half-eaten it is less damage than if you did a true nut count of ones that have been infested,” said Doll.
Doll recommended keeping the difference of actual loss and reported damage in mind when crafting management strategies. When a processor presents a grower with a damage report showing what kind of problem NOW is for their operation, Doll stressed that growers “have a bigger problem than they think they have.”
Listen Doll’s interview.
09-11-17 Doll NOW