Ask Your PCA: What are the best ways to control NOW?

Issue Date: April 8, 2020
Justin Nay PCA, Integral Ag Services, Durham
Justin Nay

Navel orangeworm is a major pest of pistachios and almonds. NOW started flying in February, and current pest pressure looks similar to 2015, when there were very high populations that started early in the season.

NOW was seen in pistachios the last week of February, and in almonds the first week of March. The drier, warmer weather has advanced the instar larvae. Some orchards are trapping large numbers, while others, particularly those with good sanitation, are clean.

Recommendations for managing NOW are, in this order: sanitation; mass trapping and/or mating disruption; spray applications and early harvest.

Sanitation is critical to controlling NOW. Removing the mummies from almond and pistachio orchards greatly reduces NOW populations, but sanitation efforts are directly linked to employee costs and availability.

Because of the earlier NOW arrival, mating disruption started in March this year, and first chemical treatments could be as early as mid-April unless there is a significant cool-down. If temperatures remain warm, the peak of the flight will arrive a couple weeks earlier than usual. Depending on the infestation levels, there could be two to three spray applications for NOW.

Growers currently have three treatments available for NOW. Resistance is always a concern with chemical applications, especially with limited options available.

Alternative harvest methods could help reduce NOW populations, depending on how they are implemented. If the nuts are harvested on the green side and then dried, that will break the NOW life cycle, but if they're harvested on the dry side, they will be harvested too late and NOW damage will continue.

Predator wasps, Copidosoma and Goniozus for NOW, have been found during mummy inspections. These parasitoids are working and killing NOW. Some orchards have more parasitoids than others, and organic orchards have the highest numbers, but they aren't being utilized by most growers at this time.

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.

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