Navel Orangeworm Pressure Could Be Increasing in Almonds

Lack of Good Sanitation Leads to High Navel Orangeworm Numbers

By Jessica Theisman, Associate Editor

It could be another heavy year for Navel Orangeworm (NOW). David Haviland, UC Cooperative Extension farm advisor for Kern County and entomologist told California Ag Today that sanitation in almond orchards over the winter was not as good as it could have been.

“Everything right now is about trying to prevent a repeat from last year, and it is a little tricky so we know that sanitation wasn’t as good this winter as it generally should be,” he said. “The best time to shake NOW mummy nuts from an almond tree is after a rain when the nuts are heavier.”

David Haviland on Pyrethroid Review
David Haviland

However, rains came late this season, and by the time the rains left, there was only a few weeks before spring.

“This left a very short window to get any shaking done, and some people did an excellent job during that window to sanitize and other people just couldn’t get around all their acreage,” Haviland said. “On average across the whole industry, sanitation was not up to where it should have been, and it gave growers a difficult start to the season.”

NOW could be early this year, but the crop is on time.

“With all of this prolonged hot temperatures, particularly high night-time temperatures, the trees are shutting down a little bit at night compared to what they would do if the nighttime temperatures were cooler,” Haviland explained.

As a result, harvest is not coming as quickly as people would like.

“The problem is that the longer the nuts are in the orchard, the greater chance there will be NOW damage,” he said.

Timely crop protection sprays are recommended.

Almond and Pistachio NOW Sanitation Critical This Winter

Joel Siegel on NOW Sanitation

By Patrick Cavanaugh, Farm News Director

Last year was a bad year for navel orangeworm (NOW) mainly in pistachios, but also in almonds. If left in the trees, infested nuts become a great reservoir for more NOW to inhabit them.

Joel Siegel, NOW research entomologist, USDA Agricultural Research Service
Joel Siegel, research entomologist, USDA Agricultural Research Service

Joel Siegel, a research entomologist for the USDA Agricultural Research Service based in Parlier, stresses the importance of having a good sanitation plan in place to remove those NOW mummy nuts. “When we talk about sanitation, it should be the foundation for everyone’s nut program. That’s something that you control.”

“In almonds, it’s absolutely essential. Where we’ve taken a look at it in the south, every infected mummy per tree is good for 1 percent damage. So going from one mummy to two mummies, your damage on average increases another 1 percent.”

“It’s also important to destroy the mummies on the ground. You figure, for every eight or nine mummies on the ground, that’s good for about a half a percent increase in damage. Get them off the tree and shred the almonds.”

Siegel noted that while pistachio growers can clear mummy nuts off the tree, the industry has not been able to shred the fallen pistachios effectively. The hard, rounded pistachio shells just bounce around in the shredder machine.

almond_mummies
Almond Mummies

“What you can do is shake them off the tree as soon as possible so they’re on the ground where they can start rotting. You get those weeds growing around them. It has been shown that they break down faster in the weeds,” said Siegel.

“Growers disc them in. But if you’re going to disc them in, you have to disc them twice. Again, you’re not destroying the nuts, you are burying them so that NOW cannot lay eggs in the spring,” he said.

The risk of poor sanitation is high. Considerable NOW damage can prevent pistachio and almond growers from earning the premium paid for nuts that are pest-free.