Navel Orangeworm Control Critical

Orchard Sanitation is Critical This Season To Lower NOW Numbers

By Patrick Cavanaugh, Farm News Director

Emily Symmes is the area Integrated Pest Management farm advisor for the Sacramento Valley in the statewide IPM program. She recently spoke to California Ag Today about the high level of Navel Orangeworm (NOW) damage in nut orchards throughout California this past season.

“We had a lot of unique circumstances. The amount of rainfall we got in late 2016 into 2017 was pretty unprecedented and really led us into a really bad navel orangeworm year because we couldn’t get out and sanitize our nut crops,” she said.

Emily Symmes

“NOW is ubiquitous, and there is an increased nut crop footprint in California, with more than one million acres of almonds, plus pistachios and walnuts,” Symmes explained. “All play host to NOW, as well as a host of natural plants. This thing isn’t going anywhere. And it was pretty bad in 2017 in terms of harvest damage.”

One of the key factors for higher navel orangeworm damage was not being able to get into the fields because of the standing water.

“There were a couple of other factors as well. Typically, rainfall and moist conditions can help NOW mortality in the winter. We tend to think that it can help rot the nuts and do us some favors, but we have to be able to get out and get the nuts shaken or get pulling crews in and get those things on the ground. And then them being on the ground is not always a sure thing. Sanitation was huge in terms of NOW problems this year,” Symmes said.

Heat units also played a part in the development of more NOW pressure. There were a lot of moths flying around longer and laying eggs.

“It got hot in mid to late June, and it seemed to just not let up. What that meant was, in terms of our degree-day models or the heat unit that drive insect development, it ended up getting pretty far out ahead of what is typical, if there is anything such as typical. But certainly ahead of the last couple of years,” Symmes explained.

By September, we were about two weeks ahead in degree-days and that means that the moths were out earlier. They’re flying around. They’re laying eggs on the nuts when they’re still on the trees.

Symmes stressed that the importance of sanitation is to minimize the site where the NOWs mature.

“It’s really important to remember that sanitation efforts aren’t just directly killing any worms that are over-wintering in your orchard. Yes, it does that. But it also minimizes those sites where your first and second generations are going to develop next year,” she said.

Pistachios Suffer Navel Orangeworm Damage

Overwintering NOW Population Must Be Reduced

By Robert H. Beede, UCCE Farm Advisor, Emeritus

The following is a special report by Robert H. Beede, UCCE Farm Advisor, Emeritus, on the state of the pistachio harvest and the fight against navel orangeworm damage.

Season Wrap Up: It looks like we wound up with about 600 million pounds. Only God knows how many million navel orangeworm got, but you all know it was a bunch! Processors have their hands full delivering the quality nut California is known for. Many growers I speak to ask, “What happened?” From my discussions with many crop consultants, what DIDN’T happen was sanitation! This was not only true for the pistachio growers, but almond producers as well.

Growers barked at me about the wet weather making orchard access difficult to impossible, the size of the trees making sanitation cost prohibitive, and the difficulty in getting the nuts out of the trees. These issues are all true. So, if you decide that you cannot sanitize, then you had best figure out how you are going to run the ranch on pistachios that are 30 to 40 cents less valuable than those with low worm damage.

I know I sound like the donkey’s behind with all the answers, but the pistachio industry needs to join forces with the almond guys to determine what we can collectively do to reduce the overwintering NOW population.

There has been millions spent studying NOW, and I have NEVER waivered on the fact that sanitation is the cornerstone to controlling this beast! I also still think that once we get the kinks out of mating disruption, that everyone should use it as a means to SUPPRESS the population. Note that I did NOT say, “Control it as a stand-alone program,” just in case someone out there wants to stuff words in my pie hole!

We are in DESPERATE need of an effective adult monitoring tool for NOW mating disruption. I hope this comes soon, in order to give pest managers a method of knowing when the pheromone is not reducing mating sufficiently. We also need more research on the cultural and environmental factors affecting the number of early split nuts, which become the NOW link to the new crop at harvest.

Sanitation: Now is the time to begin winter sanitation by removing the nuts that did not come off during harvest. Many of these nuts are blank, but do not assume that all of them are. Research by many good scientists has proven that winter sanitation is the key to breaking the overwintering NOW population cycle, which looms ever greater when the winter is warm and dry. Beginning the season with a large overwintering population simply reduces the effectiveness of your in-season sprays. Although the research has not been done, to my knowledge, the TIMING of sanitation may be a factor in its efficacy.

Nut removal and destruction early in the fall may be more effective, because the percentage of NOW larva in the early instar stages should be greater. This is due to the large peak in egg laying that occurs during hull degradation. Thus, they may be more susceptible to desiccation or fungal attack because of their smaller size. Disturbing their overwintering site from the tree onto the ground early also places more environmental pressure on their survival. This is just my opinion; it may be worthy of investigation.

California Pistachios Are Set For Record Year

California Pistachios Make Comeback in 2016


By Brian German, Associate Broadcaster

California produces close to 99 percent of the nation’s pistachios. With harvest season just about wrapped up, growers are pleased with this year’s crop. 

Last year was a slow one for pistachios, with only 275 million pounds produced.  Because pistachios are alternate-bearing [tendency for an entire tree to produce a greater than average crop one year and a lower than average crop the following year], last year’s disappointing crop allowed the trees to rest before producing this year’s estimated record crop. 

Richard Matoian, executive director, American Pistachio Growers, estimated this year’s crop to be between 830 and 850 million pounds. The last record-setting crop was in 2012 when growers produced 555 million pounds of pistachios.  This year, some California growers have reported broken branches due to the heaviness of the crop, a phenominon Matoian has never seen before.  

Just as last year’s lower harvest enabled the pistachio trees to bounce back this year, increased rainfall last winter helped improve irrigation supplies for the nut trees this year. 

In addition, more chilling hours last winter also helped boost production.  Pistachio trees require cold nights, with at least 800 hours of temperatures below 19 degrees Fahrenheit.  This winter, trees experienced more than 1,000 hours of those conditions. 

Reports indicate that the pistachio crop from Iran, one of our biggest global competitors, is a bit down this year, which could help California growers get a better price for their pistachios.  “We all hope and try to keep the market as strong as it can be,” said Matoian, “but there are market forces at work. You can’t hold on to a crop forever. You have to be conscious of what the world supply is, and so a number of factors go into setting a price.”

Growers are pleased with the overall size of the harvest compared to last year, but they’re also a bit concerned about the prices. “The initial price the growers got last year was somewhere between $2 and about $2.20 per pound. Now we are at a $1.60 to about $1.80 per pound,” Matoian said.