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.

Navel Orangeworm Prevention Critical

High Navel Orangeworm Numbers Statewide

By Jessica Theisman, Associate Editor
mycotoxins
Bob Klein

Almonds are deep into hull split, and it is absolutely critical to control any damage from navel orangeworm (NOW), the number one pest in almonds and pistachios. California Ag Today spoke with Bob Klein, manager of the California Pistachio Research Board, about the issue.

“One of the big control strategies for NOW should have happened many months ago during the winter, such as cold sanitation,” he said.

Pest programs start with orchard sanitation. Many growers are lax on sanitation or spend low amounts.

“Those who do stringent jobs are spending $200-$250 an acre on sanitation. And so growers need to be prepared to pay that as far as insecticide applications,” Klein said.

Critical questions that need to be addressed are what you are going to choose to apply and how you are going to time it. When growers are gearing up to put on protective sprays, there are things to remember to increase efficacy. There are always ways in which application can be improved.

If you have a ground rig with fan sprayers, you can get a high kill rate on the lower canopy. You may have to make multiple applications to be able to penetrate the higher portions of the trees.

“You need to look at where your NOW is and maybe make multiple applications. So you can cover both the lower two-thirds of the tree and the top third,” Klein said.

Mycotoxins are Serious Business

Sanitation Fights Mycotoxin Infections

By Jessica Theisman, Associate Editor

In nature, there are fungal metabolites called mycotoxins, and some of them can infect crops. However, certain cultural practices can eliminate them. California Ag Today recently spoke with Bob Klein, manager of the California Pistachio Research Board, based in Fresno, about the topic.

“We see mycotoxins as a result of fungal infection that comes from the Navel Orange Worm. It is damaged predominantly, and if a crop is contaminated with possible mycotoxins, such as one known as Aflatoxn, it can hurt exports. Over 70 percent of our crop is exported, and some of our major markets are very sensitive to a mycotoxin contamination,” Klein said.

“The best programs start with orchard sanitation. Many growers are lax on sanitation or spend low amounts of money,” he explained. “Those who are frugal are spending $200-250 an acre on sanitation, and so growers need to be prepared for that.”

As far as insecticide applications, look at the growers’ data, not what is published in replicated field trials.

“More sprays are better than fewer sprays,” Klein said.

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.

Push Back NOW with Orchard Sanitation

Part One of a Series

Orchard Sanitation Critical This Season

By Patrick Cavanaugh, Farm News Director

We recently spoke with Emily Symmes, the UC Area Integrated Pest Management farm advisor for the Sacramento Valley in statewide IPM program. She told California Ag Today about few reasons as to why Navel Orangeworm damage was so devastating this year, costing tree nut growers at least $137 million.

UC Cooperative Extension Integrated Pest Management Advisor, Butte County
Emily Symmes, UC Cooperative Extension Integrated Pest Management Advisor, based Butte County.

NOW is ubiquitous. And the nut crop footprint in California is larger, with one million acres of almonds, along with pistachios and walnuts up and down the San Joaquin valley.

“The pest is not going anywhere,” Symmes said.

“We had a lot of unique circumstances. The amount of rainfall we got in late 2016 into 2017 was unprecedented and led us into a bad navel orange worm year because growers couldn’t get out and sanitize their orchards”

“Growers were not able to get into their orchards because of standing water,” Symmes explained.

Also, 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 the nuts shaken or get pulling crews in and get the mummies on the ground and destroyed,” Symmes said.

Heat units also played a part in the development of more NOW.

“It got hot. And it seemed to just not let up. Our degree-day models, or the heat unit that drive insect development, ended up getting pretty far out ahead of what is typical,” Symmes explained.

“By September, we were about two weeks ahead in degree-days, and that which meant moths were out earlier. They’re flying around. They’re laying eggs on the nuts when they’re still on the trees, and we are talking almonds, pistachios and to a lesser extent, walnuts.”

Symmes said 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. But the other thing that it does is it minimizes those sites where the first and second generations are going to develop next year,” she said.

Despite all these circumstances as to why NOW was serious this this year, it is critically important to start orchard sanitation as soon as possible. It may not be a good idea to wait for rain and fog to help loosen the nuts this season.