Navel orangeworm can be devastating for almond and pistachio growers and knowing when and where to spray can often depend on weather. Researchers have been working with state weather services to collect data and determine the best spraying times. Washington State entomologist Dave Crowder discussed these efforts recently with Matthew Malcolm from California Ag Network. Watch this quick video and read more in Pacific Nut Producer Magazine.
Tag: Washington State University
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American Pistachio Growers Awarded $1 Million for Regional Pest Management Collaboration
American Pistachio Growers (APG), in collaboration with Washington State University, University of California – Riverside, UC Cooperative Extension, the USDA Agricultural Research Service and regional nut industry partners, has been awarded a $1 million grant through the California Department of Food and Agriculture’s Biologically Integrated Farming Systems (BIFS) Program to develop a Regional Integrated Pest Management (IPM) network for Navel Orangeworm (NOW) — the most damaging pest in California’s tree nut industry.
The project, led by Dr. Houston Wilson (UC Riverside), Dr. David Crowder (WSU), Dr. Jhalendra Rijal (UC IPM), and Dr. Charles Burks (USDA ARS) will pilot a groundbreaking Decision Aid System (DAS) that integrates real-time trap data, weather models, and crop phenology into a single communication platform. The goal is to improve the timing and precision of pest control decisions while fostering regional cooperation among almond, pistachio, and walnut growers.
“This project moves us beyond the farm gate,” said Joe Coelho, APG’s Director of Sustainability and Member Outreach, who serves as Technical Agronomist and PCA on the project. “For the first time, growers across commodities will have access to shared regional data and communication tools that allow them to anticipate pest pressure before it hits their fields and ultimately make precise, timely treatment decisions. The outcome is fewer sprays, lower costs, and higher quality nuts.”
Through field-level data acquisition, the system’s meta-analytics will identify regional flight trends coupled with crop-specific phenological development and enhance forecasting of NOW flights — critical steps in breaking the pest’s lifecycle across neighboring farms. Ultimately, the program is expected to help reduce pesticide use, improve nut quality, and lower aflatoxin risk associated with pest damage.
APG will serve as the grower administration partner, coordinating grower participation and outreach. Carlee Branco, APG Grant Programs Administrator, will conduct on-farm grower coordination, engagement and data collection. “This is a major milestone for sustainable pest management,” said Coelho, “and it demonstrates APG’s leadership in advancing research that directly benefits growers.”
The Regional IPM for Navel Orangeworm Project represents a pivotal step toward the state’s Sustainable Pest Management (SPM) Roadmap by providing a scalable, data-driven framework that can be expanded statewide.
“This is exactly the kind of innovation California agriculture needs,” said Dr. Wilson. “Regional coordination is essential to long-term pest reduction, especially for highly mobile insects like the navel orangeworm, and this project will now put those ideas into practice at scale.”
The program launches in early 2026, with pilot regions in West Fresno County and Modesto, serving as the foundation for a future statewide expansion. Growers within these territories who are interested should contact Carlee Branco for more information at cbranco@americanpistachios.org.
American Pistachio Growers (APG) is a non-profit trade association representing more than 800 growers and processors across California, Arizona, and New Mexico. APG’s mission is to enhance grower profitability through global marketing, industry research, and sustainability initiatives that promote economically viable and environmentally responsible pistachio production.
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Honey Bees at Risk for Colony Collapse from Longer, Warmer Fall Seasons
The famous work ethic of honey bees might spell disaster for these busy crop pollinators as the climate warms, new research indicates.
Flying shortens the lives of bees, and worker honey bees will fly to find flowers whenever the weather is right, regardless of how much honey is already in the hive. Using climate and bee population models, researchers found that increasingly long autumns with good flying weather for bees raises the likelihood of colony collapse in the spring.
The study, published in the journal Scientific Reports, focused on the Pacific Northwest but holds implications for hives across the U.S. The researchers also modeled a promising mitigation: putting colonies into indoor cold storage, so honey bees will cluster in their hive before too many workers wear out.
“This is a case where a small amount of warming, even in the near future, will make a big impact on honey bees,” said lead author Kirti Rajagopalan, a Washington State University climate researcher. “It’s not like this is something that can be expected 80 years from now. It is a more immediate impact that needs to be planned for.”
For this study, researchers ran simulations through a honey bee population dynamics model using climate projections for 2050 and the end of the century at 2100. They found that honey bee colonies that spend the winter outside in many areas of the Pacific Northwest would likely experience spring colony collapses in both the near- and long-term scenarios. This also occurred under a simulation where climate change continued as it is progressing now and one where greenhouse gas emissions were reduced in the near future.
Worker honey bees will forage for food whenever temperatures rise above about 50 degrees Fahrenheit. When it gets colder, they cluster in the hive, huddling with other bees, eating honey reserves and shivering, which helps keep the bees warm. In the spring, the adult worker bees start flying again. That means they also start dying. If too many older worker bees die before their replacements emerge ready to forage, the whole colony can collapse. Scientists have estimated this happens when there are fewer than 5,000 to 9,000 adult bees in the hive.
This study found that colonies wintering outside in colder areas like Omak in the far north of Washington state might still do all right under climate change. But for honey bee colonies in many other places, like Richland, Washington near the border of Oregon, staying outside in the winter would mean the spring hive population would plummet to fewer than 9,000 adults by 2050 and less than 5,000 by the end of the century.
The authors note that the simulations just looked at seasonal factors like temperature, wind and the amount of daylight, making them fairly conservative models.
“Our simulations are showing that even if there is no nutritional stress, no pathogens, no pesticides — just the conditions in fall and winter are enough to compromise the age structure of a colony. So when the hive comes out of winter, the bees are dying faster than they’re being born,” said co-author Gloria DeGrandi-Hoffman, a research leader at the U.S. Department of Agriculture’s Carl Hayden Bee Research Center.
The researchers also simulated a potential mitigation, placing honey bee hive boxes in cold storage so the bees start to cluster earlier and save workers. For instance, in the Richland scenarios, by the end of the century, having bees in cold storage from October to April would boost the spring hive population to over 15,000 compared to around 5,000 to 8,000 if they were kept outside.
A relatively new practice, cold storage is gaining popularity among commercial beekeepers to help manage bee health and for the logistics involved in moving hives to California to pollinate almond trees in February, an event that draws more than two million hives from across the country.
“A lot of beekeepers are already practicing this management technique of storing bees indoors because it has a lot of immediate potential to help in a number of ways,” said co-author Brandon Hopkins, a WSU entomologist. “These findings demonstrate that there are additional benefits to this practice for the survival of colonies in a changing climate.” This research received support from the Washington Department of Agriculture’s Specialty Crop Block Grant. —
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Invasive Stink Bug Habitat Could Expand with Climate Change
A foul-smelling, voracious, wide-spread pest of fresh fruits and tree nuts could become even more ubiquitous with climate change.
A recent modelling study found that changing weather could increase suitable habitat for the brown marmorated stink bug in the United States by 70%. The study, published in Pest Management Science, draws on data from a three-year stink bug monitoring effort in 17 states as well as several potential climate scenarios. However, whether the insects will thrive in new places depends on the conditions of each area and potential mitigation measures.
“Every system will change with climate change, so the fact that you can grow garbanzo beans, lentils or wheat without these pests now, doesn’t mean that you will not have them in a few years,” said study lead author Javier Gutierrez Illan, a Washington State University entomologist. “There are mitigating things that we can do, but it is wise to prepare for change.”
The study found that overall, there is likely to be a northward shift in stink bug-friendly conditions. Regions that may be particularly affected include the Mid-Atlantic, areas surrounding the Great Lakes, and the valleys of the West Coast, such as the Sacramento Valley in California and the Treasure Valley in Idaho.
The brown marmorated stink bug is a generalist herbivore — it is known to feast on nearly 170 different plants including crops and ornamental plants. Originating in Asia, this type of stink bug first appeared in the U.S. about 20 years ago and has since spread coast to coast. It’s been detected in 46 states and considered a pest in 15 of them.
Brown marmorated stink bug on a blackberry plant. Photo by Gheorhge on iStock Homeowners may recognize brown marmorated stink bugs because they like to overwinter indoors. In fact, the study found that proximity to populated areas appeared to help the insects get established in new places, but once there, they did not need to be near people to proliferate. Other factors like availability of water mattered more for their abundance.
People are likely inadvertently transporting stink bugs in vehicles or farm equipment to areas that would otherwise be hard for them to reach by flying alone, said Gutierrez Illan.
Stink bugs dislike cold winters, but the rising temperatures brought by climate change are not necessarily a good thing if the land becomes too dry. They need water, so the researchers said that changing patterns of precipitation will likely influence where the stink bugs will thrive.
In some states including Washington, officials and researchers are employing a parasitoid insect, called the samurai wasp, to control stink bugs. The wasps lay their own eggs inside stink bug eggs. This not only destroys the affected eggs, but when the wasp larvae hatch, they eat other developing stink bugs. Measures like these might help prevent or minimize stink bug spread into new areas, Gutierrez Illan said.
For Washington growers, the researcher recommended using WSU’s DAS, or Decision Aid System, a web-based tool which provides information to help prepare for changes to their agricultural systems, including the possible appearance of these pests.
Gutierrez Illan also advised growers to familiarize themselves with the brown marmorated stink bug through sites like stopbsmb.org, even if they have never had the pest in their fields.
“Most growers learn from their parents or from the previous generation, but the information that they had is probably no longer as useful because the climate is changing, so they need these types of tools,” Gutierrez Illan said. —
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New Asian Giant Hornet Guide to Help Beekeepers
Beekeepers have a new resource if they suspect the invasive Asian giant hornet is attacking their honey bee colonies.
Two Washington State University scientists wrote Distinguishing Asian Giant Hornet Damage to Honey Bee Colonies, a free-to-download publication from WSU Extension.
“We want to dispel some of the fear that beekeepers have been feeling around Asian giant hornets,” said Kelly Kulhanek, a postdoctoral researcher in WSU’s Department of Entomology and lead author of the publication. “Our goal is to help them identify specific symptoms of giant hornet attacks and distinguish between that and something with similar damage.”
It’s important to note that, to date, there have been no confirmed honey bee colony losses in North American because of giant hornets, sometimes referred to as “Murder Hornets,” according to Kulhanek and her co-author, WSU associate professor Brandon Hopkins.
“We assumed from all the media reports about the hornets that we would be getting frequent reports of attacks,” said Hopkins, a scientist on WSU’s honey bee and pollinator program. “And we have, but they’ve all been colonies killed by other things.”
The most noted symptom of an Asian giant hornet attack on honey bees is headless bees. But other hornets, such as yellow jackets, cause similar damage to colonies. Other animals do as well.
Hopkins saw that first-hand in a colony at the WSU Honey Bee & Pollinator Research, Extension, and Education Facility in Othello.
“When we started keeping bees near the new facility, we noticed dead bees with their heads torn off and thorax chewed out,” he said. “But we found it was caused by mice.”
Hopkins believes the mice were feeding on bees that died naturally and were already on the bottom boards of the colony boxes, or on the ground outside the hive entrances.
The new publication talks about more specific signs that bee deaths are caused by Asian giant hornets. There are two phases to their attacks. Phase one is picking off individual bees and carrying them back to the hive to feed on. During this phase, no dead bees are left around the colony because they are carried away to another location. The second is called the “slaughter phase,” when a bunch of hornets show up at the hive to feed on and decimate the colony.
“We’ve learned from Asian giant hornet experts that if there are dead bees around a hive, but there are no signs of the hornets, then it’s probably not Asian hornets,” Kulhanek said. “By the time the slaughter phase happens, it’s super obvious and too late to do anything.”
Another note involves geography. Asian giant hornets have not been spotted in North America outside of a few locations in Northwest Washington and Southern British Columbia.
“I’ve gotten texts from beekeepers from as far away as North Dakota concerned their colony had been attacked by Asian giant hornets,” Hopkins said. “I tell them that’s not really possible for several reasons.”
Beekeepers in areas where the invasive hornets have been found can take precautions, detailed in the publication, such as restrictive netting or screens around the entrance to a colony.
“The hornets are very large compared to bees,” Hopkins said. “There is promising research on defensive netting that bees can get through but the hornets can’t.”
That wouldn’t stop the first phase, when invaders pick off individual bees coming and going to the colony. But it would dramatically slow or stop the slaughter phase, when hornets enter a colony.
WSU entomologists has heard from experts in the hornets’ native range. In Thailand, for example, beekeepers sometimes hire school-age children to swat hornets flying around their colonies with badminton racquets.
“Beekeepers should be extremely cautious when approaching a colony if they think Asian giant hornets are present,” Kulhanek said. “After the slaughter phase begins, the hornets will become very defensive of the hive and will attack anyone who approaches.”
The best hope for the broader beekeeping community is eradication of the invasive goliaths. To that end, the WSU researchers urge beekeepers to report any suspected sightings to the Washington State Department of Agriculture.
“Asian giant hornets are new and scary and have gotten a lot of attention,” Hopkins said. “But they create similar problems and damage as yellow jackets and other predators. Take preventative measures and keep an eye out. That’s the best thing you can do.” — By