Tomato Spotted Wilt Virus Fights Back

New Strain Creates Challenges

By Mikenzi Meyers, Associate Editor

A new strain of the Tomato Spotted Wilt Virus has created a challenge among vegetable growers, making integrated pest management, or IPM, increasingly critical. Bob Gilbertson, plant pathologist at UC Davis, has insight and advice as to how farmers should tackle this new strain.

“The first thing is to know what’s out in your field. And there’s a good diagnostic test for curly top, spotted wilt, alfalfa mosaic, and other viruses,” Gilbertson said.

Bob Gilbertson

After the virus is confirmed, he encourages growers to explore their options of treatment. Prior to the new spotted wilt virus strain, growers could turn to the SW-5 resistance gene to cure their field. Unfortunately, Gilbertson explained, the new strain actually breaks that resistance, which is where IPM becomes even more important.

In the future, Gilbertson hopes to find additional resistance genes to break the new strain. Until that time comes, he wants to use good IPM to manage it.

Gilbertson further added, “Increased sanitation, removing overwintering hosts, weeds, and bridge crops like lettuce, and then timing the applications of thrips management better, to slow down the appearance of adult thrips that carry the virus,” are all examples of good IPM.

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Curly Top Virus Light In 2018

CDFA Surveys Predict Curly Top Vectored by Leafhoppers

By Patrick Cavanaugh, Editor

Curly top virus is a common disease in California. In its worst years, entire fields have been lost to curly top in the foothills of the Central Valley, and it can infect a variety of plants from a total of 44 plant families as well as 300 individual species.

Curly top commonly affects tomatoes, peppers, beets, spinach, potatoes, and beans, as well as a variety of weeds. A common characteristic of curly top is stunting of the plant as well as curling and twisting of the leaves, where it gets its name, curly top. Leafhoppers are the main vector of the virus.

Currently, the CDFA conducts a yearly curly top prediction where they monitor numbers and the leafhopper population as well as the prevalence of the virus to give a scope of what the upcoming year might look like.

“Curly top virus was very low in 2018 as predicted—based on the amount of virus carried by the leafhoppers and the leafhopper population,” said Bob Gilbertson, Plant Pathologist, Department of Plant Pathology at UC Davis.

“We hope that CDFA will continue to carry out the leafhopper screening for the virus and for the population so growers get a prediction of what the curly top incidents will be the coming year,” Gilbertson said. “It’s good that we can tell growers when there’s going to be a bad curly top year so they can implement additional strategies.”

These strategies include changing where they’re going to plant a field or using timed insecticides, particularly systemic insecticides like the new Verimark (From FMC) insecticide to manage curly top.

“We’ve already found that that material can slow down the spread of curly top in a field,” Gilbertson explained. “So in a year where it’s predicted to be bad—high populations of leafhoppers carrying high amounts of the virus—then you as a grower would then want to consider using some of these insecticide approaches.”

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Almond Band Canker has No Cure

Almond Band Canker Creeping up Again

By Patrick Cavanaugh, Farm News Director

Themis Michailides, a UC Davis Plant Pathologist based at the Kearney Agricultural Research and Extension Center, recently told California Ag Today that almond band canker is becoming a big problem.

“This was a very old disease, and almost forgotten, but now we have major problems, particularly in the young orchards, first leaf, second leaf, third leaf, and it can also be found in six year old trees,” Michailides said.

Band canker is a fungal disease caused by a group of Botryosphaeria fungi that are very common in major crops like grapes, almonds, pistachios, walnuts, avocados, citrus and other crops, so they have a large range.

Band canker establishes itself as a spore inoculum that resides outside and also inside of orchards and waits for the right conditions, which are wetness and also high temperatures.

“It develops first like a ring, a canker that is a horizontal canker on the trunks of the trees and decays the wood and produces sap. It’s a disease that can kill young trees in the orchards,” Michailides said.

“Once you have the cankers developed in the trunks of the trees, there’s no cure, but we can prevent it by managing irrigation, trying to keep the trunks of the trees dry,” he said. “We need to develop protective sprays in order to avoid the development of the disease in young trees.”

“Once we have the water and the temperatures rise above 50 degrees Fahrenheit, the conidia – the spores of this fungi – will germinate and infect vigorous varieties we have now through the growth cracks,” Michailides said.

“It’s getting more serious, especially now, because we see that the disease is uniformly distributed throughout the orchard, which indicates to me perhaps that the inoculum is in the trees and not coming from the outside sources. We don’t see the patterns we saw years ago, where we had the source and then a center of disease close to the source,” Michalides explained.

 

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Postharvest Short Course Focused on Taste and Quality

UC Davis Postharvest Course Covers Food Loss, Produce Handling

By Lauren Dutra, Associate Editor

The 38th annual Postharvest Technology of Horticultural Crops Short Course concluded TODAY, June 24 at UC Davis. Presented by Beth Mitcham, director of the Postharvest Technology Center, the course focused on postharvest produce quality and safety.

Beth Mitcham, Director of the Postharvest Technology Center at UC Davis.
Beth Mitcham, Director of the Postharvest Technology Center at UC Davis.

“This class provided a really broad overview of all the topics that are relevant for postharvest handling of produce, including fruits, vegetables, nuts, and also ornamentals,” said Mitcham. “We cover the crops that are grown in California, but because our audience includes a lot of people from around the world who want to learn the basics about postharvest handling, we also cover a few crops that aren’t grown in California for commercial purposes. Furthermore,”she noted, “we also address some of the latest technologies that are available for maintaining excellent quality,”

Maintaining a good cold chain throughout the entire shipping line is critical, according to Mitcham. “We talk a lot about temperature,” she elaborated. “In fact, we tell students the three most important things about postharvest biology and technology are: temperature, temperature and temperature. We discussed many other technologies during the week, but they are secondary to good temperature management,” she noted.

Mitcham also mentioned food waste and how to control it. “So much effort goes into growing the crop, which includes harvesting at the prime of ripeness and getting it in the pre-cooler, on the trucks and to the market. But, people buy it, put it in their refrigerator and then don’t eat it. It goes bad and they waste it. It does happen,” said Mitcham. “Our goal is to try to make the product as hearty as possible while retaining really good flavor so it can last in your refrigerator as long as possible but also so people want to eat it, so hopefully it doesn’t sit in there and degrade.”
UCD Postharvest Technology Center

In reducing postharvest losses, Mitcham commented on the dissonance between addressing postharvest flavor and consumer satisfaction, “In some ways they are two opposite ends of the spectrum; some of the things we do to reduce losses are counter to delivering good flavor to consumers,” she said. “We really need to do both, and that was a big part of our message this week.”

Also at the event, the California Leafy Green Marketing Agreement (LGMA) discussed food safety principles, and Trevor Suslow, a UC Davis Plant Pathologist with the Postharvest Technology Center, discussed good agricultural practices (GAP) for food safety.

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Helene Dillard Hits Stride as Dean of UC Davis College of Ag  

By Patrick Cavanaugh, Cal Ag Today Reporter

Dr. Helene Dillard, the new dean of the College of Agricultural and Environmental Sciences at UC Davis appointed this past January 2014, commented at the  Produce Marketing Association Annual Meeting last month in Anaheim, that she has very well-defined goals for the students in her department.“One of my goals is to make sure that we are giving our students the very best education that we can possibly give them, and also to help them see envision new career paths,” Dillard. “So many of our students arrive and are not sure what they want to do, but they know that they are interested in food and agriculture.”

Helene Dillard, dean of University of California, Davis, College of Agriculture and Environmental Sciences
Helene Dillard, dean of University of California, Davis, College of Agriculture and Environmental Sciences

Dillard noted that when she left high school, she knew that she wanted to be a scientist, but she had no idea that she would one day become a plant pathologist, working on fungal diseases on lettuce. “We have more than 30 majors in our college, which gives our students so many opportunities,” she said.

“I also want to help our students realize just how big California agriculture is,” said Dillard. “It’s important that they know the breath and depth of the state’s ag industry and help them to appreciate this $45 billion industry,” she said.

Dillard is also interested in internships for students. “I want to make sure our students get their toes in the water for potential jobs and see the high technology involved in  agriculture–that it’s not just about shovels,” she said.

She said students get a lot of hands-on experience at the university, with more than 3,000 acres of farmland for students to work with. “It’s different when you do some experiments on the university farm, versus going out in the real world and do it on a bigger scale. So the goal is to get them to practice on the university farm and then get out to a farm for an internship.

Dillard said another exciting thing about UC Davis is that the university is at a stage where it is hiring a lot of new people. “We currently have 15 active searches for new faculty, which is really exciting as these people come from all over the world,” she said.

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