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.

Caltec Shares Innovative Pest Control Practices

A New Approach to Managing Vine Mealybug

By Hannah Young, Contributing Editor

Some innovative pest and disease control products, such as heat application to kill insects, are making their way to the market, according to Caltec.

California Ag Today spoke with Rudy Monnich, president of Caltec Ag, about some of the new ways California farmers are fighting pests.

caltec
Rudy Monnich with Caltec

“We have a product which is the diatomaceous earth that controls vine mealybugs and ants and mites in orchards and vineyards,” Monnich said, adding, “There is nothing more damaging than vine mealybug. In fact, Monterey County is forming a committee to be zero tolerant just for that insect pressure.”

The product is silica dioxide and will scarify the body of insects, dehydrate them, and in result kill them off in three or four days, Monnich explained.

However, the product is not a chemical, but a mineral, which significantly diminishes resistance issues.

“You don’t have the resistant issues build up,” Monnich said. “It’s also controlling thrip and whitefly in tomatoes.”

Caltec introduced the product this past spring.

Heat application can also be used by growers to combat insect problems.

“We are working with the Agrothermal people who have a machine that 300-degree to 400-degree temperatures will annihilate soft-bodied insects in tomatoes and powdery mildew in grapes,” Monnich said.

The application of heat kills the spores before signs of damage appear on the plant, Monnich explained.

This method of pest control is increasing the quality of wine, Monnich concluded.

Spotted Wilt Virus Impacting Tomatoes Again

Virus has Gotten Past Resistant Gene

By Patrick Cavanaugh, Editor

Tomato spotted wilt virus is becoming big in the central San Joaquin Valley, according to Tom Turini, University of California Cooperative Extension Farm Advisor in Fresno County for vegetable crops. The virus had earlier been spotted in lettuce, and this has caused some concern in this season’s tomato crop.

Tom Turini

“We had some concerns early in the season that we might be looking at a year where it’ll become a challenge, because we were finding it in lettuce back in February and March in the Huron area,” Turini said. “And then we notice that tomatoes were showing the virus symptoms. We had been managing tomato spotted wilt in processing and fresh market tomatoes largely with a resistance gene, and it seemed that the resistance was breaking.”

The virus is spread by thrips, and the gene in the tomato was the biggest deterrent in combating thrips.

“We were also talking about an IPM program, but the industry was leaning on this gene. This gene became a big part of their spotted wilt prevention program,” Turini said. “While sanitation of weeds was practiced, and there was some thrips management, it was really dependent upon this single gene resistance in the tomatoes, and as of 2016, we saw evidence that that gene was no longer performing.”

Because the virus can wipe out entire tomato fields, researchers are scrambling to find a new way to deter the thrip spreading the virus on tomatoes.

BioSafe Systems Offers Biological Control Products

BioCeres Beneficial Fungi Kills Important Pests

By Patrick Cavanaugh, Farm News Director

California Ag Today recently interviewed Jay Sughroue, Ph.D. with BioSafe Systems about the new BioCeres WP Biological Pesticide.

BioCeres is new strain of the fungi Beauveria basiana discovered in Italy in 1815. There was a sharp decline in silkworm production and the entomologist back then, Antonio Basiana, discovered  the fungi  that was responsible for white muscarsdine disease causing the decline of silkworm production.

“The new strain, ANT-03, is different from commercially available strains is that it’s more aggressive and more resilient, so it lasts longer in the environment. And it’s more pathogenic when it comes in contact with insects that you want to control,” Sughroue said.

“Fast forward several decades, and now, we have commercially available products that are controlling very important agronomic pests, such as thrips, aphids and white flies,” Sughroue said.

Sughroue noted that it’s important to follow important application strategies.

“You want to apply this prior to high population development. It’s not a knockdown, so you want to be out there scouting fields. As soon as you start to see numbers that are indicative of causing damage, you want to start a spray program that contains BioCeres, and then after about 5 to 7 days, you’ll start to see the pests decline in population.”

The fungi spore germination is the key to the effectiveness.

“The spore lands onto an insect. It doesn’t matter if it’s an egg, a nymph, a larva or an adult. It starts to germinate, and through enzymatic activity and mechanical pressure, it grows inside the insect, and it will start to sporulate so the insects come down with a severe case of the flu. They stop feeding immediately.

Sughroue said while it takes about 3 to 5 days for the pest to die, it stops feeding very soon after the spore germinates inside them.

Sugroue said the list of the pests will only become larger as time goes by

“We’re going to expanding that list to include other important insects, but this is the first generation of this product,” he said.

 

 

ALERT: Immediate Action Needed for Thrips/TSWR

Source: Neil McRoberts

For those who have water and tomatoes:

 

Thrips numbers have increased rapidly in the southern arm of the Central Valley and Tomato spotted wilt virus (TSWV) has been reported in all of the areas we monitor,” according to Neil McRoberts, Assistant Professor, Plant Pathology Department, UC Davis.

There are numerous reports of TSWV symptoms in crops from Stanislaus County down to Fresno and Kings County particularly around the Huron area.

 

The current risk in Fresno County is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 17th.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.  This means you need to take immediate action.

Generation 4 adults are projected to peak on June 11th.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

 

The current risk in the Merced area is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

Generation 3 adults are projected to peak on May 22nd.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.

Generation 4 adults are projected to peak on June 16th.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

 

The current risk in eastern San Joaquin County is lower than in other southern Counties, but we think a precautionary approach is best. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 28th.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.

Generation 4 adults are projected to peak on June 22nd.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.

 

The current risk in Kings County is high and we are recommending that growers who plan to use an insecticide program against thrips/TSWV take immediate action. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4. Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 22nd.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.  This means you need to take immediate action.

Generation 4 adults are projected to peak on June 14th.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.  Treatment in the 14 days immediately following the generation 3 peak date will also be effective.

 

The current risk in western San Joaquin County is lower than in other southern counties, but we think a precautionary approach is best. The current mini heat wave will accelerate thrips development slightly and further bump up thrips numbers.

If you are planning to use an insecticide program against thrips/TSWV this season, you should target the next generation of thrips (generation 3).  If it is not possible to arrange for treatment in time to catch generation 3, target generation 4.

Delaying treatment until later in the season will be much less effective at preventing damage from TSWV.  Coordinated spraying across large areas has an additional effect on thrips populations because it makes it difficult for them to avoid treatment by migrating.

Generation 3 adults are projected to peak on May 28th.  Sprays applied in the 14-day period before this peak date will check generation 3 and delay further population build-up and TSWV spread.

Generation 4 adults are projected to peak on June 22nd.  Sprays applied in the 14-day period before this peak date will check generation 4 and delay further population build up and TSWV spread.

 

The web resource for integrated management of Western Flower Thrips and Tomato Spotted Wilt Virus in the California Central Valley contains two tools to help in disease risk management:  

A Field Risk Index tool uses simple information about field locations, land use, and agronomy to calculate a risk category for tomato crops.  This tool can be used before planting or early in the season to get a heads up about the general risk to a crop from TSWV.

A thrips population projection model, driven by degree-day accumulation at several Central Valley locations, aids in projecting when thrips generations are hatching, developing, and adult numbers are peaking.  This information is used to issue regular updates and provide broad guidelines for timing insecticide sprays to keep thrips numbers low enough to prevent TSWV from spreading.

The research behind these tools was supported by the California Tomato Research Institute (CTRI)

The model was developed in Collaboration with Dr. Len Coop of Oregon State University’s Integrated Plant Protection Center (IPPC).  The IPPC developed and hosts the USPEST web service which is a multi pest multi model tool that provides information on pest development and disease risk for the Contiguous 48 US states using a network of weather stations.