Virus Pressure Hurts Crops this Fall
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Virus Pressure Hurts Crops this Fall

By Patrick Cavanaugh, Editor 

Joe Santellano has never seen such a tough virus year in vegetables. As the farm manager for Sunnyside Packing, Selma, Calif., he works with the company's organic production areas as well with numerous small family farms growing both organic and conventional vegetables. 

"This fall was a tough one in terms of virus pressure," said Santellano. "We had fields that were completely wiped out by virus pressure, while others faced severe pressure. "I've never seen it so bad."

In one Fresno County 38-acre field or organic zucchini, yellow squash, green beans and cucumbers. the virus pressure was tough, yet he was still able to harvest a quality crop. "Yields were fine in the spring crop, but were down in the fall crop." noted Santellano.

Santellano thinks the added virus infection was due to increased aphid pressure.

Because a lot of weed hosts everywhere. "I see a lot of vacant or abandoned fields, such as when orchards and vineyards are removed, and they are loaded with weeds," he noted. "everyone should do their part in keeping their fields, ditch banks and county roadsides clean so that aphids do not build up and infect the nearby vegetable fields".

Sometimes there was more than one virus strain on plants. According to Richard Molinar, UC Cooperative Extension farm advisor, Fresno County, the cucumbers mosaic virus (CMV) was most prevalent along with the squash mosaic virus (SqMV). He also said that he identified some zucchini yellow mosaic virus (ZyMV), as well as the papaya ringspot virus-watermelon isolate (PRSV-W).

Molinar noted that all five of these viruses infect all cultivated vine crops and under ideal conditions can cause a high rate of crop failure and severe economic loses. "Most viruses are of greater economic concern in the late summer and fall, however, we have seen problems as early as May in the Central San Joaquin Valley with ZyMV.

"Except for SqMV, all of the other viruses mentioned above are transmitted by aphids. SqMV is transmitted by the spotted cucumber beetle, which can retain he virus up to 20 days after feeding on an infected plant," said Molinar. Aphids, after feeding on an infected plant, con only retain the ability to transmit these viruses for very short periods of time (minutes to a few hours).

Santellano said he works close with Richard Molinar, as well as Manuel Jamenez, a farm advisor with UC Cooperative Extension Tulare County. "They are both very helpful," he said.

Once the plant is infected, there is no treatment for the virus. Still, it's important to minimize aphid populations in the filed since it only takes seconds for the pest to infect a plant.

"On the organic crops we used organically-approves materials and did a lot of hand-picking of squash bugs, which were also a problem," said Santellano. "We sprayed an insecticidal soap over the top to kill the aphids," said Santellano. "We also sprayed for whitefly this year, which began to build up during the summer. "For the whitefly he used EF300, an organic insecticide made up of different oils, distributed ny Monterey Ag Resources, Fresno.

"We worked hard to keep our fields very clean, especially staying on top of the cultivations to keep the weeds down," said Santellano.

"We also had-spotted mite pressure, and again, we used soaps and oils to fight them," noted Santellano. "The secret to mites is good coverage with a lot of water. We used drop down nozzles to insure coverage under the leaves." Santellano diligently trained his workers to keep their eyes on insect pressure. He requested that they tell him if they saw aphids, squash bugs or anything else that should not be in the field. His PCA, Richard Kajihara of Western Farm Service's Fresno Branch, is also ready to prevent crop damage form pests and diseases. "He is out once or twice a week depending on pressure," Santellano said.

"For many cucurbit growers it was a very hard year," said Kajihara. "Joe didn't have too serious of trouble on his crop because he kept treating the aphids to minimize their flights.

Kajihara has been working with Santellano for about seven years and said he really enjoys being in the field with him. "I always learn something when I'm with him. And I always come out of the field smarter than when I go in," Kajihara noted. He added that Joe is always very friendly and ready to teach you something. "He would have been a great farm advisor," said Kajihara.

Santellano has been with Sunnyside for 23 years and has always been in the field. I love what I'm doing. "I used to be a grower for the company before they hired me to be one of their field man and take care of a lot of their small family growers. Sunnyside is known for its quality pack of many different vegetables including what Santellano is growing such as zucchini, yellow squash, and winter squash including butternut, onions, green beans, cherry tomatoes, and fresh red onions.

"I help out about 150 growers, nearly all of the them small family farmers working on just a few acres up to 60 acres. They are mostly Southeast Asians and Hispanic growers. They grow a lot of cherry tomatoes, which is very labor-intensive crop. Sunnyside buys from them and sales a good cherry tomato pack," said Santellano.

Santellano said he works with his growers as a consultant to help them know what to look for. "These are mostly conventional growers and I let them know what pest control products are available and then I get recommendations from a PCA, because they have the knowledge base," he said.

He noted that he also holds educational meeting for his small growers. One ongoing topic is nematodes, and stress the fields must be checked before planting. "We show the growers the nematodes on roots under a microscope so that they can be aware of them. If its sandy ground that just had trees or vines planted there, then there is definitely going too be a nematode problem," said Santellano.

Growers typically use Vapam at preplant. They put the material through the drip line under plastic mulch. "We have Steve Hardgrave with AmVac, the distributor of Vapam, come out and show us the safety precautions in using the material," noted Santellano.

While the fall season was very difficult for many growers, many of them learned the importance in keeping the aphid weed host down, noted Santellano. "This was my first year in growing organic vegetables, and it was quite a challenge, yet rewarding," he said.

Last Updated Saturday, June 24, 2017 - 04:19 PM.