By Kathy Coatney

Overproduction is the single most common problem with California summer squash, according to Mark Gaskell, University of California Cooperative Extension farm advisor for small farms and specialty crops in Santa Barbara and San Luis Obispo counties.

One way to get around the problem is to harvest the squash at non-traditional times.

According to Gaskell, the problem is everyone else is planting summer squash at the same time, so there is a glut on the market at harvest, which in turn, makes for chronically low prices. Gaskell said he believes there are times of the year when growers can be profitable with squash, but it tends to be early or late in the season when volumes are lower.

"We have a fair number of small scale growers who work on strawberry farms during the strawberry season, then they'll kind of bridge over between strawberry crops by growing squash and some of the other warm-season vegetables during the summer," Gaskell said.

The best time to plant is when prices are really low. Gaskell suggests growers plant squash according to the market and not plant according to when they're accustomed to planting.

"I encourage them to look at market price histories and try to harvest at a time of the year when the price is higher," Gaskell said. "We've had several grower meetings where we show growers price histories and show them how to use market signals as an indication of when to plant. The more successful ones do that, and the other ones don't." 
Todd Hirasuna, general manager of Sunnyside Packing Co. in Selma, agreed overproduction can be an issue in summer squash.

"We've been doing it long enough now that we kind of know what our customer base is, and how much we can produce and be OK with," Hirasuna said, adding farmers can be forced to take some out of production if the market conditions go bad.

Mosaic virus can be a problem for summer squash, Hirasuna said, adding chemical treatment is generally effective. There are three major forms of the virus: cucumber mosaic, watermelon mosaic and zucchini yellow mosaic.

Genetic improvements by the seed companies have resulted in varieties that are resistant to mosaic viruses, Hirasuna continued.

"You can't really get away from treating, but you can tolerate a little more pressure," Hirasuna said, adding resistant varieties allow the plant to get nicked up a bit and still not show symptoms.

"I've seen in the last probably two years, more of a presence of mosaic in the springtime than years previous," Hirasuna said.

"Typically warmer temperatures will bring on the vectoring insects, the aphid, the white fly," Hirasuna said, adding this increases problems with the mosaic virus and makes fall planting more challenging.

Powdery mildew can be a problem in the fall.

"I think where we're at it's not a strong enough form of powdery mildew to really take you down," Hirasuna said, adding typically in the spring he doesn't see as much.

For the most part Hirasuna packs four sizes of summer squash. "The smaller sizes go to mostly retail, and the larger sizes go to food service, but as far as doing any freezer or anything like that, we don't," he said.

Marita Cantwell, a post-harvest specialist with UC Davis, has worked on summer squash. 

"We did evaluate a range of varieties for chilling injury and then also for water loss," Cantwell said. 

Cantwell studied about 30 varieties of summer squash and she found each variety has its own ideal chilling temperature.

"There are specific temperatures at which you can maximize their shelf life to maintain their quality best," she said. "When summer squash is stored at too low a temperature, beyond about a week or so, then there may be chilling injury symptoms. We do see that periodically."

Cantwell said when squash has been stored at too low a temperature, for too long, there will be signs of decay. 

Squash tends to be stored at too low a temperature, Cantwell continued. The reason it is kept at lower temperatures is to prevent water loss, she added.

"That's one of the incentives for people to store them at lower than recommended temperatures, because you minimize the water loss even more," Cantwell said.

The problem with this is, reducing the temperature solves one problem while creating another, Cantwell continued. "You're reducing the water loss, but now you're causing the chilling injury."

Ultimately, there is some give and take on both ends, Cantwell said. "If you have good packaging, then you'll reduce the water loss, so there's really not an incentive to store them at below recommended temperatures," Cantwell said.

In terms of post-harvest losses, mechanical or physical damage during harvest is the biggest problem, Cantwell said. Poor handling, grit in the buckets and on the packing tables, scuffing during packaging, the squash touching each other, and vibration during transport can all increase damage to the squash, she added.

Water loss would also account for post-harvest losses, Cantwell said.

The more summer squash is handled, the more scarred and bruised it becomes, Hirasuna said.

Summer squash is still hand harvested, so it can be easily damaged with excessive handling. To reduce this, Hirasuna invested in a machine that's similar to a romaine heart lettuce harvester.

"Basically it's a 64-foot-long, self-propelled packing line," Hirasuna said.

The crop is packed in a box before it even leaves the field, Hirasuna said, adding this reduces the amount of handling and makes for a higher quality product.

Direct pack in the field helps reduce the damage, Cantwell said, and minimizing the number of transfers should produce a product with less physical injury.

"Another general rule in post harvest is the more times you touch a product, the more you're going to damage it," Cantwell said.

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(Kathy Coatney is a reporter in Corning. She may be contacted at kacoatney@gmail.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation 
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